I'm working on a project for work right now (performing arts theatre) and seem to have run into some trouble. I'm tying some of our older work light system into the DMX lines. The part I'm stuck on is as follows:
Latching relays in a breaker box provide their own 12VAC
Buttons in the control panels have two diodes, one in each direction
Momentary buttons connect cause +12VDC or -12VDC back to the relay
I'd like to send +5VDC from an arduino pin to turn the relay on or off
I'd like to avoid using a relay
So far I've tried everything I can think to try with both a breadboard and electronics emulation software. Including SCRs, transistors, and every combination thereof. Any suggestions?
USE a Relay... what you are trying to do is kinda dangerous, especially to an Arduino. What you describe sounds like a bi-polar latching relay. One diode sends a positive voltage to one coil and the other does the opposite to another coil in the relay. There are also single coil latching relays. Set the polarity in one direction and the relay pulls in, reverse it and the relay drops out. 2 control leads and a common means a 2 coil relay and one wire and a common means a single coil relay. The control methods I mentioned are the most common but by all means not the only methods. It is always best to mimic the action of the control switching, the alternative is to re-engineer it.
The possibilities are high current or high voltage or something that isn't ground referenced. The simplest method is to add a pair of relays contacts across the switch contacts. This way you have no modifications to the original control electronics except remoting the controls to another location. and you have 100% isolation from the lighting control circuirty.
There is one other consideration here and that is any applicable wiring code guides. You Must follow Code or be liable for any results of your modifications.
Thanks for the input. Originally I had thought it was a double coil relay but once I learned it wasn't I was hoping to figure out something the cheap. Relays it is then I suppose. Thanks for the insight!
Probably (a supposition) the current isn't real high and a small relay might well suffice. The actual control functions might be done with a triac optocontroller a MOC4031 is one example. Google "Triac Optoisolators" and you will have all the information you will need. My relay was based on the safest wired method possible. I once saw a pinball flipper solenoid used, one for on and one for off these devices actually pushed the buttons. The guy made a box to fit over the switch box with two solenoids mounted on the side of the box, when he dropped the box on the switch box it pushed the buttons.,..
Here is link to an article I found in my Google search, It's from this forum. http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?action=print;num=1276640390
