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.

Testing

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

Introduction

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.

DMX

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 (Mathertel.de 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:

Programming

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.

Usage

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:

3D Printing in the Home Workshop

With the bulk of the shelving and organization overhaul complete as of last week, I’ve spent the last week starting to personalize my home workshop space, mostly using my 3D Printer. This is definitely a situation of “when your favorite tool is a hammer, everything looks like a nail.” And the 3D printer is an awfully nice hammer…

There are some things that 3D printed plastic parts are perfect for, including:

  • Brackets to attach/connect unusual shapes
  • Containers/guides for specific materials and tools
  • Stands and supports for lightweight goods

But of course, there are some properties that 3D printed thermoplastics are always going to be underachievers in, like:

  • Brute strength (compared to metal or wood)
  • Tiny mechanical details (like screw threading)
  • Heat resistance

In my mind, an ideal setup picks and chooses the materials that are right for each job. There’s not much point in printing, say, a 24″ wide shelf when a wooden one with be stronger, cheaper, and easier to make or buy. Conversely, welding a microphone stand together out of metal would be a nightmare, where it’s easy to print an existing plastic design that will hold up just fine.

The thrust of this is that, with the ELFA shelving (wood and metal) providing the backbone of my setup, there’s lots of space to fill in the operational edges with 3D printing. I can’t possibly cover every print, but in no particular order, here are the new additions to the setup, and some most-useful oldies:

ELFA Corner Bumpers

I designed and printed these the same day I finished the shelving install, after my partner nearly beaned herself on the corner of a shelf by the doorway as she was getting up. They’re a tight enough fit that they stay out without adhesive or fasteners. The design is now on Thingiverse.

ELFA Cable Guides

With the number of things that plug into AC power on my bench, I figured cable management would be useful. I started by putting together an ELFA Shelf Hook Profile, which can be used as a basis for anything that hooks into the ELFA vertical standards. I then added an L-hook shape to one side of the profile, which captures any cable that are hooked into it before the piece is installed. This is the result.

ELFA/2020 Bracket

I’m trying out using a piece of 2020 extruded aluminum as a generic mounting rail for some desk equipment, including the camera arm below. Maybe I’m being precious because the shelving is still new, but I couldn’t bring myself to put holes into the front of the shelves to mount this rail in place. I designed and printed these brackets, which are a tight fit to both the front of an ELFA solid shelf and the 2020 piece, and further secure to the 2020 with a screw and a hammer nut. A small piece of blue-tak can be fitted to the slots on the underside to prevent the bracket from sliding off.

This will probably need a second draft, as I realized after installation that they don’t leave room for the LED lighting I intend to install under each shelf.

Lighting PSU Wall-Standoffs

I’ll get into the lighting for the room more once all the parts arrive on the slow boat and I can get it all installed. In the meantime, I’m starting by mounting the 30A, 12V PSU. The positioning of the vertical standards on my wall didn’t leave an obvious place to mount the PSU, but the unit does have four M4 threaded holes on the sides. I designed and printed these mounts to accept up to three drywall screws each, with a slot and countersink for an M4 screw.

Articulating Camera Arm

Having a semi-permanent camera on my desk has been useful for project documentation. This is an assembly of two prints by other makers – RaffoSan’s Universal Camera Mount and Felwats’ C920 Adapter. The adapter actually fully replaces a piece of metal that sits between the camera and its original hinged arm. The arm mounts to the 2020 rail previously mentioned, which is mounted on the front of the lowest shelves.

Oscilloscope Probe Holders

This design popped up on the FunctionalPrint subreddit just in time. I was struggling with what to do with my scope probes – coil them next to the scope, keep them in a bin and pull them as needed… this solves that problem. The design comes from JRucks and is now on Thingiverse.

‘Hot Shoe’ Microphone Mount

I’ve had this one kicking around for awhile to hold my cheapy Takstar SGC-598 microphone. It’s not the fanciest setup, but for my casual purposes it’s more than enough. The design comes from Asgeirom on Thingiverse.

Solder Roll Holder

I didn’t really see the point of having a solder-roll holder until I printed one. Never again will that 1 lbs roll go walking across the desk (or onto the floor) in the middle of a tricky joint. This design comes from Phredie on Thingiverse.

“Pencil Cups”

These multi-purpose cup was one of the first designs I ever printed, and it’s still my go-to print for sampling the color of a new filament. It’s meant to print in spiraled-contour mode, which means that the outer perimeter (after the base) prints in one continuous revolving motion, instead of stepping up layer by layer like a typical print. There are perhaps a dozen of these scattered around the apartment, but since the reorganization, most live just above my desk holding, individually: pens/pencils, colored sharpies, black/silver sharpies, screwdrivers, pliers, flush cutters, cutting tools, and misc tools.


The next improvement to my setup is definitely a lighting improvement – its not terribly bright in the room to start with, and the shade from the shelves doesn’t help. 3D printing will be involved.

I also put my new setup to the test for the first time last night as I laid out a version of a DMX shield for the Arduino Pro Mini. Having all my tools organized and close at hand, and plenty of space to work it, makes working in my new setup a joy. The cleaning, the organization, the installing of new systems and setups: all worth it. It’s now fun to sit at my workbench, instead of a kind-of cramped pain. Onward!

Home Office Overhaul

You may get the impression from this blog that I like to dabble in a lot of different projects. You’re not wrong – I love trying new hobbies, new technologies, new recipies, new stuff. But one of the issues is that the old projects (and the pieces and tools that come with them) tend to pile up in my workspace. So with a kindly nudge from my partner, I decided it was time to overhaul my home office setup.

I wish I had taken a better series of before-during-after photos, but this photo that my partner took of me in the Fall certainly conveys the depths of the clutter of my old setup. It wasn’t always this bad… but sometimes it was:

The workspace in september, such as it was.

There were many inconveniences with this setup, but the chief one was a lack of actual open flat work area. This was mostly a result of:

  • The 3D Printer sitting on the desktop (and its control box)
  • The stack of test gear (oscilloscope, PSUs, SigGen) and my FT-767gx radio sitting in prime working area
  • This is/was my primary computer workspace as well, so any project that necessitated having a laptop on the desk meant almost no workspace leftover.

Additionally, a lot of the organizational systems that I had going were leftovers from days gone by, when I was doing more carpentry/assembly as part of a freelance career. The pegboard of hand tools, for example. But these days, while I’m glad I own, say, a carpenter’s square and a hammer, I only use them at home every 3-6 months. Removing the pegboard and the red pick bins you see in the photo above freed up valuable wall space. All my “carpentry” tools live in one large bin tucked underneath the desk.

I took inspiration from a couple of creative-types in my sphere: Jeremy KF7IJZ, ham radio nerd and one of the producers of the Ham Radio Workbench podcast; and Lee Fiskness, a fellow stage lighting colleague. Both have redone their home workspaces in the past couple years, and I know both pursue a variety of hobbies in relatively confined space.

1/2 of Jeremy’s setup, using ventilated wire shelving and a variety of bins. His desk sits to the right of this.
Lee’s desk setup. I’m amazed by the density of storage on this thing! Also, Lee being a lighting person, no surprise that there’s tasteful lighting built in.

While both Jeremy and Lee used the Algot System from Ikea, I ended up going with the Container Store’s version of wall-mounted shelves called ELFA. The primary reason for this is that it seems ELFA may be getting phased out – many of the specific components (metal shelves, certain size brackets) are no longer available. Additionally, ELFA’s two-slot metal vertical standards are compatible with lots of other generic brands (Rubbermaid, Closetmaid, Home Depot, Menards, etc.), and seemed more easy to create customized pieces for than Algot’s slotted-tab connectors.

Here’s the design I came up with, laid out in Fusion360:


I had originally intended to use Algot as well, so the specific shelf widths and vertical supports don’t quite align with the final ELFA design.

This makes use of my existing metal shelves and 72″x30″ desktop. The grey square on the floor represents the footprint of our elliptical, which also typically lives in this room.

The first step was to Marie Kondo the crap out of setup. I’ve tossed, condensed, consolidated so many things that I no longer needed, or that someone else who have better use for. I also purchased a bunch more plastic bins and part boxes, to try to break things down into manageable storage sizes.

About halfway through the clean. No more pegboard!

After a few weeks of cleaning and clearing, I went to the container store this weekend and picked up the major pieces for the shelving. The consultants at the ELFA counter are really expecting folks to walk in with not much of an idea of what they need to fill out their closet – I think they were surprised when I had a parts list and a drafting. But my consultant, who’s also a math teach, was a great help, and got me squared away in about 20 minutes. I did have to come back later in the week to pick up all the pieces, I think mostly because the store was slammed with patrons getting in on the ELFA sale.

The ELFA system is pretty straightforward – everything hangs off of dual-slot vertical “standards”. There are two types of standards – those that hang purely off a top rail, and those that don’t hang off a top rail but instead mount to the wall every 16″ vertically or so. I went with the first type, but being concerned about weight, I didn’t trust the Container Store’s claim that everything could just be hung from drywall anchors. Instead, I screwed a stained piece of 1×4 directly to the studs the whole length of the wall, and mounted the top rail to that. I also added 3 other matching 1×4’s down the wall, so the rails would have something to hang flush against.

As of March third, things have come a long way!

There a a few significant things I mean to add to this setup. One is some under-shelf lighting – I’ve ordered come WW/CW LED tape and aluminum channel to arrive soon, which will be a project in and of itself. And as for control, I think I’ll start with everything just wired to some switches, and then decide if I want to get fancy. (I had a long think in the shower about an Arduino-controlled, touchscreen connected dimming system, but that may be getting ahead of myself). Not sure yet if I’ll re-use the 2′ Fluorescent fixtures that had hung above the pegboard before.

The other thing I’m jonesing for is a whiteboard. Especially when trying to reason out a problem, I find doodling on a whiteboard to be both relaxing and clarifying. There’s now a big empty space on the far wall that I think will do nicely.

It’s so satisfying.

Lighting Control Protocols and Standards

The world of stage lighting uses a variety of communication protocols to link control devices (computers, light boards, houselighting systems) to endpoint devices (lights, dimmers, effects). These run the gamut from basic analog control through legacy serial protocols to modern packetized, ethernet-based protocols.

The specifications of many of the most widely-adopted protocols are managed by the Entertainment Services and Technology Association through their Technical Standards Program. Confusing matters slightly, these protocols are sometimes referred to by their ESTA standards numbers, often interchangeably with the common names. Below is a list of the major ESTA standards that apply to lighting control, with their standard number, their common name, and a brief description.

I’m not directly linking to the standards documents, but you can find them all on the approved standards page of the ESTA.

Here are the currently released standards:

Document #Short Name
E1.30-10V Control
E1.11DMX 512
E1.17ACN
E1.20RDM
E1.31sACN

Briefly, the protocols are:

E1.3 0-10V Control: Specifies control of dimmers/luminaries via individual analog control lines. 0 volts is always off, or one extreme of a parameter (e.g. full pan left; minimum blue; focus all the way in, etc). 10V is always on, or the other extreme of a parameter. “0V” is really -0.2V to 0.3V. “10V” is really “9.8V to 30V”. Control lines must be stable to ± 20mV. Minimum load impedance is 50 kOhms. Passive controls have max 2.5 kOhms output impedance; active controls have max 100 Ohm output impedance. Short circuit protection, overvoltage protection, and current supply are also specified.

E1.11 DMX 512: (“Digital MultipleX“) Specifies a 250 kbps serial protocol for controlling equipment, the EIA-485 transmission techniques for the same, physical cable specifications, and appropriate connectors (XLR5). The 5-conductor cables are common, data 1±, and data 2± (rarely used), each not to exceed 6V above common. Data lines are balanced in pairs. Signal line impedance is 120 ohms nominal. Each “packet” of serial data begins with a break, mark, and start code, followed by up to 512 slots of data, each of which has an 8-bit value. No error checking/correction is provided.

E.1.17 ACN: (Architecture for Control Networks) Specifies a series of protocol formats for (generally network-based) interchangeability between control systems and endpoint devices. Generally: the Device Management Protocol (DMP) encapsulates the Getting and Setting of device parameters; a set of Device Description Language standards (DDL) defines the format and language for component description to allow common control and identification; and the Session Data Transport (SDT) protocol allows for multicast delivery of messages with ordering and verification not present in generic UDP multicasting. The Protocol Data Unit is the singular message format for DMP messages.

ACN also provides for device discovery. While typically used with TCP/IP and 802.3 Ethernet or 802.11 WiFi, other physical/link/transport/network layers are incorporated as possibilities, including various serial and RS485 standards, via interoperability profiles.

E1.20 RDM: (Remote Device Management) Specifies an extension to a DMX512 link permitting intelligent, bi-directional communication between devices. An alternative start code in a DMX packet identifies an RDM packet. RDM uses a binary-tree or similar search to identify devices on a DMX512 line. Controllers can use RDM messages to Get or Set parameters of endpoint devices, and communicate to individual endpoints when they may drive the line to respond to Controller commands. Device configuration and monitoring are primary goals, as is identification.

E1.31 sACN (Streaming ACN): Describes a lightweight mechanism for streaming DMX packets over an IP network using a (small) subset of the ACN suite. Describes data format, protocol, addressing, and network management, as well as a synchronization method for ensuring that data arrives concurrently at multiple endpoints.

There are also some subsidiary standards documents managed by the Control Protocols Working Group, including:

  • E1.27-1 – Standard for portable control cables for use with DMX512
  • E1.27-2 – Standard for Permanently Installed Control Cables for use with DMX512
  • E1.30-1 – EPI 23, Device Identification Subdevice
  • E1.30-3 – EPI 25, Time Reference in ACN Systems using SNTP and NTP
  • E1.30-4 – EPI 26, DDL Extensions for DMX512 and sACN Devices
  • E1.30-7 – EPI 29, Allocation of IPv4 Addresses to ACN Hosts
  • E1.37-1 – Additional Message Sets for E1.20 RDM Part 1 – Dimmer Message Sets

In addition to the published ESTA standards, it’s worth mentioning two that are not currently maintained as standards:

The standard for E1.33, RDMNet, has been in draft review since at least 2011. It defines a suite of protocols for the types of device discovery, device management and configuration, and automatic device configuration that RDM provides on a DMX512 link, but across a network. It defines a broad scalable architecture that allows for multiple controllers and “tens of thousands of responders,” as well as a minimal protocol for carrying non-RDM data over the same protocol. The spec defines

  • A Low Level Recovery Protocol (LLRP), used to configure IP settings so that E1.33 equipment achieves connectivity
  • A Broker protocol, which allows for discovery and many-to-many message transport
  • The RDM Packet Transport Protocol (RPT), which defines the primary packet formats and messages, as well as topology and functional requirements for controllers and endpoints
  • The Extensible Packet Transport protocol (EPT), which may be used to carry non-DMX data in a similar way to RPT.

BSR E1.33 Concluded its fifth public review in January 2018 with 68 pages of public comments; no date is known for the next public review session. As noted below, ETC has its own mechanism for transporting RDM and RDM-like data over ethernet via its NET3 suite.

The second ‘standard’ of interest is the former E.1.45, “Unidirectional Transport of IEEE 802 Data Frames over ANSI E1.11 (DMX512). This provided a mechanism for transmitting IEEE 802 packets – including Ethernet (802.3), Wireless LAN (802.11), and Bluetooth (802.15.1) – over a DMX512 link by using an alternative start code, stuffing the packet data into the DMX “payload” area, prepending two byte of sequence numbers and appending a two octet CRC for error checking. Interestingly, it seems that this standard was aimed specifically at Visible Light Communication (802.15.7), for transmission of data in the visible spectrum.

After publication, it was established that key parts of the E1.45 standard were covered by US and Korean patents, and the patent holder would not guarantee that licensing could be made “under reasonable terms and conditions that are demonstrably free of any unfair discrimination.” Therefore, in October 2015, the ESTA withdrew this document as a standard.


Beyond the ESTA-specified standards, there are a handful other vendor-specific or genre-specific communications protocols in use. Electronic Theatre Controls (ETC) has used a number of protocols all their own over the years, including:

ETCnet (Net1): Originally called ETCNet and retroactively renamed to Net1, this was ETC’s first Ethernet based control protocol. It is proprietary, without publicly available specification. It is a raw Ethernet protocol (layer 2), meaning that routers and certain types of switches do not pass Net1 traffic. A hub is recommended. Net1 provdes transport of console video information, up to 4 universes of DMX, tracking backup data, and keyboard command information to ETC products of the era, including Express/Expression/Insight and Obsession 1. Many Net2 DMX nodes can also be configured to operate in Net1 mode, with the concomitant loss of function.

ETCLink: ETC’s Sensor dimmers with a CEM classic controller use this protocol to provide dimmer feedback to the console. Express/Expression and Obsessions 1/2 consoles could receive this data. Connections were commonly a 6-pin XLR connector. This functionality has been supplanted by ethernet-based feedback in modern systems.

ETC Net2: Introduced with the Obsession II console, ETC’s second networked control solution incorporated IP addressing, this allowing network traffic to be switched or routed. Sends DMX data as eDMX, which in its final version incorporates per-“range” priority. Includes EDIMI, ESMPTE, FTP for ETC devices, and video data for remote video units.

ETC Net3: ETC’s current suite of network-based communication. Sends DMX data over sACN. Uses a non-public RDM-over-ethernet protocol to receive RDM data from Net3 DMX Nodes. Incorporates network video data as Net2 did. Many ETC products (Sensor Dimming, Paradigm, Mosaic, Unison, etc) have ethernet functionality, but it is nebulous which of these fall under “Net3” and which are their own Ethernet-based communication system.

ETC also uses LonBus-based networking devices to control various legacy architectural control stations – while their modern counterparts can also usually take LonBus, they are typically served by an Ethernet connection.


Other situation-specific lighting communication protocols include:

Art-Net: A simple implementation for streaming DMX512 and RDM information over IP networks, typically ethernet. Multiple versions exist (1 thru 4) with significant differences – version 1 uses only broadcast packets; version 2 uses broadcast for discovery of endpoints and unicast for data delviery. Version 3 introduced the ability to expand to up to 32,000 universes, and further refinements were made to version 4. Artnet uses specific IP ranges for much of its configuration, which can present integration challenges when it needs to exist alongside other switched protocols.

HogNet and Fixturenet: High End Systems uses its proprietary HogNet ethernet suite of protocols to link its line of Whole Hog lighting consoles, as well as their DMX processors and optionally other lighting control PC’s. These connect to a specific HogNet RJ45 connector on the back of most Whole Hog consoles, with its own NIC. A secondary connection, the FixtureNet ethernet connection, is used for connecting to Art-Net/sACN(E1.31) DMX gateways.

CITP (Controller Interface Transport Protocol): Used by some lighting and video controllers to exchange pictures and video streams over a network. The standard is maintained by Capture.

PosiStageNet (PSN): An open protocol developed by MA Lighting to transmit realtime position information over a network, for example from a tracking device on a moving actor, scenic piece, or prop to allow for video, lighting, or motion-control tracking.


So what does the future of lighting control look like? Clearly, we are living in an increasingly-connected theatrical world, and most of that connectivity is Ethernet-based. I don’t expect to see an entirely new paradigm at the link layer any time soon.

I have expected for many years to see an additional level of automation and abstraction in how we set up lighting systems. When all of the devices in a system can talk to each other, is there still a need to individually plan, address, patch, and coordinate the ID’s of individual fixtures or dimmers? Or can we automate ourselves out of the time consuming business of managing how the devices talk to each other and let the system set up its communication network automatically? We shall see.

No matter what the future holds, we’ve come a long way from Piano Board dimming.

Update: After posting this on Facebook, a friend asked about the AMX protocol that he remembered from high school. Here’s the brief answer I gave him:

AMX (Analog MultipleX) was one of a bunch of protocols (AMX192, CMX, MPX) that appeared in the late 80’s as people were trying to solve the “one dimmer = one wire” problem of E1.3 0-10v. It used 4 wires – two for a (balanced) clock signal, one ground, and a signal line which carried a succession of analog voltages (0-5V) that represented the levels of up to 192 parameters.

Acceptable connectors were 4-pin XLR or TY4F (mini-stupid!). Interestingly, the spec requires “sound-style” Male XLR connectors on the controller and female connectors on endpoints. 

The AMX192 standard was developed and published in 1987 by the United States Institute for Theatre Technology (USITT), instead of the ESTA.

Full spec re-hosted here: http://jeff.glass/documents/AMX192_8-08.pdf

CDV-720 3A High Range Radiation Meter

This post is cross-posted to my ham-radio specific blog, kk9jef.wordpress.com

I went to the WCRA Hamfest in St. Charles this weekend in search of test gear (I had been fortunate to find a working Heathkit IM-2420 Frequency Counter there a couple years ago). I didn’t come away with anything of that sort, but I did scoop up this yellow beauty:

This beaut is a CDV-720 3A High Range Radiation Meter. It’s a remnant of the early cold war, the beginning of the atomic age – thousands were produced in the late fifties and early sixties by the Victoreen Company out of Cleveland Ohio. It’s got a cast aluminum case that feels like it’s made to survive a bomb, and maybe it was. The manual notes that:

It is designed to be used by radiological Civil Defense personnel in determining radioactive contamination levels that may result form an enemy attack or other nuclear disaster.

The really staggering thing about this meter is the range it covers: up to 500 Roentgens/hr. At that rate, your goose is cooked in a matter of minutes (first metaphorically, then literally).

Here’s a brief video overview of the meter, its circuitry, and the scary-high levels of radiation that it’s meant to measure:

Stay safe and non-irradiated out there!

Homemade Cheddar Cheese

Over the past 12 months or so, I’ve dipped my toes into some basic cheesemaking, including cream cheese, farmer’s cheese, and ricotta. But for me, there’s no better cheese than a sharp white cheddar, and with an eye toward making cheddar and some other hard cheeses, I’ve built my own cheese press and my own first hard cheese.

The process I used to construct the press is very similar to this instructable. I used a 1x6x48″ Maple board from Menards as the base, and two pieces of 1×2 Poplar from an earlier project. The threaded rod, nuts, wingnuts, and washers are all 3/8″ hardware. I added four threaded furniture feet to raise the press off the countertop and allow for tilting the press slightly to allow the whey to run off. I used some butcher-block conditioner to help seal the wood before use. (Having access to a theatrical scene shop helps.)

My first pressed cheese is a “farmhouse cheddar”, made according to this recipe from Gavin Weber. Specifically, the ingredients I used were:

  • 2 Gallons (4 half-gallon containers) of Kalona Whole Milk from our Fresh Thyme Market. While unpasteurized milk seems to be recommended for a lot of artisinal cheese making, that’s hard to come by in urban Chicago, so this non-homogenized milk is the way I’ve gone.
  • 1 Sachet of Mesophillic Culture, purchased from Pursuit Supply Co, a small business here in Chicago that focuses on homebrewing and distilling, cheesemaking, and film development.
  • 1/2 tsp of Liquid Vegetable Rennet, also from Pursuit Supply
    • This was diluted in 1/4 cup of bottled (unchlorinated) water before adding, since apparently chlorine kills the coagulating action of the rennet
  • 1/2 tsp of Calcium Chloride (from, where else, Pursuit), also mixed with 1/4 cup bottled water. I understand this introduces more soluble calcium to the mixture and helps the curds to form.
  • 2 generous tbsp of non-iodized sea salt.

The process, as outlined by Gavin (of Little Green Workshops) is straightforward. Here is is summarized by me, with comments as to how my own process went:

  1. Sterilize all materials that will come into contact with the milk or cheese.
    • I used a preparation of Star-San mixed with water in the recommended ratio of 1:640 (1 Oz per 5 gallons). I soaked the large stirring spoon I planned to use, as well as all the measuring cups in this for a few minutes. Meanwhile, I boiled a couple quarts of water in my large stockpot to sterilize the pot itself, then wiped the lid down with the Star-San mixture.
  2. To a large stockpot set up as a double-boiler, add the 2 gallons (8 liters) of milk.
    • I used one of my large general-purpose pots underneath my stockpot as a double boiler, and it was remarkably stable.
  3. Heat the milk to 33C (92F)
    • This took about 20 minutes with my double boiler setup.
  4. Stir in the diluted calcium chloride
  5. Sprinkle the starter culture over the top, then stir for 1-2 minutes to incorporate
    • Gavin’s recipe calls for 1/8 tsp of culture, I simply used one small sachet.
  6. Cover, and allow the milk to ripen for 45 minutes
    • This allows the culture to start to grow a little and the milk to begin to acidify
    • I turned off the heat at this stage to allow things to maintain their temperature, but when I returned after 45 minutes, the temperature had shot up over 40C! Oops!
  7. Stir in the diluted rennet while stirring. Stir for no more than a minute as the milk with start to set.
    • I treated myself to a very large metal spoon for this project
  8. Check for a clean break with a clean finger
    • Basically, stick a finger in through the top layer of curd – if it feels firm-ish, it’s good to go. If it’s a little soft and yogurt-y, you can cover and wait another 10 minutes or so.
  9. Cut the Curd
    • There are some fancy curd cutters out there that look like a wire mandolin or harp, but I just used a long clean knife, run through up-down, left-right, and twice angled.
  10. Slowly heat the milk and curds to 38C (100F) over about half an hour
    • Even with a double boiler setup, my setup took a little modulation (higher heat, lower heat, higher heat) to not spike in temperature too fast. I took about 25 minutes to raise the temp up to 38C, sitrring continuously
  11. Let the curds rest for 10 minutes at 38C
    • At this point, I should have taken the pot off the double boiler, but I figured it would help keep the milk warm. It sure did – by the time I returned 20 minutes later, the temp was up to 44C! It remains to be seen whether this will have a negative effect on the cheese.
  12. Drain the pot into a clean cheesecloth-lined colander
    • I collected the Whey at this point and made a Whey Ricotta out of it. Yum!
  13. Tie up the edges of the cheesecloth and hang for an hour to drain some of the whey out
    •  I had a spare bit of PVC pipe leftover from my multiband antenna project, so I set that between the backs of two chairs and set the pot underneath to catch the drippings.
  14. After an hour’s dripping, transfer the curds back into a pot. Break the cheese mass into walnut-sized pieces. Toss 2+ TBSP of non-iodized salt throughout.
    • I used non-iodized sea-salt, instead of some of the products which are marketed as “cheese salt.” Not sure what the difference is
  15. Line a sanitized cheese mold with a sanitized cheese cloth. Transfer the curds to the press. Flip a corner of cheese cloth over the top of the curds, and place the follower on top.
    • I originally tried 3D printing a mold, but I got cold feet about subjecting a 3D print to 50+ lbs of pressure overnight, fearing it would crack. I also thought it would be good to seal the PLA with polyurathane or similar before trusting it to be food-safe. So I made a simple press out of a plastic jug from Walmart with the bottom and handle cut off, and holes punched through the sides.
  16. Press for 10 minutes at ~10 lbs.
    • I set up my press in a low-sides baking sheet to catch the whey as it ran off, and used the threaded-feet to set the press slightly off plumb so the whey all ran off one side.
  17. Remove the curds from the press and cloth, turn over, and press 10 minutes at ~25 lbs.
    • Quite a lot of whey running off at this point. Fairly cloudy, which I read is not good, but I’m not sure why…
  18. Remove the curds from the press and cloth, turn over, and press for 12 hours at ~50 lbs
    • I left the cheese to press overnight, checking it once a couple hours and tightening the springs a bit.
  19. Remove the wheel of cheese from the press and cloth. Trim any bits of cheese that have popped up around the follower.
    • Leave these in the fridge for a couple days and they’re basically cheese curds! So tasty!
  20. Place the cheese on the counter under a bit of cheesecloth or similar to air-dry. Turn twice daily until it has a nice rind and is quite dry to the touch.
    • I left my cheese on the counter for a little under 3 days before waxing. Possibly I should have left it longer to develop a drier rind, but we shall see when we break the thing open.
  21. Wax or vacuum seal the cheese
    • After drying for a couple days, the options are to either cloth-band, wax, or vacuum seal the cheese to prevent any nasty bugs getting into the cheese.
    • One of Gavin’s most popular videos describes Cloth-Banding the cheese, but in his final tasting of that cheese, he describes the process as too fiddly (and he did get some mold in a bit of that cheese early on). So I decided to wax the cheese instead. Pursuit was sadly out of cheese wax (soft parafin-based wax) when I stopped by, so I ordered some Beeswax from the internet to arrive the next day.
  22. Age the cheese for 1 month to… forever?
    • Currently, the cheddar is aging in a small mini-fridge in the basement, though with it being the early  months of winter, the fridge is turned off and is just functioning as an airtight box. I added a small dish of water and a small dish of saturated salt to raise the relative humidity to around 80-85%.

So… now we wait! I’m thinking, with this being a first cheese, we’ll crack it open around valentine’s day (~3 months) to see how I did, then possibly re-seal it and age longer if it seems like everything’s going well.

One next step will be to measure the pressure that my chosen springs will create when the press is tightened down entirely. I discovered that my bathroom scale doesn’t fit within the scale, so much like the instruct able suggests, I’m putting together a test jig with a wider base to allow me fit the springs around the scale and make a weight gauge. I’ll also need to replace the felt-bottomed feet with something that doesn’t absorb whey (I threw the feet out after this batch).

Here’s hoping it all turns out well!

150 Switches

I got lots of wonderful little gifties for my recent birthday, but one of the most out-there was a bag of 150 Assorted Rocker Slide and Toggle switches from Jameco. It’s literally a 2 pound scoop of switches in a plastic bag, sealed and mailed. Thanks Mom and Dad!

I spent a good 10 minutes sorting it out – here’s all that squinched into 45 seconds:

So, what do you get in a two pound sack of switches? Well, after another hour or so of cataloging, here’s the results:

(It’s exactly 150 switches! Well I’ll be…)

Quantity Genus Action Poles Description
11 Rocker ON-OFF-ON 1 Large Black
15 Rocker ON-OFF 1 Large Black
3 Rocker ON-OFF 2 Large Tan Power
9 Rocker ON-OFF 1 Medium Black
3 Rocker ON-OFF 1 Round Black
2 Rocker ON-OFF 2 Round Black
11 Rocker (ON)-OFF-(ON) 1 Medium Red
4 Rocker ON-OFF 2 Large Black Illuminated
4 Rocker ON-ON 3 Medium Red
11 Rocker ON-ON 1 Panel-mount Red
2 Rocker ON-ON 1 Right-angle mount
2 Rocker ON-ON 2 Right Angle mount red
1 Rocker ON-OFF-ON 1 Medium Blue
1 Rocker ON-OFF 1 Small Black
2 Rocker ON-OFF-ON 1 Large Red/Green Illuminated
8 Pushbutton ON-(ON) 1 Right angle plunger
11 Pushbutton ON-(ON) 2 Spring-loaded plunger
5 Pushbutton ON-(ON) 2 Small red/white plunger
2 Pushbutton ON-(ON) 2 Small black plunger
2 Pushbutton ON-(ON) 2 Small blue plunger
2 Pushbutton ON-(ON) 2 Tiny pushbutton
2 Pushbutton ON-(ON) 1 Panel mount square illuminated
2 Pushbutton OFF-(ON) 1 Grey rectangle illuminated
3 Slide ON-ON 2 115-230V Selector Switch
5 Slide ON-ON 2 250V-rated slide switch
2 Slide ON-ON-ON 2 Small silver 3 position
4 Slide ON-ON 1 Tiny slide switch
1 Slide ON-ON 2 Square blue slide switch
4 Dipswitch OFF-ON 2-Lever Red Dipswitch
1 Dipswitch OFF-ON 4-Lever Dipswitch
1 Dipswitch OFF-ON 5 Lever Dipswitch
1 Microswitch OFF-(ON) 1 Microswitch w/ 4″ tails
2 Microswitch ON-(ON) 1 Black microswitch with trigger
4 Pushbutton OFF-(ON) 1 Blue breakboard pushbutton
4 Pushbutton OFF-(ON) 1 Illuminated breadboard pushbutton
2 Pushbutton OFF-(ON) 1 Misc tiny pushbutton
1 Keyboard Switch OFF-(ON) 1 Large grey keyboard switch
(5) Cap Round black button cap
150 TOTAL