Controlling focus on old Kodak Carousel slide projector


I’m trying to have my Arduino control an old Kodak Carousel slide projector. I’ve hacked the remote control, a 5-pin device that advances, reverses, and controls lens focusing. The fwd and rev are simple switches, and I can control them easily. The focus adjust has me-- a total electronics novice-- stumped. The circuit includes a1N4005 diode in this configuration:

I think I understand the idea of the switch: when the focus control on the remote is pressed in one direction, it sends a signal to a solenoid in the projector that fires the focus motor in one direction; when the focus switch is pressed the opposite way, the motor runs in reverse.

My idea was to connect the 3 wires that control focus (yellow (common); black; and brown) via a relay that I control w/ my Arduino. No luck… just a realization that I don’t know what the heck that diode is doing, or how this circuit works.

I’d be mighty grateful if you had any suggestions.

Many thanks.

I am not sure about that diagram or what the schematic means. My best guess is that focusing can only happen when brown is connected to yellow; then black can be connected to brown, and the diode controls the direction of current flow to cause the motor to rotate one way or another. But I am not really sure - that is a very odd diagram.

What you might try is to reverse engineer what the pins are doing (using a meter) when you press buttons or such on the remote (assuming you have it). Then replicate that using relays. If you do have the remote - make sure on where the location of that diode is - whether it is in the projector - or in the remote. Most likely it is on the projector, though.

Thank you for the response. Much obliged.

A kind person on another forum wrote this:

"Looks like the focus motor runs on 24V DC and the 1N4005 provides half wave rectification from the 24V AC. When connected in one direction, +24V rectified is supplied to the focus motor and it rotates in one direction; when the remote control switch operates in the other direction, -24V AC is supplied to the focus motor and it rotates in the opposite direction.

So your relay connection will have to have 3 modes. (1) no power - focus motor doesn’t rotate. (2) +24V DC and (3) -24V AC. Probably best done with 2 relays. One to disconnect focus motor from power. Second relay to reverse the diode polarity."

…I’m afraid I don’t understand the electronics (half wave rectification? pos. vs. neg. voltage?). As a practical matter, though, I have a 2 relay module that’s Arduino controllable, but I’m not clear what the wiring would look like. Any suggestions would be much appreciated. Meanwhile, I’m off to fiddle with my relays & wires and will report back if I figure things out.


For anyone else who might like to look at the wiring diagram, my Kodak link up above just goes to the whole PDF. The actual schematic is on Page 43 of the PDF.

Having looked at the circuit diagram it does look like gibberish. However, the slide change motor works on AC or DC, I forget which, Then a diode is used to inject DC into the motor ti immediately stop it. I know because my projector would not stop changing the slide. This diode is buried in some sleeving leading from a dropper resistor