Halloween DMX lighting and sound – introduction

Years ago, I worked with a local guy on bringing in computer controlled lighting and sound to a local haunted house attraction. The original attraction just used light bulbs of different colors and actors to make everything happen. Our upgrade included the following:

  • We used a cheap Windows PC and VenueMagic show control software.
  • We ran a chain of RGB DMX lights was ran throughout the attraction.
  • About 14 speakers were installed, all wired back to a stack of cheap Pyle brand amplifiers.
  • A cheap USB hub and some $2 USB sound cards was used to get multi-channel audio from VenueMagic, and it worked great.
  • We installed pressure mats to trigger audio and effects.
  • I built an Arduino input box to read triggers from pressure mats and send them to VenueMagic as serial data.
  • There was also a DMX controlled relay board that was used to trigger air jets and control pneumatic doors.
  • When building regulations changed a few years into operation, the haunt was wired with illuminated exit signs and smoke detectors. Those were brought into the system so it could halt the show and turn on white work lights for safety.

The end result was a living, breathing attraction with flickering “flame” light, atmospheric moonlighting, strobe effects, as well as immersive surround sound throughout.

The VenueMagic software was, by far, the most expensive element of this project, and also the one that provided the most headaches. While the software itself was amazing and powerful, running on Windows was not. We had numerous issues over the years with Windows crashing, USB devices failing to be recognized, audio devices being remapped (requiring editing the show control configuration), etc.

Once the computer was in control, if it went down, you lost the entire show. The lights had a backup mode (we called it “party mode”) where they would begin randomly cycling through colors if there was no DMX signal. At least it didn’t leave the guests in the dark, but a silent haunt with circus lighting was far from scary.

In upcoming articles, I plan to discuss various ways you can show with complex lighting and audio, and make it play without needing a PC.

Just in time for the holidays ;-)

4 thoughts on “Halloween DMX lighting and sound – introduction

  1. MiaM

    Interesting! In the mid-late 90’s me and some friends buildt a dot matrix display using 40W mains powered light bulbs. We buildt it in two stages. Stage one was three boxes of 8×8, giving a total of 24×8 pixels, and all three boxes were controlled by a micro controller which in turn recieved DMX data from an Amiga. Amigas serial port can be set at 250kbps and when only transmitting there is no problem with not having any real hardware bufer (or DMA), however we cheated and only sent a few more channels data than we had hardware to display. That way we got enough cpu time left over after the 50Hz interrupt routine had sent the DMX data.

    Later we added six more 8×8 boxes. Theese had buildt in microcontrollers recieving DMX data. We managed to squeeze in opto couplers, a small mains transformer, 5V regulator, shift registers with latch and output enable and a drive stage with a transistor feedig a triac, with resitors having high enough value to ensure that the shift registers would survive if a triac would fail and send mains power down to the gate signal. The transistor buffers also ensured that the triacs would never trigger unless supply voltage were over 2V, which is the point where 74HC logic has a guaranteed function. That way we got rid of the classic problem of triacs triggering once when power is applied, causing unneccesary current rush on the mains. The output enable were gated by a reset circuit so the logic wouldn’t output anything until enough time had pased to be sure that the micro controller had loaded reasonable values in the shift registers. To speed up the turn-on time on standard light bulbs, we fed them a pre heat voltage of about 20-30V by rectifiying the mains power, using the triacs as thyristors, and using diodes so each lamp would either be fed mains via a triac or pre heat voltage from a transformer and recifier. All this hardware for feeding 32 lamps, except the microcontroller, fit in one 160x100mm pcb. So in all each 8×8 box had two of those pcbs and a smaller for the microcontroller and a small power supply for the microcontroller. With the pre heat and optimized microcontroller code we actually had to put in a delay in the control software on the Amiga to make sure all boxes had about the same turn on/off time.

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  2. Dave Philipsen

    Allen, I’ve worked with show control over the years but I’d never trust running a system under Windows because of its instability and non real-time nature. A number of years ago I designed a DMX card that plugged into an 8-bit ISA slot. It would continue transmitting the DMX signal even if the operating system crashed. So you could actually reboot the computer without shutting the lights down. The control software I wrote was compiled in C and ran under DOS. A newer project I’m working on now is actually 6809-based running on proprietary hardware.

    In my opinion the show control field has become overly complicated in recent years adopting newer technology that probably has no business being in show control.

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    1. Allen Huffman Post author

      WEIGL and other companies make standalone boxes that you can export the VenueMagic show to, but they can’t handle the scripting and multi sound cards like the PC did. Sign. I’m hoping to replicate some of what the PC did using a stack of triggered sound players.

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