Hands On Interactive

PIX Multimedia Presentation Controller
PIX front panel
  Controls a theatrical presentation, with built in video and audio faders, DMX lighting control, stage pyrotechnic outputs and relay controls for curtains etc. All of this is under computer control.

We were commissioned by the DRP Group to design and build this unit. It was sponsored by the DTI under the Smart Award scheme. What does PIX stand for? It's not short for Pictures even though it can handle video and cross fade between video channels. It's the interface between a computer and a stage presentation. It's aimed at any job that has a variety of multimedia devices that need to be coordinated. It's primary role is in theatre but any automated presentation can benefit from it. 

Just imagine this as your show control system. It can handle a whole lot of tricky tasks that would normally take a rack full of multimedia devices. PIX can automate and can act as the audio mixer, vision mixer, lighting control, pyrotechnic firing control, curtain control and switch other A/C devices, all under computer control.

It can do...

  • Cross fade between video channels.
  • Mix and fade between audio channels
  • Talk to lighting systems using DMX
  • Curtain control
  • Switched A/C power.
  • Pyrotechnic outputs for theatrical bangs and flashes.

It is controlled from a computer via a serial port.

Only the power and pyrotechnic controls are available from the front panel. Everything else is controlled by a computer. The pyrotechnics are signalled using LEDs but are not actually fired. For safety reasons, the pyrotechnics are only fired by a manual keyswitch.
The view from the back showing all the connectors. Everything is isolated to avoid crosstalk and noise problems. 
  This is the open chassis being tested before dispatch.
  The microcontroller at the heart of this design is buzzing away with the amount of work it has to do. There are a lot of ports for it to look after, and timers to keep things running sweet. As you can see, every available bit of spare copper has been incorporated into a ground plane to minimise electrical noise.

For those of you who like facts and figures:

PIX General Specification

Audio Frequency response 20Hz - 20kHz, gain fixed at 0dB


7 Right and 7 Left channels
Input impedance  18kohm balanced
Input clip  +10dBU (0dBU = .775V rms)
Attenuation  0dB - 63dB in 1dB increments
14 Connectors 3 pin 6.3mm jack socket (ground switched inputs)


1 Left and 1 Right channel
Output impedance 60ohm balanced
Attenuation  0dB - 63dB in 1dB increments
2 Connectors 3 pin 6.3mm jack socket 

Video PAL Composite Video
Bandwidth 5MHz
Gain 0dB


2 Channels
Input impedance  75ohm
Cross-fade attenuation/resolution  255 linear steps
2 Connectors  75ohm BNC


1 Channel
Output impedance  75ohm
1 Connector 75ohm BNC

Lighting DMX512 conforming to USITT DMX512/1990 (4uSec)
Physical Layer
Data rate  250k baud
Electrical spec  EIA -485


36 Serial channels (0Hex to 23Hex)
Output impedance  120ohm
Resolution 255 linear steps
1 Connector  5 pin XLR

Pyrotechnics Relay output
Volt-free contacts
Maximum Current 2A
Manual switch in-line with output, with tell-back facility for PIX


6 Channels
6 Connectors 2 pin male Series 680
6 Push button switches for arming and a master firing keyswitch.

Curtain control Switched mains fused output
Maximum Current 1.5A
Fuse Rating 1.5A antisurge

Controlled AC Output 2 Channels
2 Connectors IEC female

Central control RS232C using proprietary protocol


1 Channel
1 Connector 15 Pin D-Type female

Enclosure 19 in 3U case universal desktop or rack mounting enclosure

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Last Update 14/11/01