UncategorizedComments Off on Adding DMX Scene Recall to a Dolby DS220 Media Server
From time to time, on the other end of a phone call is a variation of a problem we’ve not come across before. Over the years, our gear has integrated well with equipment from AMX, Crestron, Control4, Lutron, Savant, and many others. This was the first time we’d officially been asked to help with a Dolby-based platform.
In short, this group needed to record a handful of DMX scene presets and recall them using their existing theatre automation system. Though the stock DMX record / playback firmware we shipped worked perfectly, the installed Chauvet LED fixtures downstream weren’t able to handle full-speed DMX, an issue we solved clear back in 2011. (For the curious, that story is described here.)
It took just a few minutes to pull the ‘slow speed’ DMX output routines from our library and recompile the DecaBox firmware. Fortunately, the system updates easily in the field via USB; the installation has worked perfectly ever since.
From the customer:
Our venue features a relatively old DMX network–and a scene recall system that is somewhat of a relic. When tasked with finding a way for our Dolby DSS220 Media Server to trigger lighting changes during film screenings, interfacing with that system’s contact closure system was out of the picture given the tight time frame. After contacting ESINC, it sounded like the Decabox was the easiest way to go. The scene recording procedure was painless and quick, and the separate dmx “output” and “through” makes the system exceedingly simple to set up. In addition, the serial command set is easy to master as well.
At one point, I noticed some glitchiness with some of our Chauvet LED fixtures. John Chapman, having dealt with the exact problem in the past, quickly wrote us new firmware that would slow down the DMX output baud rate, which immediately solved the problem.
Thanks for the speedy turnaround, John!
Julian Amrine, Shoreline Community College Theatre
As is often the case, customers and designers who find our corner of the Web are working against nearly impossible deadlines. This most recent request, late on a Thursday afternoon, was a fun one to fulfill. Their project included DMX lighting in four discrete zones, and they required two separate operating modes:
“We need an untrained operator to trigger a specific sequence of cues using a large pushbutton” & “We need a specific complicated DMX sequence (specifically, a rolling color scroll across about a dozen fixtures) to loop indefinitely.” Naturally, the drop-dead delivery date was in two business days.
Prior to our phone call, they were prepared to spend about $8k on several ‘standalone’ DMX consoles. We were thrilled to offer a more economical and flexible solution.
In the past, we’ve shipped several different versions of a circuit board containing DMX in, through & out jacks, along with an assortment of dry-contact-closure inputs. This card, when loaded with the correct firmware, could record DMX snapshots (a single frame of data) or capture in real time (44 frames per second). Then various snapshots and dynamic scenes can be replayed based on external triggering. Unfortunately, the shop shelves were empty of these cards, and there wasn’t enough time to make new ones.
As an aside, there’s a full service circuit board manufacturer right here in town. We use them for quick-turn work and sensitive designs. Over the years, we’ve occasionally requested four hour (!) turnaround, from email CAD file receipt to courier pickup at their shop. This service isn’t cheap, but it’s remarkable that such things are even possible these days.
So moving to Plan B: Our shelves are packed with a new batch of DecaBox chassis sets, assembled and ready to be loaded with firmware. How to quickly add rugged, reliable, remote pushbutton input without changing any existing hardware, drilling holes in chassis sets, or making a huge mess?
The answer, after some pondering, was a riff on how industrial automation systems communicate with external sensors: a current loop. The most popular version is called 4-20mA, representing logic low and high values respectively. If 4 mA is flowing in the wires, the logic level is zero. If 20 mA, logic is one. And in the industrial world, if ZERO mA are flowing, or if 20+ mA are flowing, a fault with the cable or sensor is assumed, the system squawks and repairs can be made.
In alarm systems, window and door sensors work in a similar way. ‘Open’ is one current value, ‘closed’ is a second. No current flowing at all means a cut wire, so phone the (now overseas) mothership and complain.
Now, the DecaBox doesn’t normally communicate with industrial sensors, but it does contain a rugged, buffered, industry-standard, short-tolerant, high voltage RS-232 interface. Our quick & dirty solution was to transmit a repeating, pre-defined data stream on DB-9 pin 3, the usual TX pin and then listen for its presence on the receive pin.
A handful of standard shielded M-F DB-9 cables, 6′, were sacrificed for the cause. On the chopped-off female end, wires corresponding to pins 2 & 3 were connected to the normally closed terminals of rugged arcade pushbutton switches. These switches are nearly indestructible and would mount perfectly on the wall of the booth / installation.
During regular operation, the DecaBox transmits serial data and listens for loopback. If they match, the wiring is correct, the button is undisturbed, and nothing happens. But once loopback breaks and no data is received, the DecaBox knows it’s time to read the pre-stored DMX cue sequence from the internal memory card, send it to the outside world, then resume waiting for a new contact event.
Simple & elegant & shippable within about six business hours, including testing and verifying new snippets of source code.
Oh, and scenario #2? Perpetually looping DMX scene playback? Trivial to accomplish using our stock recording and playback firmware. A complicated scene can replay until power is lost or the cows come back, whichever comes first.
We ended up shipping 4 separate DecaBoxes, one for each lighting zone. Two were pushbutton triggered and two set up to loop their internal scenes. Of course, the firmware is user-selectable to run in either mode, based on settings made using the panel LCD and pushbuttons.
Need something similar? We’d love to hear from you.
We’re happy to have released a version of the DMX Engine with RJ-45 outputs. Many of our customers use regular CAT5 cable and terminations as a backbone, and this version of the engine was designed to make their lives simpler. Also, many low-cost DMX decoders use RJ45 connections for data in and through.
The system works exactly the same as before – each output has its own drive stage which can feed a minimum of 32 connected DMX devices. We chose genuine Neutrik EtherCON jacks for durability and rugged design. The output pinout matches the current ESTA standard: data on the orange / orange white pair and ground on brown.
Grab yours today in our online store. Outside the US? We’re thrilled to ship directly using DHL, UPS, FedEx or the postal service. Alternately, check with a nearby distributor.
We were contacted by an integrator whose DMX fixture installation was large and complicated. They were using a Control4 system and chose our RS-232 DMX Engine as the master output controller in their system. However, in their case the standard practice of daisy-chaining large groups of fixtures* together was impossible, due to the required physical layout, access to connected conduit, etc.
During a telephone consultation, we discussed installing multiple DMX Engines throughout their venue. Because of the required layout, this would have been quite expensive. When we learned that their timeline was fairly relaxed, it made sense to commission a rack-mount system with 12 outputs, 12 isolated output drivers, and genuine Neutrik EtherCON jacks for easy termination of their installed wiring. Our friendly metal shop across town returned two pair of blue-anodized chassis sets a few weeks later:
The system follows the now-standard pinout for DMX over CAT5 cable. We use the DATA 1 pair (orange) with both brown conductors grounded:
This rack-mount DMX Engine functions exactly the same as its smaller red brethren. The command set is identical; only the form factor and output count have changed. Need one? Let us know.
*This was the subject of a tech support call earlier in the week. When playing in the DMX world, there are two numbers to keep track of: channel count and fixture count.
Channel count is fairly obvious: a full universe of DMX contains 512 separate channels. This means that 512 single AC dimmers could drive 512 discretely connected incandescent light bulbs. When the author got started in technical theatre, the entire venue was controlled by large, dusty, hum-emitting 6 KW dimmers. About 30 worked properly. The command ‘set all to full time zero’ provoked a physical, visceral reaction from offstage left.
If using RGB LED fixtures, a universe can discretely control 512 / 3 = 170 fixtures without any overlap. Some modern moving lights à la rock concert gobble up 100+ channels each, which means only five can be individually driven on a single universe.
Recently, we completed a Christmas art installation where a single tree required nearly 23,000 channels of data running at 50 frames per second. We used e1.31 / sACN (DMX over ethernet, more or less) as the control backbone.
Fixture count is a different beast altogether. It relates to the total electrical load on the differential bus (D+ and D-, the DMX data signals). Each fixture connected in a daisy chain increases the load, and if it’s too high, signaling can turn erratic and be difficult to troubleshoot. Here’s a great article which dives deeper into the math. In any case, the ‘standard’ load for an RS-485 receiver (and by extension, a connected DMX device) is 1/32, which means that 32 devices can be safely daisy-chained together and driven successfully by a single master controller. If fixture load isn’t explicitly called out in a device’s datasheet or instruction manual, assume 1/32 load.
For slightly more money, some manufacturers (including us, as has been required by clients from time to time) design DMX input stages with 1/256 load receivers, which allows up to 256 devices in a single daisy chain without introducing signal issues.
Bottom line: make sure both your channel count and fixture count are within acceptable ranges. If fixture count is too high, consider using what’s called an optosplitter, which receives a signal and then regenerates it multiple times across multiple outputs. Or call us and we can help with something custom.
In addition to the standard products listed in our web store, we do quite a bit of custom / one-off work. Here’s a collection of recent quick-turn projects we’ve recently shipped. All images here can be enlarged with a click.
The DMX Triggered DMX Selector Switch
A theatre up north had several lighting control sources (a large lighting console, several wall panels, etc) plus safety rules which require certain channels be kept at a specific intensities 24/7. Based on their sketch and pseudocode, we designed a five input DMX router.
For any input, setting a specific channel to a specific value lets that DMX source take control, and its full universe of data is passed to the ‘DMX Out’ jack. In addition to switching between the five inputs, the system forces the safety channels to their proper values and sends the final signal downstream.
If you think about it, in this situation, a standard DMX merger running either ‘highest takes precedence’ or ‘most recent takes precedence’ wouldn’t work properly. The system contains a USB interface for painless field firmware updates if they’re required. Each DMX input is optically and galvanically isolated from its neighbor, which should keep lightning propagation to a minimum.
Side note #1: Our stock DMX receive circuitry has been installed in thousands of locations worldwide. And in over a decade, we’ve never, ever received a report of it being damaged in any way.
A Countdown Timer / High Power UV Trigger System
Though not one of our usual DMX / MIDI / serial projects, we’d worked with staff at this childrens’ museum several times in the past. It’s rewarding to deliver something which didn’t exist, anywhere in the world, until we made it so.
In a dark corner of the museum’s ‘color and light’ lab, an entire wall was painted with photoluminescent paint. When excited by a xenon strobe light, flashlight or blacklight, the paint activates and glows green for several seconds, slowly fading away as the energy dissipates.
The designers envisioned a ‘photo booth’ where patrons could press a trigger button and then pose against the wall. The paint is then activated by the light source, leaving a glowing silhouette.
We sourced a pair of 10W UV lights (395 nm and super intense, causing mild eyeball sunburns after twenty seconds of near-field exposure) and a 4″ illuminated pushbutton.
I felt that standard 7-segment displays looked mechanical and dated, but a quick search online returned a slightly stylized 7 segment font – ‘Modern Mini’ in bold italic. The ~5 degree slant looked fun, and I liked how the segments jauntily meshed together.
It took a few steps in the CAD program, but the digits were converted to vector data. On the shop’s laser cutter, we created a 7-segment display measuring 300 x 200 mm. The display was loaded with LEDs whose brightness and color can be arbitrary controlled, segment by segment. The finished assembly is a sandwich of several acrylic layers, using black, clear and white stock. The segments are inlaid in the black layer, then covered with a clear protective layer. The layers allow the light for each segment to be channeled, diffused and displayed in a pleasing way.
Also, the giant pushbutton contains a white LED which can be set to any intensity.
Our custom circuit board include a small display for changing and storing settings (UV / flash exposure time, countdown time and ‘timeout’ time). It was somewhat overbuilt, supporting 4 contact closure inputs, 4 buffered logic level outputs, a pair of high power output stages and 4 SSR (solid state relay) outputs, in addition to connections for the countdown display and a smattering of indicator lights.
During normal operation, the display reads ‘5’ in green, and the pushbutton pulses slowly, à la sleeping iMac, drawing attention to itself in a tasteful way. When the button is pressed, the white LED turns off and the countdown begins. At time zero, the UV sources pulse for their specified time, the display switches to blue and begins begins counting down from the ‘lockout’ value, giving patrons a chance to enjoy their artwork as the phosphorescence slowly fades away.
Once the lockout time has passed, the pushbutton resumes its quiet pulsing, the display switches back to green and waits patiently for input.
Side note #2: The blue / green color scheme was chosen in a nod to the industrial designers at Disney. Green means go, blue means wait. Red signifies danger and problems, so don’t bother the public unnecessarily.