The connections

In the end, I controlled three aspects of the slide projector from the Arduino board:

1. Moving forward / back slides
2. Turning the lamp on and off
3. Rotating the lazy Susan

To move the slides forward / back, I replaced the wired remote control connector with connections to relays (it was a standard 6 pin DIN connector) - I left it on for 0.5 sec, then waited 1.5 seconds before pressing it again.

To turn the lamp on and off, there is a special connector on the side. I have never seen something like it, and couldn't find a replacement plug. So I drilled a hole in the side to pull out the two wires that were soldered together inside. Apparently when people did presentations with multiple slide projectors, this connector was used to fade between projectors, etc. Ah, those were the days. I then connected these two wires to a relay. The first one started to smoke - I got a more powerful one (240V, 3A), but after using it for a few minutes it started to smell also so I took it out. I guess the current that is passing through the globe is passing through this connection, so maybe I need one with a higher current rating.

The last two connections out were connected to the motor controller (see previous post). If one is high and the other low, the motor will rotate clockwise, and vice versa for anticlockwise. If I set both to low, then the motor does not move.

For these last three connectors, I used the servo connectors on the demo board, and modified the arduino code to just send digital on or off (as opposed to PWM (pulse-width modulation) which is required for the servos).