View Full Version : Interlock and "kill switch" circuit descriptions...?

03-27-2008, 10:22
For those of you who are using the ILDA interlock lines, and / or some sort of remote "kill switch" for your projectors -

Would you mind posting a brief description of the circuits you're using? Not looking for an ultra-detailed schematic or anything like that - just trying to get an idea what you're enabling or disabling (laser power, modulation, shutter, etc.) by using these circuits.



03-27-2008, 12:07
Hey Randy -

So my circuit is built to be redundant. When I plug in my projector only one power supply receives power. This is the 5/12v power supply that controls everything.

This feeds power to an LED to indicate the wall outlet is giving power and feeds power to the power keyswitch.

When they key switch is in the on position power is fed to a SSR that is made to handle 30 amps (overkill). The power from the SSR goes to a power distribution rail where it is distributed throughout the projector.

The interlock is built into this system. When an interlock fails it kills the 5v power and thus the 120v from the distribution to the entire projector dousing all lasers and shutters. I am now at the final stages of developing the circuitry. But if you want I can take a picture of the underside of my projector and post it later.


03-27-2008, 12:27
Here's how I have my projector wired: SW1 is the main keyswitch. SW2 is the "Scram" switch, and SW3 is the reset switch. (Drawing is simplified for clarity; there are other switches and indicator lights that are not shown. They don't change the circuit though.)

By running the power for the hold-in coil on the relay through one of the contacts on the relay itself, you ensure that even a momentary loss of continuity will completely kill the circuit. You have to push the reset switch in order to re-energize the relay. Even if you close the Emergency stop switch again, the projector won't power back up until you hit the reset switch. (Only have to touch it for a moment. One the relay pulls in it has a path to ground to hold itself in.)

Only drawback with this circuit is that if you're running a very long ilda cable (like 100 ft or more), then you might have enough voltage drop in the cable such that the relay won't pull in. I haven't had any problems when using up to 50 ft of cable, but this could be a problem if you go with really long runs. Of course, you'll also have signal loss issues at that point...

Edit: Max, you beat me to it! Was fooling around with the circuit drawing program (Designworks Express) trying to get the labels right, and finally gave up and added them in Paint Shop Pro. Guess it took longer than I had realized...


03-27-2008, 13:46
The picture I have attached is taken with my cell phone. This is the underside of my projector's beam table. In fact I am working on it right now and making a few changes. By the end of the night tonight I should have a working RGY again! This time with ~1400mw :D

Soon it will be an RGY at about 2200mw (532/650/635) once the 660/635nm dichro group buy happens.

Then I just need to be able to afford a suitable blue laser to accompany it all haha. Sorry I am stealing your thread I'm just really excited.

03-27-2008, 15:04
Great ideas - thanks, dudes!

03-28-2008, 12:48
Great ideas - thanks, dudes!

Electronic Goldmine is selling the "A126" keyswitches the CDRH likes (and used by ALC, omnichrome, ILC, a lot of medical ,some coherent" for 1.49.

Steve Roberts