Geared Nameplate

A quickie today – over the weekend, I decided that my workshop at work needed a nameplate outside the door, to make it a little easier for folks to find me. So I put together this design in Fusion 360, and printed it in black and white PLA+. (The “grey” of the gears is a single later of white PLA on top of black gears).

The gears have 8, 9, 10, 12, 14, and 16 teeth, and are symmetrical left/right. This means that it takes 630 revolutions of the smallest gear to return the arrangement to its starting place. We determine this by finding the least common multiple of the number of teeth, which is or 5040. Divide that by the 8 teeth on the smallest gear, and we get our 630 revolutions to return to where we started.

The design has two chamferred holes for screw-mounting, but it’s currently just stuck on the wall with sticky-tack.

Reverse Engineering and Replacing an Industrial 7-Segment Display – Part 1, Research

Building one-off hardware is one part inventing, one part dissecting, one part scrounging. When we try to hit that magic mixture of good, fast, and cheap, so often we must rely on prebuilt modules – if we’re trying to build a widget that gets us from zero to 100, it may only be financially/temporarily/technologically reasonable if someone already makes a module that gets us from 0 to 80. Utilizing economies of scale of already-developed parts can bring a one-off project from the realm of fantasy into feasibility.  Often, the solution is to develop a chain of off-the-shelf components that can fulfill the end goal.

But all components have a service life, and a manufacturing lifetime. And when your part goes out of production and then your spares-bin runs dry, sometimes keeping your machine running requires some deeper problem solving. When you work in the public-facing technology sphere (theatre, museum work, retail displays, etc), a lot of the solutions are literally one-of-a-kind, even if they’re constructed from commercial parts.

I recently had the need to replace a very specific module in some equipment. While it didn’t end up being the most high-tech/high speed/highfalutin bit of technology, it presents a good opportunity to talk through how one can approach an unknown part, come to understand its workings, and develop a replacement. So in this N-part series, we’ll look at the process of researching, developing, and implementing a custom one-off solution to a failed part in a unique piece of gear.

The Lascar EM32-4-LED is a four-digit seven-segment panel mount LED display meant for general-purpose data display. Its small digit size (.39″ tall), machined aluminum housing, small footprint (32.5mm diameter punchout) and NEMA 4X/IP67 made it a compact choice for anyone needing to display a single value with 4 digits of precision. It also had the ability to drive four external LEDs, for additional status or process indicators.

Lascar Electronics EM32-4 LED

A piece of equipment I’ve been working on recently had just such a LASCAR display installed a few years back to serve as a timer. I”m going to have to be a little vague about the specifics of the equipment itself, but since this post is focused on technical process and not the piece itself, I think I can safely share enough details for the following to make sense:

The piece is an interactive object that triggers some actions and servos, demonstrates a physical phenomenon, and then takes about 25 seconds to cool back down before can be used again. The user is presented with a green illuminated button to activate the system – when the system is in active or cooling down, the illuminated button turns red. But because it’s not entirely clear from the action of the device alone when it will be cool enough for use, a countdown timer (two digits) is displayed on the EM32 display, counting the number of seconds until we’re good to run again.

Sadly, this particular EM32 display died shortly after LASCAR decided the product hit its End of Life. What’s more, I’m currently without the ability to modify the programming of the PLC that’s driving the whole shebang. In order to maintain the functionality of the piece, it became necessary to build a device that would ingest the existing signals being sent by the PLC, interpret them, and drive a newly crafted 7-segment display of some kind.

The ‘datasheet’ for the EM32-4 is a paltry 2 pages long. Presumably there was additional documentation provided to those who were using the device, but since it’s now EOL, that documentation seems to be unobtanium. But the existing pair of pages does contain some useful information.

We’ll start at the very beginning (a very good place to start): the opening prose paragraph:

This is where we find a high-level overview of the part, it’s intended purpose, and (sometimes) explanations of the differences between any variants of the part. Say, for example, a given part is made in a standard and a mil-spec version, or a normal and a slew-rate limited version, a manufacturer will often encompass them in a single datasheet. It’s important to identify specifically what part you have, so you can characterize it accurately. 

In our case, the EM32-4 is unique enough that there are no major variants. The paragraph mostly tells us what we already know – it’s a 4-digit, 3 decimal point display in a metal bezel. But it does call out the “optional external LEDs.” While it’s unclear at this point exactly what this means, it’s useful to make note of these surprises early on, as they’ll often explain a what-the-heck-is-that moment late in the datasheet.

Moving on then to the next useful block in just about any datasheet; the electrical specifications. This is where you’ll find input-voltage ranges for power and signals, output voltages and timing, and other device-specific characteristics (transistor beta and voltage spreads, op-amp gain and slew rate, power ratings, etc). If I was doing a Double Dare Physical Challenge and had to utilize a part with only one table of its datasheet available, I’d take the electrical specs chart 9 out of 10 times.

In our case, there’s only 6 lines, but 6 important lines they are. We learn that this is a 5V part, but can run at up to 9V so we can’t assume we’ll have 5V power available. Nominal power  usage is ~20mA, so the power available on existing supply lines may be limited. The operating and storage temperature ranges are typical. VLED is a a bit confusing – does this refer to the display itself, in which case we have no real purpose for this voltage? Or perhaps it refers to the voltage available for the external LEDs. 

The final line is promising – that the typical clock input frequency is 500KHz. This is the first we’ve seen any information about how this device receives communication from a controller. But now we know it’s some kind of clocked input (perhaps sometime like SPI?), and that its possible frequency is not unreasonable from something we might interpret with off-the-shelf hardware. Not that 500KHz is a stroll in the park, but it’s not in the many-megahertz range, say.

The last really useful part of the datasheet is the Functional Block Diagram. This block shows a symbolic representation of what’s happening inside the device, as an aid to the user in visualizing what’s happening on the interior and how we need to interface with it. You really only see this with integrated circuits or other modules (the functional bock diagram of a transistor would be… just a transistor).

To highlight the purpose of the block diagram, let’s do a quick comparison between two drawings on another part: the venerable 555 Timer IC. Its datasheet sports both a schematic diagram and a functional diagram; here are the two side-by-side:

This demonstrates pretty clearly the distinct purposes of the schematic diagram versus the functional one. The functional diagram is there to give users a high-level understanding of how the device functions, where inputs and outputs attach, and what the essential parts of the device are. The schematic diagram is there for those who need to really drill into exactly how the chip is built, because of some precise technical reason. When I’m driving a car, I need to know whether the transmission is manual or automatic, two-wheel vs four wheel, and so on – a functional understanding is enough. A mechanic needs a schematic showing the various linkages and gears of my transmission to diagnose and repair issues; holding that level of information in my head all the time would get in the way of the business of driving around.

With that diversion hopefully making clear the purpose of the functional block diagram, let’s check out the one for the EM32-4.

There’s some really good info here! Let’s start with the external connections:

  • We could have guessed V+ and 0V are supply voltage and ground, but this confirms it.
  • The 35-bit shift register is intriguing, and illuminates the purpose of the D (Data) and Ck (Clock) terminals. There’s also an Ē (enable) pin for the data line which is active low (indicated by the bar over the pin name, for “not”). 
  • Since we don’t have direct control over the latches or buffer layer of the shift register, it seems that data will be shown as soon as its clocked in.
    • There’s a weird hanging inverter on the left side of the diagram attached to the output buffers, as if there was some kind of external buffer control possible at some point. How odd.
  • It seems that the  VL pin is on the downstream side from the voltage regulator, so it probably puts out the 3 volts listed under electrical specifications above.
    • This probably means that L1 thru L4 are open-collector outputs, so we have a sense of how we might use the part to drive the external LEDs.
  • Finally, there’s a Reset pin for soft-resetting the data displayed – this would be useful if the end product was configured so the displayed retained power when the controller turned off – the controller could simply reset the display (or many displays in parallel) to ensure that no data was present for a fresh start.

One of the starting placing for replacing this display was the possibility that there might be some driver circuitry driving a generic 7-segment display. If the display itself was still good, perhaps we can simply replace the driver and have a visually identical display. Those hopes were dashed, however, when I opened up the EM32-4 LED to find…

An OEM 4-LED – the power behind the throne – it’s the same product, right down to the block diagram, but in a DIP-style package. The EM32-4, it turns out, is the OEM-4 with a nice aluminum case and terminal blocks. And the back of the OEM-4 is epoxy-blobbed together, so even if we were to break into the thing, there’s a good chance everything is wirebonded all the way to nowhere and back. Reusing the display on this thing is a non-starter.

All is not in vain, however – the OEM-4’s datasheet is a whopping four pages to the EM32’s paltry two. The first two pages are essentially identical (which makes sense, since one is the other in a very real way), but the two additional pages in the OEM-4’s datasheet have four additional juicy diagrams. Starting with a timing diagram:

We can now see in much more detail that, yes indeed, the display is based around an internal shift register architecture, with bits being clocked in and held in the device. We can see that there’s a start bit (“1”) and the 35 data bits we saw in the EM32’s datasheet, so we’ll need to clock 36 physical bits into the device, whereupon it will automatically load the data (presumably into the data latches and output buffer). Then in 30 ns it will automatically reset and be ready The clock timing, which is listed as 500 Khz nominal, can in theory be pushed to 2 MHz if the 500 ns cycle time (250 ns + 250 ns) can be believed. (Not that we’re hoping it’s that high). We can also get some detail about the external reset signals and the data input timing.

Remember, all this sleuthing is with a goal –  not of driving an EM32, but of creating a display controller which takes the place of an EM32 in a specific installation. Any details we can deduce from the datasheets will help us narrow down where we begin with our investigation of the controller itself.

The “applications” diagram gives us a few pointers – not all are useful to our goal, but are interesting nonetheless. As we guessed before, the LED1 through LED4 pins are open collector drivers – but unlike our guess, we actually need to provide the +3 volts for that control from an external regulator, not from the VLED pin. And the typical current should be 2.5mA per LED, so there’s aren’t high-current drivers in any sense. We can also see that the OEM-4 module has an option for external brightness control via a 50kΩ potentiometer, but we don’t have the ability to access those pins on the EM32 unit.

There’s also a sneaky note at the bottom of the diagram that there is a ‘special version’ OEM-4 LED with a built-in 3V regulator and brightness control. I wonder which version we have?

At first blush the circuit diagram appears to tell us what we already know – there’s a shift-register LED driver inside this thing that’s taking clocked data in and driving LEDs on the downstream side. But there are actually two key things to note here – while I had assumed the VLED pin was only for the external LED’s, it’s actually the anode connection for all the segments of the display! This means that connecting it isn’t optional for driving external LEDs, it’s mandatory if we want the OEM-4 to work. Looking back at the block diagram from the EM32, we can understand the purpose of the built-in regulator shown there.

The EM32’s built-in 3V regulator on the EM32.

The second key thing we learn from the circuit diagram is which bits control which segments. But it’s made even more clear in the final diagram from the OEM-4 datasheet: the serial data input sequence:

Now we don’t have to try to deducing the bit-order from what we think the data stream is displaying, we can build that data into our programming from the beginning. Thank goodness, since I’d never actually seen this display in action before I undertook the task to replace it!

This is about as deep as the research rabbit-hole goes, it seems. We’ve found the datasheet for the EM32 module itself, the OEM-4 module inside it, and the PS035 inside that.

In the next post, we’ll start probing the signals coming from the controller, building a version of the display in software, and testing some theories about how the display operates.

Hanmatek Power Supply

Setting up an Electronics Lab – Tools

Between 10 years working in stage lighting, live video, and theatrical special effects; three moves and two home workbench-overhauls; and my new-this-month position as an Exhibit Engineer at a major Midwest science museum, I’ve planned and kitted-out many electronics workbenches over the years. For those interested in getting involved in hobby or professional electronics work, I’ve compiled the tools I think are most useful when building up a workspace for electronics construction and troubleshooting.

I’m going to specifically focus on tools and support-hardware this time around, and not dive too deep into supplies and consumables, purely to maintain focus. The parts and pieces you need will be wildly different if your specific focus is scratch-building accelerometers vs twitter-connected instant cameras, say. But in the wide and deep pool of ‘working with electronics,’ here are some flotation aids that will keep your head above water most of the time.


As both hobbyists and professionals, we are often looking not for the best tool, but one that’s good enough for the job without breaking the bank. If there’s one tool that I’d recommend getting the ‘good’ versus the ‘good enough’ version, it’s a soldering iron. I thought for years I was just bad at soldering. Nope, just a crappy $25 Radio Shack soldering iron that was doing me no favors.

Not that ‘good’ has to mean ‘super expensive.’ In my home shop and my current shop at work, I used the Hakko 888D, which has proved reliable and durable, even if the interface is a little unintuitive. For less than $100, that’s a darn good iron. The shop at my previous job has a cheapie 3-in-1 soldering/hot-air-rework/power supply station, and for most things that was just fine. They’re such a huge leap above a ‘soldering pencil,’ and they’ll last for years,

Hakko 888D

The trust Hakko 888D. I now have one of these at home and one at work, and they’re a very nice little iron.

Whatever iron you choose, you’ll want some additional tips to go with it. While you could get the pack of every tip imaginable, I find myself using either the medium chisel or the fine-conical %99.9 of the time, so a smaller assortment is probably fine.

As far as solder, while there are good environmental reasons to go with lead-free solder, there’s nothing quite so good to work with as classic Kester rosin-core 60/40, nice and thin. A one-pound reel of that stuff will last most people years. While you could buy a solder-reel stand, I’ve found a 3D-printed design that I really like (credit to Phredie on Thingiverse).

Roll of Solder on 3D Printed Stand

One pound of Kester 60/40 in my favorite 3D printed holder. As busy as we are, I might actually make in through this roll in a year or two.

You’ll also want some flux, either as a paste or in my preferred form as a solder pen. While rosin-core solder has flux built-in, any time you’re doing rework, SMD work, or just taking a little longer to deal with a tricky part, flux makes sure your surfaces are clean and ready to accept the molten solder.

Speaking of keeping things clean, let’s talk about cleaning your soldering iron tip. The sponge and wire-wool cleaner than come with your iron are plenty, if you treat your iron right. More aggressive chemical fluxes like those found in “tip-tinners and cleaner” are meant to remove long-built-up oxidation on your iron tip, and are overkill for routine tip-cleaning. I was taught to dab the iron in the wire-wool between each joint (realistically, between every several joints), and wipe on the sponge before the iron goes back in the stand. That should be all you need.

To remove solder from things other than your iron may take some special tools. De-soldering braid is a great tool – its a woven copper ribbon impregnated with flux, that, when heated against a solder joint, sucks the molten solder up via capilary action. For getting the last little bit of solder out of through-hole pads, a solder-sucker is the tool – find yourself a cheap one, they’re all pretty much the same. At my last job, we purchased a cheap vacuum desoldering station, which was fine, but mostly could have been replaced by solder-wick in 90% of applications. Perhaps a brand-name vacuum desoldering station would have done the job better, but in any case when setting up my shop at the new job, I passed on this tool. For more thoughts on all these tools/techniques, W2AEW has a great video on desoldering if you find yourself in a pinch.

Whether your soldering or desoldering, you’re going to be making some nasty fumes melting all that flux, so get yourself some kind of filtering fan. I’ve got a dirt-cheap Aoyue filter-fan on my home bench, and both a cheap Kotto and an expensive Hakko on my bench at work now, and they’re all about as good as each other, and they all suck (not in the way you want a filter fan to suck). I replaced the fan in my Aoyue with a 120V 4″ Muffin fan (pulled from an closing musical’s fog-distribution system, in my case), and it’s made a world of difference, I highly recommend upgrading. Just be careful, those fans bite.

Hakko FA-400 Fan

Now that’s a big fan! Inherited from a previous museum exhibit.

There are about as many different kinds of work-holding clamps as there are people who solder, but my two favorites are this 3D-printed PCB vise for flat-work and these octopus-style 3rd-hands for other unusual shapes. I’ve used the classic Panavise clamps, and for a shared-shop environment I’d recommend them for their sturdy build quality. But I find them to be a little bit too bulky and their jaws not quite wide enough for the work I find myself doing, so I opt for other solutions in my just-for-me setups. You do you though.

Almost 6″ of jaw space on this 3D printed workholder. You can tell I ran out of grey filament halfway through printing the parts.

Electronic Test and Measurement

The two big items in this category are multimeters and oscilloscopes. Let’s take a look at both of them first before we get into some more specialized tools.

There are lots and lots of good-enough multimeters in the world today, of all kinds of different brands, and they’re pretty much going to all be OK. Rather than try and pick out specific ones from Amazon, here are the features I’d look for if I was looking to add a decent multimeter to my bench today:

  • The basics: AC/DC Voltage, AC/DC Current (up to 10A is useful), resistance (to 0.1Ω and 1 MΩ is nice).
  • Continuity test- this is the most useful setting on a multimeter. Using this setting and touching a wire/component/circuit with the probes will tell you if there’s a low impedance path between the two points; i.e., if they’re connected. Super useful.
  • Auto power-off. Doesn’t seem like much, but it’s real easy to kill batteries without it.
  • 4-digit precision (some cheap meters only give 3)

The other features a meter might have include: temperature measurement, diode-forward-voltage measurement, True RMS AC measurement, frequency (power line), duty-cycle, capacitance, transistor hFE, illumination… the list goes on. I’ve appreciated having a true RMS measurement in tricky AC power situations, and having an easy frequency-check can be handy, but for the rest of these, I’d rather rely on a purpose-made tool like a thermometer, lightmeter, or transistor checker, rather than something built into my multimeter.


I got this meter almost 8 years ago in a moment of need, at a Menards if memory serves, and it’s worked swell ever since.

If you’ve got the cash and are looking for something to last 20 years, the Fluke 117 is a really solid primary meter. Fluke has been the brand name in quality meters for the past lots-of-years – well made, reliable, accurate. Not super cheap, but you do get what you pay for. My current department has standardized on them, and that’s been swell. For most things, we don’t need the $300+ meter (which gives you min/max tracking and microAmp measurement) or the $500 meter (with its fancy clamps and probes). In fact, a basic $40 meter is going to be fine for almost everything you do.

A little aside – why are there no benchtop-multimeters in the super-affordable price range? When you can get a passable, portable multimeter for $20, why are even the cheapie-versions of a benchtop meter still $150? I think there would be a strong market for a $60, benchtop form-factor, ok-ish meter. I have an old Simpson 460-6 at work that I love using, not because it’s the world’s most amazing meter, but just because it’s always there and the form factor is right. How about it, AliExpress?

Simpson 460-6

Now can I get this form factor, with a little adorable LED display, for less than $200?

Moving on to oscilloscopes, I think there are some who would say they aren’t essential for electronics work – after all, if you end up working mostly with digital signals, or analog-voltages that don’t change over time, is it really worth it? I would counter that the oscilloscope is your eyes into the realm of what your electronics are doing, and is a vitally useful tool in many situations. If you’ve never used an oscilloscope, may I once again recommend a video by W2AEW.

Scopes are another arena where you don’t need to break the bank to get something decent enough to use. My first scope was a well-aged BK-Precision 1535A 35Mhz analog scope that a bought from a guy on Craigslist for about $40. For basic electronics work, 20Mhz or so is plenty – you’re most likely going to working at slower speeds (audio to 20Khz, maybe 250kHz for serial or RS485) or much, much higher (HDMI, USB, etc) where a scope really isn’t the right tool in most cases anyway. Or at least, once you’ve progressed to the level where you’re worrying about measuring GHz signals, you’ve likely acquired more specialized tooling along the way.

This old thing is still puttering away on my workbench. Still worked just fine for most things I’d care to do with it.

I think a decent analog scope is a really good place to start if you’ve never used a scope before – better to tackle the fundamentals of the tool before having to learn how to use a particular menu structure as well. The shop at my new job came with a Hitachi V1565 100MHz analog scope with measurement capability that I’ve been very happy with – the ability to add cursors to an analog display to measure voltage, time, or duty cycle is handy. At home I’ve now also got an Owon PDS5022T 25MHz digital scope that was gifted to me – I like the tools having a digital scope provides, but I find it significantly more clunky than either of the classic analog scopes in my life.

Hitachi 1565

The “new” (to me) oscilloscpe I have at work. 100MHz bandwidth is overkill for anything I can think we’ll run into, but you never know…

So, if you’re looking for a bench scope and you’ve never used one before, I’d say start analog. I see on eBay right now you can buy a gently-loved 2-channel analog scope for around $50-60 (plus $40 shipping, those things aren’t light). Not a bad way to go.

Something my accomplice at my old job turned me on to is small, portable oscilloscopes. I don’t have a specific model to recommend, but they can be useful in specific circumstances – not so much to actually interrogate the characteristics of a signal, but more as a signal checker. Do I have AC here, do I have something that looks like RS-485 there, etc? If you do buy one, make sure you get one with an integrated battery (not all do) – getting one that still has to be plugged in makes it far less useful.

There are some more niche electronic tools that I make use of on my bench, but mostly because of my ham radio background. A decent frequency counter is useful in that arena – I’ve got a classic Heathkit IM-2420 that I picked up at a swap-meet, but I’m really intrigued by the new wave of inexpensive benchtop frequency counters that have popped up in the past couple years that claim to do 0.1Hz-2.4GHz for only $70. A signal genetor is also really useful in my work – I built my own around an Si5351 and an Arduino, but you can buy a 0-25Mhz or 0-60Mhz arbitrary function generator for not a lot of cash these days, and I have colleagues who speak highly of both. Since my last job was more lighting-focused, we purchased an Extech digital lightmeter for a specific project – sometime I’d love to get into why that specific meter and the challenges of metering LED sources, but that discussion is too long for this margin to contain.

Some specialized tools for specialized circumstances. A sweep generator, frequency counter, DC power supply, oscilloscope, and homebrew frequency generator.

Electrical Power

A source of consistant, controlled DC power is vital for electronics work, since most projects are going to be some flavor of DC-powered. For basic logic-level type work, the least-expensive option is probably an ATX computer power supply with an ATX breakout board, which will at least provide +3.3, +5, +12 and -12V, which suffices for a lot of Arduino+sensors or Raspberry Pi+breakouts type projects. There are a thousand flavors of those breakout boards, so make sure you find one with the ATX connector type that matches your power supply. There are also screw terminal and terminal lug versions, if you have strong feelings either way.

If your work is less module-oriented and more about building up circuits in a more from-scratch way, a current-limited bench power supply is key. A decent power supply will supply relatively low-ripple DC voltage from 0 to 20 or 30 or 50 volts, at 5 or 10 amps max, commonly. What’s more, you can set a current-limit such that, when your project runs away and tries to turn itself into a pile of smoke, at least it does so more slowly – the power supply will typically fold back its output voltage to keep the output current below the value you specify. Some fancier models also have the option to just cut off current entirely until the power supply is reset.

DC power Supply

Versions of this Yescom power supply are available all over the internet at around the $50 price point.

My current recommended inexpensive bench power supply is the Hanmatek HM305P, for a couple reasons – having a digital display so you can set the output voltage at, say, exactly 5V, is handy. As are the six front-panel preset buttons that allow you to jump to commonly-used voltage/current limit combinations that you specify. That said, at home I have a Yescom power supply with a somewhat higher output current that’s useful for testing RF amplifiers, and its analog controls make it somewhat easier to smoothly vary to the output voltage and see how a circuit/amplifier reacts. If I had to choose only one, I’d get the Hanmatek (or one of its many clones), but an analog-controlled meter is handy for certain situations. (I got by with an Elenco Precision XP-656 500mA 0-30V DC supply as my primary current-limited supply for years.)

Hanmatek Power Supply

The Hanmatek interface (top right) is a little unintuitive, but the manual is decently written. It’s sitting on top of an older tri-voltage power supply.

To connect your power supply to your board, you’re going to need an assortment of wires and connectors. A handful of the typical USB cable types (A-to-Mini, A-to-B, A-to-Micro) is useful, and you probably already have them floating around in your sock drawer. Generic alligator clips are always handy. Mini-grabber style test leads are great for hooking to component leads on a breadboard, though they’re not rated for much current – in those cases, a beefier clip lead is a better choice.

While most projects are going to be DC powered, having enough AC outlets to have all of your test gear plugged in all the time, plus plenty of outlets for temporary plugs, plus a few more, is a tremendous timesaver. You can snag a multi-outlet power strip for relatively cheap these days, but they’re also really easy to find at garage sales, fleamarkets, and swapmeets. The Amazon Basics 6-plug power strips used to be dirt-cheap, like $3 for a two-pack, but as of this writing they’re now $10 for two… a bummer, those used to be a real steal.

If you’re ever in doubt about the functionality of an AC outlet, or if you’re going to be taking your work to a place where AC wiring may be questionable, a cheap outlet tester is useful – it will confirm the presence of AC voltage, whether the hot/neutral are reversed, and other incorrect-wiring hazards. If you just need to confirm whether an AC circuit is hot, a non-contact voltage detector pen is the easiest tool to use – just hold the on-button and place the non-conducting tip near the (potential) AC voltage. If it beeps and lights up, there’s some AC present. Be warned though – the presence of AC-something is not a guarentee of 120 volts or 15 amps or whatever you actually need, just that there’s some fluctuating voltage nearby. Just last week I watched an electrician get mislead by his NCV on a three-phase system – his pen told him all 3 phases had AC, but when he got around to actually sticking his meter probes in the test points, one of the phases was only “33V” to ground (i.e. the system had dropped a phase). You’ve been warned!

Power Tools

While I don’t often use a power drill for actual workbench projects, the ability to stick a screw in a wall or quickly knock a hole in something is nice. I received a cordless Black and Decker 20V drill as a gift years ago, and its been sufficient for my home purposes ever since. Sure, at the point in my career where I was putting 3/8″ lag bolts into 2″ of plywood, the building had standardized on Ryobi impact drivers, which are much stout-er. But the’re also more expensive, and for home-use, I just don’t usually need that much firepower.

My old accomplice turned my on to the virtues of an electric screwdriver. Why would you need an electric screwdriver when you have a high-torque, high speed, large battery drill? Exactly because the electric screwdriver is lightweight, low-speed, and easy to transport – you’re not using it to drive screw into material, you’re using it to take machine screws out of an electrical panel, say. Or install a hundred rack-mount screws. Or take out and reinstall a Euro-rack module 60 times. The light weight and ease-of-use of the screwdriver limits fatigue over long projects like these. Black and Decker makes a fine, inexpensive model.

We’ll get into the virtues of heat shrink tubing some later day when we dive into materials, but an inexpensive heat gun is the appropriate tool for using it. I started with a $10 model from Harbor Frieght which lasted 5 years, and then bought another $10 to replace it. The trouble with all heat guns under $100, it seems, is ergonomics. After you’ve used the gun for a couple minutes and brought the metal tip to a searing-hot temperature, what do you do with it? This Porter-Cable model, with a flat-but you can stand up on your workbench, is the best solution I’ve seen. (Professional models have a flat or angled plate on the back to stand up in just this way.) 

Hand Tools

A few basic hand tools will go a long way in making your workbench serviceable and ready to tackle common challenges – some are worth a little investment, while others are prime fodder for the cheapo Harbor Freight model. And thankfully, there are a number of tools where jumping from the $5 version to the $10 version makes a world of difference, and is worth the Lincoln.

There are lots of different tools to strip insulation off of wire – manual strippers, semi-automated strippers, fully automated stripers, a par of cutting pliers, a knife, your teeth… not that I would recommend all of those. But you can’t really go wrong with a basic set of wire strippers that covers gauges from 10 to 30 AWG. These Paladin wire strippers were our go to at my last job, and they fit the bill just fine. The curved handle takes a little getting used to, but it actually makes them pretty ergonomic, which is nice if you’re splicing a couple hundred bits of wire to LEDs in an afternoon, say. 

A decent set of flush cutters is also worth a minor investment – not more than $7-8 a pair, mind, just don’t get the $3 ones or they’ll fall apart. Flush cutters are the tool of choice for trimming the leads on components, say, but they’re also great for getting a clean end-cut on a piece of wire, or trimming flashing off of 3D-printed models. On the advice of my accomplice at my old job, we’d order 5-packs of Hakko-brand flush cutters regularly, and they served us well. For less critical cuts, a couple pairs of scissors is handy, though for papercraft I prefer single-edge razor blades.

Small pliers are something you can go the inexpensive route on – Harbor Freight or eBay ones would be fine, you’re usually not going to be putting so much force on them that you’re in danger of damaging them. This set of 6 assorted pliers for $20 I ordered for my new workbench has been pretty solid – the extra long, extra thin needle-nose pliers I keep near my 3D printer for pulling ooze off the nozzle right before a print. Having a few heavier duty pliers around is often helpful – just a basic lineman’s pliers for when you need to put some force into the work would be a good place to start.

Long nose pleirs

One of my favorite pairs of pliers – long thin nose, good grip, and $2 at the hardware store.

I must confess – I don’t find the sets of “one small screwdriver handle and 1700 bits” to be terribly practical. They’re great to have around for special projects, but the extra time spent swapping bits back and forth for every project/object/screw is  wearisome. As daily driver small screwdrivers, I much prefer a set of basic jewelers screwdrivers in philips, flat, and hex. This Wera 12-piece set is my go-to recommendation these days, and the carrying-case is nice if you don’t have permanent storage set up yet or if you’re throwing your screwdrivers in a toolbag.

Wera Screwdrivers

Decent screwdrivers that don’t strip themselves instantly, in a nice carrying case too.

A basic 6-in-1 screwdriver suffices for most large screwdriver needs. That link is the cheapest one I could find on Amazon, but honestly, they’re often between $1 and $3 at any hardware store, grab a couple then next time you see one.

It’s amazing how cheap digital calipers have become – less than $20 for a decent 6″ caliper that does decimal inches, fractional inches, and millimeters. The calipers are among the top-five most commonly used tools on my bench, along with the soldering iron, pliers, and screwdrivers. You can measure interior dimensions, exterior dimensions, depth, diameter, all with a precision unmatched by analog means. Get yourself a set, it will change your bench. For larger measurements, a basic tape measure is handy – no need to get a fancy one unless your carpenter-ing regularly.

Digital Calipers

20 years ago, these would have been a multi-hundred dollar item. Now they’re basically disposable.


I wish I had a more in-depth knowledges of adhesives, epoxies, and glues. The properties department at the theater I used to work at maintained an encyclopedic knowledge of which glues were best of which applications, which chemicals were safe for which materials, which drying-times would lead to problems with material interactions… it was stunning. For my general purposes though, there a few basic adhesives that get me through the day more often than not.

Hot Glue is a tremendously versatile material – you can stick most (rough) surfaces together with it, you can build up gussets and supports with it, you mold it to shape a little, and it removes easily from most things except paper. And did you know it comes in black? A decent 100W hot-glue gun is a great “well this just has to hold a little while” solution.

For more permanent fixes, cyanoacrylate glue (also known as CA glue or the brand names Super Glue or Crazy Glue) is a good go-to – it bonds to most things with a slightly-rough surface (so roughing up, say, metal with a file first is a good idea). It hardens in the presence of moisture – atmospheric humidity is enough, but if you put a big glob on something, the outside layer will start to set first and slow the setting process of the inside. Use only a thin layer to reduce this issue – in the right circumstances, the glue will set in a matter of seconds. If you need a little bit more working time or pliability, E6000 Adhesive is a better choice.

Very High Bond double-sided tape (VHB) is an amazing product (well, line of products) from 3M. They give you the versatility of double-stick tape with some crazy adhesive capabilities. 3M’s full catalog of adhesive tapes is worth browsing if you’re into that sort of thing. As a good default, their RP62 foam-tape is strong, slightly spongy (good for bridging irregular surfaces), and relatively inexpensive.

For adhering large sheets of goods together, especially paper products, some kind of spray adhesive is going to be easier to use than a brush-on or dab-on variety. 3M’s Super 77 is the de-facto standard spray adhesive for light- and medium-duty applications – adhering paper to paper for scrapbooking, or laminates to sheet goods. Simply spray Super 77 onto one of the surfaces, wait 60-90 seconds for the adhesive to become slightly tacky, then smoothly lay the second material onto the first. For heavier applications, there’s a High Strength 90 spray adhesive that works much the same.

I’d be remiss if I didn’t mention, a website that generates recommendations if you want to glue this material to that material. Want to stick ceramic to rubber? They’ve got a solution to that, and lots of other combinations as well. Well worth a look.

3D Printing

I know I said I wouldn’t get too far into specific materials or specific arenas of work, but having a 3D printer in your electronics workshop opens up a whole world of mechanical possibilities. Whether its custom enclosures for new projects or quality of life improvements for the shop or project mockups or practical tools, the sky’s the limit of what you can accomplish. Getting started in 3D printing could be a whole series of articles in and of itself, but for the moment let me confine myself to some recommendations of tools to facilitate the practical use of 3D printing on an electronics workbench.

To start, the printer itself. I don’t have any experience with SLA 3D printing, only the more traditional FDM method. An FDM 3D printer is essentially a fancy robotic hot-glue gun on rails, that moves precisely around a 3D space squirting out hot plastic as it goes, which sets into shape as it rapidly cools down. This is a relatively speedy way of printing an object, but the spatial resolution of the resulting object is limited by the resolution of both the stepper motors that push the print-nozzing around and the diameter of the print nozzle. Still, with a stock 0.4mm nozzle and a basic machine, some really beautiful things are possible.

Wall Thermostat Tag

How do YOU control your hot-end?

If I were to recommend a first FDM 3D printer to someone today, it would be the Original Prusa MINI. Josef Prusa was one of the original movers and shakers when the hobbyist 3D printer train was getting rolling in early 2010s, and his i3 model is perhaps the most popular 3D printer in the world. With a reputation for a great product and great customer service, the release of a printer at that key $350 price point that’s become so popular, with mesh bed leveling, a heated bed with removable build-sheets, ethernet connectivity with WiFi upgrade possibilities, an option filament run-out sensor… I’m very excited for this thing. It’s currently on pre-order for $350 US to start shipping around the end of the year, and I think it’s going to be a slam dunk. When I think that i paid about that much for my Monoprice Maker Select V2.1 only 3 years ago, it’s amazing to think how far the technology has come.

3D Printer

This printer took a few mods to make the frame rock-solid. Amazing what 3 years progress looks like.

Of course, all of the specific nozzles, filaments, and accessories you need will be specific to your printer and your projects. But I can recommend a couple of tools that will be useful to all FDM 3D-printing setups, the first being a set of 3D printing spatulas. Most printers ship with a putty knife as their print-removal-tool, which is an excellent way to gouge a hole in your print surface (or your hand!). Since receiving a set of these spatulas as a present for Christmas last year, they’ve easily become the tool I keep closest to the printer.

3D Printing Spatulas

These were definitely sitting on a shelf somewhere as palette knives and someone thought “you know what we could sell those as? 3D printing spatulas!” But they work, so who cares.

Second, while there are lots of methods of getting your 3D print to stick to the print bed, keeping the bed itself clean of oils and debris goes a long way toward success. I keep a bottle of high-strength isopropyl alcohol and some lint-free clothes nearby to wipe down the bed between every few prints, just to make sure the residual oils from printing and from my hands don’t cause premature liftoff from the print bed.


In this digital age, MS Paint is just as practical a tool as a paintbrush. So let’s not leave out the digital tools that we use to make, track, distribute, and record projects on the workbench.

For 2D drafting, my two primary tools are AutoCAD and Vectorworks. AutoCAD (made by AutoDesk) is an incredibly powerful CAD program, and it’s been around forever. Want to model a bracket, or a whole airplane, or design a building, or pocket watch? AutoCAD can do it. It does have a fairly-steep learning curve – there are folks who make entire careers out of just working in AutoCAD – but it gives you a lot of power for your trouble. Vectorworks is a less-commonly-used program that I became very familiar with in my years as a stage lighting technician; due to its excellent stage-lighting plugins, it’s the de-facto standard for theater lighting. And where AutoCAD focuses on building a “model” and having you derive drawings from that model, Vectorworks focuses on the drawing itself as the thing to be made. It might seem like a semantic difference, but the way that those philosophies influence the workflow of the two programs means that Vectorworks is often my choice for creating 2D draftings.

For 3D drafting, my go-to software is Fusion360, also from AutoDesk. Fusion is a timeline-centric, parametric drafting program, which allows you to go ‘back in time’ to an earlier moment of a design, make changes, and see them ripple through to the current version of the design. It’s a very powerful program, though not without its own learning curve. For someone just diving into 3D modeling for the first time, I’d recommend starting with something like Tinkercad, a cloud-based modelling program that centers around adding and subtracting primitive objects from each other to build up a more complicated design. I’ve also had friends work in SketchUp, which tries to blend Fusion’s 2D sketch capabilities with the ease of Tinkercad. Unfortunately, SketchUp seems to have trouble successfully exporting STL files for printing, so I can’t recommend it as a strong starting point.

Fusion 360 Screenshot

Fusion is a very powerful, very worth-learning program.

Once you have your 3D model and you’re ready to print it, you’ll need a slicer program to turn the model into a series of step-by-step instructions that the printer can actually follow. (“Move to such-and-such coordinates in so-many seconds while extruding this-amount of plastic“. Repeat x10000). I personally use Cura, now from Ultimaker. It’s straightforward to use, and has all the options and customizability I’ve found a need for. I know lots of folks who have good opinions about the open source Slic3r project as well.

Programming and text editing may or may not be a part of your electronics hobby, but if they are, having simple straightforward tools is a good way to get more productivity out of your text-based time. Of course for programming Arduinos, the Arduino IDE is a perfectly good place to start. It’s not fully featured in an respect, but it just works, you can write code in it and plonk it on an Arduino, and that’s all most people care about. I use Sublime Text as my main text editor and sometimes basic dev environment (when writing things in Love2D, for example). 

For projects that are just too detailed to lay out by hand, I design circuit boards in AutoDesk’s Eagle software, though there are some who would say I’m a heathen for not using the open source KiCad. To be honest, I don’t have strong feelings about either software either way – Eagle was just the first one I used and I’ve become used to its workflow and design choices, but I know there are die-hards on both sides of this river. Regardless, to live in an age where a maker has multiple, quality options for free PCB design software is amazing.

DMX Circuit Board

I would never in a million years be able to achieve this level of miniaturization with a hand-fabricated board.

Of course, once you’ve designed a circuit board, you’re going to need to make it, somehow. While they’re not software per-say, the growth of PCB shopping cart websites over the past few years has really opened up what’s possible for the solo electronics workshop. No more sweating with getting tiny wires soldered to tiny chips to break them out to veroboard; you can just spin a PCB with the proper footprint, or indeed the whole circuit. Any of these services will let you upload your circuit board design, and for a very modest fee spin you up 3 or 5 or 500 copies. OSHPark really started the whole small-batch-PCB movement, and their service has always been great, reliable, and high quality. I’ve also used JLCPCB for somewhat larger runs. If you’re interested in looking at many, many options, PCBShopper is an aggregator that lets you compare prices, lead times, and options across almost two dozen shopping cart-style manufacturers.


Just because you may not have a giant 5-axis robot in your workshop doesn’t mean you shouldn’t take safety seriously. Whether your workshop is in your home, an outside shop, or your workplace, a few basic safety precautions could mean the difference between peaceful Thursday and a trip to the ER.

Smoke and carbon monoxide detectors should be present in several places in your home or office already, but having one in the workshop is a good idea, especially if you have any hot-tools (soldering iron, heat gun, 3D printer). They’re so inexpensive and easy to install, it’s a no-brainer to pick one up. A fire extinguisher should also be on your list – and if you ever have the opportunity to get a little training on how to properly use one, it’s well worth it. Make sure to mount your fire extinguisher where you could actually get to it, if the things that are most likely to start a fire, did.

Fire extinguisher

I put my fire extinguisher right by the door to my workshop, so I can grab it on the way in, or on the way out.

While we’re thinking about fire, consider whether your workshop needs a flammables cabinet. If you’re storing more than a few things of paint, spray paint, spray adhesives, solvents, cleaners, etc, it’s worth thinking about what would happen if they were to catch a little on fire. It’s not usually worth buying on online – the shipping is killer- but cabinets pop up on Craigslist, auctions, and industrial surplus all the time. Go Industry Dove Bid is a good online collector of industrial surplus auctions, but be sure to check out your local city/state surplus resources as well.

Finally, safety glasses. Just wear them, even when you think you don’t have to. About 4 years ago, while soldering “just one more joint” on a PCB before going to bed, a piece of hot solder popped up and got me in the lower-left eyelid. A quarter-inch higher and it would have been right in my eye, with who knows what consequences. I’m not always perfect about this myself, but I do keep a pair of safety glasses right on my workbench to remind myself that if I want to take a risk, it’s my own damn fault. Get a pair of glasses that are comfortable so you’re more likely to wear them. 


Resistor Bins

No such thing as too organized.

I’ve come to realize something over the past 10 years – the most volume I’m willing to rummage through for a tool, part, or piece is about 500 cubic inches, or a around 10 liters. Any more volume than that, especially for small parts, and there’s just too many potential places where a small object can hide. So standardizing on a storage bin that’s slightly smaller than this makes good sense. At home, I use 6-Quart Bella bins from Menards, while at work I use 6-Quart Sterilite bins. Once a project or set of components or tools overflows one of these bins, there’s probably enough diversity in goods to split it up into two separate bins anyway – i just recently split the Microcontrollers bin into Arduinos and Non-Arduino Microcontrollers, for example. Now both species are easier to find.

Storage Bins

So many pretty bins, all in a row.

I’ve always loved a good whiteboard (I just snagged another 18″x24″ one for my office), but I recently stumbled upon these ultra-fine tip whiteboard markers, which I just absolutely love. They allow you to squeeze so much actual detail and small size into a whiteboard doodling project. Not for presenting to a group, mind, just for working through projects on your own or with a partner. (I also 3D printed a cup for them for my kitchen whiteboard calendar, more on that in a future post I think.)

Wall Pen Cup

I’m a strong believer in the power of labeling to make things just so, and a labelmaker is a really easy way to help keep things organized. The Brother PTD600 has been a nice blend between portability and computer control – you get most of the functionality just using it handheld, or you can hook it up to Brother’s software on your computer to make more complicated layouts, batch prints, etc. The sound department at the theater I used to work at had a Rhino BMP21-Plus, which was really awesome at making self-laminating labels to label cables – with the amount of work that went into cable arrangement and maintenance in that place, the self-laminating labels were a godsend. The tape’s a little pricey, as is the labeller, so if you’re not doing a lot of patch panels, say, I would stick with the Brother and the TZe line of tapes.


Decent task lighting makes a world of difference – you’ll find you’re suddenly better at soldering, more deft at assembly, swifter to catch errors and notice mistakes. No sense working in the dark if you don’t have to.

I’ve done a number of lighting setups in my home workshops over time. Right now I have three 24″ fluorescent fixtures overhead that were remaindered from a theatre production ages ago (in addition to a basic 100W ceiling light). I’ve also got a couple of clip lights with 100W LED bulbs closer to my actual workbench surface to price more focused task lighting, and a cheap gooseneck light from IKEA sitting on the work surface for when I need really targeted illumination. While I haven’t re-installed it since I moved into a new home workshop a few months ago, adding under-shelf lights to my home shelving setup made a big difference in being able to see and find components on the shelves, as well as adding some cheery glow to the workstation. My workshop at work has lots of overhead fluorescent light, and I added a positionable jointed lamp for some more focused lighting. 

Your Own Shop

If you’re still reading this 6500 words later, you might thinking – “Holy crap, that’s a lot of stuff, I’ll never be able to have my own electronics workbench”. But keep in mind – this is the setup and tools that work for me, with what I want to do, that I’ve built up over a decade of working professionally and as a hobbyist in this arena. Would you look at a professional auto mechanic rebuilding an engine and say “Wow, I’ll never open my hood again?” It’s all a matter of starting somewhere.


Two apartments and many years ago, this is what my “workbench” looked like. And it was still a BLAST.

The easiest way to pick a project is to find a project you want to accomplish and work toward making it happen. Maybe it’s monitoring to see whether your garage door is open or closed. Or what the weather’s going to be tomorrow. Maybe your dog needs some entertainment, or you need a new sparkling light over the crib, or the you have an itch to build a radio or a tesla coil or who knows what. Once you find a thing you’re excited about building, that will guide you as to which tools to find first, which will lead you to more things you can do with those tools, which will lead to more tools… and so on. 

And most importantly – have fun.

Special Thanks

I wouldn’t have been aware of so many of these tools, ideas, and possibilities without a lot of excellent colleagues and friends. Thank you especially to Kenneth, Palmer, Alec, Joe, Mike, Jabin, Lee, Travis, Chris, and all the other excellent technicians who continue to be an inspiration for excellent technical work.

Also, just in the interest of disclosure: most of the Amazon links above are affiliate links. Purchasing through them provides a small amount of compensation to me at no cost to the buyer.

Closet Door Locker

Yesterday I install a new closet door in our front entrance hall, and discovered a problem which I then solved with 3D Printing. The door is a standard bi-fold type, with pins in the top and bottom of one side for rotation, a central vertical hinge, and a track along the top to keep the far side in alignment.


The problem was – with the volume of coats we need to survive a the winter on the ice planet Hoth (Chicago) and the positioning of the hanger rail, the coats push the door out and prevent it from staying fulling closed. Given that this is immediately adjacent to the front door, not an ideal solution at all.

There are lots of types of locks/clasps/magnets designed to solve this problem, but the one I chose to emulated is this over-the-door babyproofing product. It’s essentially a c-channel of plastic that slides over the middle-hinge when the door is closed, to prevent it from swinging open. Genius.

I created my own variant in Fusion360, thinking about how to make the design rigid, printable, and aesthetically pleasing. I added ridges along the sides to increase its lateral strength, and little pull-tabs to make it easier to grip. I trussed-out the top to give it some additional strength and reduce weight. Here’s how it ended up after about an hour of drafting:

Printing took a little over 10 hours, and the final result works great. I selected a blue-green PLA+ for ease of printing and aesthetic considerations:

Thanks 3D printing!

ETC Console Output Counts

What follows is a list of output-counts for ETC Eos Family consoles. Because I’m always needing to reference this information, and I want to be lazy when I need to find it. So, without further ado, here’s the current output capacity for different ETC consoles, as of July 24, 2019:

ConsoleVariantBase Output CountUnlocked Output CountLegacy Consoles Upgraded to 2.6 Software
Eos TiDisplayPort4096
(8 * 512)
(48 * 512)
Eos Ti DisplayPort at 5K or higher now @ 24,576
Eos TiDVI4096
(8 * 512)
(32 * 512)
Eos Ti DVI at 5K or higher now @ 12,228*
Eos RPU3DisplayPort4096
(8 * 512)
(48 * 512)
Eos RPU3DVI4096
(8 * 512)
(24 * 512)
Eos Classic  4096
(8 * 512)
(8 * 512)
Eos Classic at 5K or higher now @ 8192
Eos Classic RPU  4096
(8 * 512)
(8 * 512)
Eos Classic RPU at 5K or higher now @ 8192
(8 * 512)
(48 * 512)
Gio Displayport at 5K or higher now @ 24,576
(8 * 512)
(24 * 512)
Gio DVI at 5K or higher now @ 12,228
Gio @5 4096
(8 * 512)
(48 * 512)
@5 at 5K or higher now @ 24,576
Ion XE 2048
(2* 512)
(24 * 512)
IonWindows 71024
(2 * 512)
(12 * 512)
Ion Win 7 at 1536 or higher now @ 6144
(2 * 512)
(6 * 512)
 Ion XP at 1536 or higher now @ 3072
Ion RPUWindows 72048
(2* 512)
(12 * 512)
Ion RPUXP2048
(2* 512)
(6 * 512)
ETCnomad 512 6144
(12 * 512)
Nomad 256 now @ 512; Nomad 1024 or higher now @ 6144
ETCnomad Puck4 USB512 6144
(12 * 512)
Nomad Puck 256 (3 USB) now @ 512; Nomad Puck 1024 (4 USB) or higher now @ 6144
ETCnomad Puck3 USB5122048
(2* 512)
Nomad Puck 256 (4 USB) now @ 512; Nomad Puck 1024 (4 USB) or higher now @ 2048
Element 2 1024 (2 * 512)6144
(12 * 512)
Element 1024 (2 * 512)  
ETC Nomad “256 1024 (2 * 512)  

*The listed Eos Ti DVI count for previously-smaller-output-count consoles doesn’t match the new Unlocked output count. This may be a typo by ETC.

This info comes from: the EOS Software 2.6 Release Note, the Upgrading Eos Family Output Counts page, the Element Tech Specs page, the Element 2 Tech Specs page, the Ion Xe Tech Specs page. As always, information from ETC will always be more accurate than the blog of some guy in the Midwest – this is meant to be a helpful reference, not a definitive source.

The legacy consoles section indicates the new output counts for consoles that were available before Eos software version 2.6, when consoles were available for purchase with much more granular output counts. The 2.6 software upgrade standardized all consoles to either a Base model or Unlocked, with all consoles moving to the next higher output count available (e.g. no one lost output capability with this upgrade).

Some background, and an explanation of why output counts aren’t round numbers: ETC’s line of Eos-family lighting control consoles can be purchased with different numbers of parameter outputs. In an older way of thinking of things, one might have had a limited number of universes. As I’ve featured in my post about lighting control protocols, each universe contains 512 “slots” of information, and individual devices (dimmers, intelligent lights, other controllers) can be told which slots to listen to by giving each device an “address” (or range of addresses).

The key difference is that now, with lighting data being largely distributed over a network and only turned back into ‘hard’ serial DMX near its endpoint, limiting a controller’s output to only 2 or 6 or 24 physical universes would be a little unnecessarily constraining. Instead, the output count is how many total DMX slots one can control, spread across as many universes as the user desires. So, a basic Nomad, for example, could control all 512 slots in a single DMX universe, or a single address in each of 512 universes, or anything in between. Only addresses which are patched count toward the total output count.

For more info on addresses and parameters, see ETC’s article: Addresses and Parameters in Eos Family Consoles

Arduino DMX ‘Light Board’, Mini Moving Light Hanging Hardware

Over the past week, I got to the point with the mini moving light that I needed some way to consistently pump DMX into my prototypes to test their functionality. Thankfully, the first set of PCBs I built for this project function as both DMX receivers and transmitters, so whipping together a basic DMX controller only took about 20 minutes.

So here it is: my tiny DMX controlled “light board”:

Not much to look at, really. It’s just the DMX Control Shield I build earlier, with its Arduino Pro Mini, and 3 potentiometers from the junk box. The ends of each pot are tied to +5V and ground, and the wipers are tied to three analog pins.

Originally, I had the Arduino just reading the straight value from the analog pins, mapping those 10-bit (0 to 1023) values from the ADC to 8 bit (0 to 255) values suitable for DMX, and shoving those out as DMX addresses 1,2, and 3 as fast as possible. But I found that some inconsistency in the analog readings caused the servos and LED to twitch and flicker noticeably. So I modified the code to read the values from the pots every 20 milliseconds and average the last 10 readings when outputting. The output values calmed right down.

The result is a reasonably stable controller, and plenty to test the mini moving-light with:

I also made some specific improvements to the physical design of the light, including:

  • Lengthening the body to accommodate the Carclo optic and heatsink
  • Adding vents to the body for heat-removal
  • Including some new wire-routing holes in the base and widening others for improved cable routing.

I also designed and printed some (really adorable) 1″ triangle truss and some hanging brackets to mount this thing on. Here’s the moment from my Sunday night livestream where I hung the light on its truss for the first time:

Just today, I got in another couple orders from DigiKey, and my latest batch of PCBs from JLCPCB should arrive tomorrow. The notable improvements to the PCB and parts include:

  • Separating the Pan and Tilt servo pads (doh!)
  • Switching to a stout-er 5V regulator
    • I also ordered a few VX7805-1000’s to play with. They’re a self-contained, fixed-output buck converter that’s meant to be a drop-in replacement for a 7805 linear regulator. Neat part if it works, and not horribly expensive.
  • Switching to an inductor spec’d for 1A forward current instead of 500mA.
  • Switching to a schottky diode rated for 30V instead of 20V.

Assuming this assembly goes well, I hope to build two or three of this version (which I’m calling version 0.4) and set them up for a little DMX-controlled dance party. Here’s hoping!

DMX Mini Moving Light First Assembly – Live Stream

With the shell 3D-printed and the PCB assembled, I went ahead and put together my first “completed” mini-moving light, live on camera:

It went fairly well – everything mostly worked and nothing caught fire!

There are a few mechanical and electrical takeaways for the next version, including:

  • Mechanical:
    • Ennlarge the hole for LED wires in the lower case
    • Make a brief instruction manual for myself of what needs to be assembled/installed/solder in what order
    • Hole for program/enable switch access
    • Fix tolerances on the tilt-servo/yoke interface
    • Lengthen the body to accommodate a heatsink for the LED star
    • Figure out mounting/hanging hardware
  • Electrical:
    • Increase the spacing between Pan and Tilt Servo pads
    • Order higher-current 5V regulator (1.5A 7805)
    • Select a new inductor for up to 1A of current
    • Select a new schottky diode for up to 24V
    • Combine the transmit/receive control lines onto a single pin of the Arduino.

But all in all, for a first assembly, even tripping over a couple of silly mistakes on my part, things went pretty well. Onward to V0.4.

DMX Mini Moving Light Shield V0.3

As I hinted to in my original post about the Arduino Pro Mini DMX Shield, and then talked some about in my PCB Assembly Livestream, the latest version of my DMX shield is geared toward driving in miniature moving light. This means that, in addition to being able to receive DMX, the Arduino driving the device will need to be able to drive a couple of servos and dim a relatively high power LED. There are many way of skinning both of those cats, so let’s look at the solutions that are present in V0.3 of the DMX shield.

Servo Control

Of LED dimming and Servo control, the latter is the easier problem to solve. While there are dedicated servo-driving IC’s, and modules, almost any microcontroller, including the ATMEGA238/Arduino can control a hobby servo in a straightforward way using minimal additional hardware.

A typical hobby servo needs only three wires running to it – +5 for power, Ground, and a control line. The control line carries the position data for the servo in the form of pulse width modulation. The servo expects to see a pulse every 20 milliseconds. A pulse of 1.5 ms corresponds to the center (90°) position of the servo. A 1 ms pulse rotates all the way in one direction (0°) and a 2 ms pulse rotates fully the other direction (180°). There is a standard Arduino Servo Library that translates degrees inputted into the appropriate duration Servo pulses.

Image Credit: Wikimedia Member Hforesti, CC-SA-4.0

The only additional hardware present on the V0.3 board for Servo control is, therefore, a bulkier 5V regulator. The 5V regulator on an Arduino Pro Mini isn’t particularly stout to begin with, and I’ve had issues on previous projects with “off brand” Pro Minis having even less 5V oomph than that. So there’s a pair of DC input pads and a TO-220 packaged 7805 to provide a healthy amount of current for the servos.

LED Dimming

The LED dimming half of this project has a wider solution space than servo control. The typical solution is MOSFET dimming. A FET is switched on and off rapidly, with a variable duty cycle to control brightness. This is the solution that commercial DMX LED decoders use, with a bank of 3A-5A fets, one per driven channel. It’s simple and inexpensive.

The problem is heat. MOSFETS with super-low on-DC resistances are expensive, and those with higher DC resistances create more heat. There’s always a balance being struck between cost and current carrying capacity. Which is why most commercial DMX led dimmers sit in a sweet spot between 3A and 5A. And all of them come in metal cases, sometimes mounted to large heatsinks, to help with heat dissipation. Less than ideal for what is ultimately meant to be a 3D-printed moving light made of thermoplastic.

The other problem is overcurrent regulation. For typical, inexpensive 3A per channel DMX LED driver, there’s nothing to protect the FETs if you load up a channel with, say, 5A of load, there’s nothing in the drivers to prevent the FETs heating up to their failure point. Or worse. See, for example, this example from a local theater:

After some investigation, it turned out that there was a wiring error causing a dead-short across one of the channels. Which subsequently burst into flames. No kidding. The Stage Manager reported seeing a cloud of smoke roll out of the vom, which it turned out was discharge from the fire extinguisher the crew was using. Yikes!

With a controlled environment and a defined load, an overcurrent load is slightly less of a concern, but it seemed like there must be a more elegant solution to both the heat and overcurrent issues.

The solution I’m currently trying is the the AL8860 Buck LED Driver. It is essentially a DC-DC step-down converter which derives the average current through its load from a SET resistor between a couple of its pins. It has an input voltage from 4.5V to 40V, and in TSOT-25 form factor a maximum current of 1A. A TTL PWM signal applied to its CTRL pin brings the average current down from the maximum SET current to between 0 and 100% of maximum, depending on duty cycle.

While the IC itself ultimately uses an NDMOS FET to do its switching with a relatively high on-state resistance (200 mOhm), its incorporation of current management and a step-down converter directly into the IC makes it an attractive option. And for the form factors I’m looking at, I’m not likely to be pushing more than 1A through an LED star anyway.

The AL8860 requires a few external components as a buck converter would – an inductor and a schottky diode – as well as a bypass cap and the SET resistor(s). These altogether take up about as much PCB space as a decently sized FET switch would, let a long the voltage conversation IC’s that would allow this to run on a variable voltage.

The portion of the PCB directly responsibly for 1A LED dimming. Approximately 8mm x 8mm. The two large thru holes directly below this are points to solder leads from the LED star directly.


I made the bold choice of testing this IC and hardware on a livestream recently. But not before an unscucessful attempt test attempt.

In an attempt to validate this IC idea before committing to it, I purchased a handful of AL8860s, schottky diodes, 0.1 Ohm resistors, and inductors, and tried to piece together this idea on a piece of copper-clad. That did not, in short, go well. Without proper pads, I couldn’t get the IC to stay in place well enough to solder magnet-wire to it. Even after I super-glued it down, the heat from my soldering iron weakened the super glue and caused it to come unstuck. And release superglue fumes. Fun!

So I pulled the trigger on ordering a batch of the V0.3 PCB’s, this time from JLCPCB. But in my rush, I didn’t run a final Design Rule Check, and the pads for my Pan and Tilt servos overlap. Ah well, this was mostly to validate the LED dimming circuit.

And validate it did! Check out this gif from my testing session:

Now that’s some light! The arduino was just running a simple ramp-up/ramp-down for validation.

The LEDs are from LEDSupply, a vendor on the east coast that I haven’t used before, but stumbled upon while looking for LED options. They happen to be having a closeout sale on some Luxeon R 3-LED stars, which seemed like a good option for something I might smoke or blow up. The LEDs themselves are Luxeon LXA7-PW40s. And with the appropriate Carclo optic, the beam width is fairly narrow. The heatsink is just something from the junk bin.

At 1000mA forward current (which LEDSupply recommends as the maximum allowed current), they emit around 975 lumens total, around what a 75W PAR16 lamp emits. Even testing at 500mA as I was, it’s a punchy little package!

Next Steps

There’s some CAD time in my future. I’ll need to whip up a case to hold the PCB and accommodate a pan servo. I think the arm and body components I will be able to mostly re-use from my previous design, possibly with a little extra room in the head for a proper heatsink.

The previous tiny moving-light design

At some point, I’ll have to re-order PCB’s with the errors corrected, especially the overlapping servo-control pads. I may also want to rethink the mounting hole locations, and possibly bring the DC and DMX inputs out onto their own little tabs to solder connectors onto. But first, I think it will be satisfying to bring this version of the LED to life.

DMX Mini Mover Shield PCB Assembly Stream

Last night, as I started to assemble V0.3 of my DMX Mini-Mover Shield, I thought it might be fun to switch on my webcam and stream the assembly live to the World Wide Web. What follows is about 80 minutes of unstructured benchwork, chatting about DMX, sACN, and circuitry, and a first test of the new LED dimming circuit. Will it light up, or will it go boom? Watch the video to find out:

Arduino Pro Mini DMX Shield


In my dayjob as the lighting supervisor of a midsize regional theater, we get to play with all kinds of fancy (and expensive) lighting equipment – moving lights, high-power color changing LED units, ultra-compact wireless dimmers, and so on. But it’s also fun to build inexpensive, maker-size versions of of this equipment, and it can be done on a shoestring budget.

About a year ago, I built a couple versions of tiny moving lights – one directly from a design from Thingiverse, the other of my own making. The end result was super cute!

The thing with this tiny light compared to real moving lights was… I cheated a bit. The light itself only contains the servos and LED chip itself, while the controller, LED driver and ballast were all external. The full setup took up almost 3 times the volume of the individual light:

Not only did I cheat on size, I cheated on control a bit too. The unit has a number of ‘test’ modes that run simple movement and color patterns, but there was no means of controlling the light externally. While there are It was basically a fancy keychain toy. And there are DMX Shields in the Arduino Uno form factor, they themselves would have outsized the lights by another 200%. It was all getting too bulky to be reasonable.

But after many months away from this project, I’ve been devoting some time to scaling down both the dimming and DMX control sides of the circuitry. The result is a shield for an Arduino Pro Mini.


As described in my previous write-up of contemporary lighting control protocols, the core standard for modern stage and event lighting is DMX, or properly, ANSI E1.11 DMX 512-A Digital Multiplex. In short, DMX is a serial protocol and physical spec that caries up to 512 one-byte values over each individual cable, usually with 5-pin DMX connectors. One set of 512 values is termed a “universe,” and to carry additional values, additional cables carrying different universes of information may be added.

More formally, DMX is a 250 kbps serial protocol transmitted over a 2-wire bus following RS-485 standards. The ESTA standard standards also dictate standardized connectors (XLR5 for temporary installations, RJ45 for permanent infrastructure), network topologies, impedances, terminations, and so on. The standard is pretty readable, if you enjoy that sort of thing.

DMX was developed in the late 80’s/early 90’s as a replacement for systems in which lighting equipment was controlled via analog control voltages, meaning each parameter (each individual dimmer, say) required one wire. A rack of 96 dimmers would have 100+ pin wiring harness attached to it, each with an analog voltage specifying level. With the introduction and adoption of DMX, all that was replaced with a single 3-conductor cable. All modern stage lighting controllers speak DMX, although most rely on transporting universes of DMX over Ethernet and using ‘DMX Nodes’ to turn that digital data back into ‘hard’ DMX close to the fixtures being controlled.

Circuit Components

There is really only on piece of hardware required to add to an Arduino-compatible design to allow it to send/receive DMX: an RS485 transceiver chip. There are many of these on the market, the common ones being the MAX485 and the SN75176.

These take a single-ended input and turn it into a balanced output or, conversely, receive a differential RS485-compatible input and convert it to a single ended signal to a microcontroller. There are two control pins which determine whether the chip is a receiver or a driver. The control circuitry is essentially the same at both the transmitting and receiving end:

A more sophisticated/robust approach would also incorporate an optoisolator to prevent the processor from being damaged by faults on the signal side. There are some good guides on the interwebs on setting up optoisolation with DMX for an Arduino ( has a good write up of their isolated DMX shield), but for the sake of quick progress I’m making this a future goal.

Circuit Layout and PCB Manufacture

The circuit is ultimately very simple – a couple headers, some resistors, a MAX485 IC, and some pads to connect the DMX connectors to. And a switch – the DMX library I’m using abuses the Arduino’s built-in Serial library for some of its functionality, which means it has to use pins D0 and D1. Which means you can’t reprogram the Arduino with DMX coming in. The DPDT switch just removes the connection between the DMX connectors and pins D0 and D1 of the Arduino to allow for programming.

Mostly for my own reference, the connections between a standard XLR3 or XLR5 connector and the Max485 pin are:

Net Name XLR Connector Pin Max485 Pin
GND 1 5
Data – 2 7
Data + 3 6

Here’s what draft one of version 0.1 looked like when it came back from OSHPark and following assembly

All the passives are 0603 and the max485 is an SOIC, both of which are pretty easy to solder by hand. The SMD switches are adorable! They’re these little guys from C&K.

The major flaw with version 0.1 is: one you’ve attached headers, where do you attach anything else?? So version 0.2 added an additional row of thru-hole pads, cleaned up some labeling, and added some mounting holes for M2 screws:

And once its all assembled, it looks something like this:


I’ve been making use of the Conceptinetics DMX library, which I’ve found to be both functional and stable. I haven’t yet experimented with the RDM capabilities of that library.

The library is very easy to use, and its usage is described well on the Conceptinetics Documentation page. Essentially, one defines a DMX_Slave object, which has enable(), setStartAddress(), and getChannelValue() methods.

For example, once the object is set up and addressed, a loop() with the single command analogWrite(LED_PIN, getChannelValue(1)); will dim an LED attached to pin 9 dim in response to incoming DMX. Easy as pi.


So, what can one do with an Arduino Pro Mini that can receive DMX? Well…

You can make a DMX level monitor, a DMX controlled LED source. And really, anything else you can think of to do with an Arduino – drive servos, WS2812s, solenoids, relays…

The shield can also transmit DMX, though I haven’t thoroughly tested this yet. But it’s possible to make a miniature DMX controller, itty bitty light board, or testing tool. Or wire up some interesting input devices and make an interesting lighting controller.

What’s Next

The shield has been a useful proving ground for the Conceptinetics DMX library (though we’ve used it onstage before), as well as for OSHPark’s manufacturing tolerances. I wasn’t sure that having holes as close to the edge of the PCB as both V0.1 and V0.2 have would be manufacturable, but they came back no problem.

This all started for me with a miniature moving light project, and while that’s not quite ready for a write-up, I’ll just leave V0.3 of the DMX shield here. Not without errors/improvements to be made, but I’m excited to try out some new LED dimming tech: