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I decided fairly early on that Iíd put a computer inside the console pillar and arrange that the switches would somehow connect to it, so that I could get the computer to do interesting things with sounds and lights.

Iíve found though that the crank assembly for the time rotor needs to be central in the pillar and thereís no room in there for a PC case as well.

Instead I put the PC case under the sensor panel by cutting the case down using tin snips. I mounted case fans under the speaker rectangle and in the base of the console to get good airflow to stop the PC from overheating.

Digital I/O

So how does one get a PC connected to dozens of knobs and switches? I had thought about dismantling a keyboard and also actually built some circuit boards with TTL IC logic to multiplex the switches over the parallel port. Unfortunately I couldnít resolve the analogue problems with electric fields that scrambled the signals.

So I bought some Digital IO devices from Sealevel Systems. They have one with 96 I/O pins that connects to the PC using a USB connector. They also have a reasonable software development kit (SDK) so you can interface to it using Visual C++ or Visual Basic. Everything else is done with CAT-5 cable and terminal blocks (also from Sealevel systems). The switches just short the inputs to ground as TTL inputs tend to float high. The TTL outputs can drive LED lights or small PC relays which run on 5 volts and 20 mA. These relays can then be used to switch larger currents. I used 12V bulbs for some lights.

There are two hooded displays on the drive panel, a large one on the navigation panel (with the joystick) and another (to be) on the computer panel in the raised black mounting. That's four! Fortunately these days it's easy to attach four displays to a PC. I bought two dual display video cards and configured them to make one big virtual desktop of all four displays, strung out in a line. The software puts up custom graphics behind each display so that the displays show something that looks reasonably Gallifreian.


Each of the 6 raised rectangles on each of the panels has a loudspeaker mounted behind it. I bought a couple of (different) sound cards to drive these, one with support for 4 speakers. Using pan and fade in DirectSound I can control each of these speakers independently for sound effects. I've wanted many more sounds than I could find reasonable samples for from the show, so I've improvised with a lot of other suitable sound clips collected from all over the web. Now every knob and switch makes some kind of blip or warble, and many of them have some practical function.

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