Controlling relay with radio

[Stratotanker]

I am wanting to know how hard it would be to trigger a relay that is tied into a radio system, My main question is how would the signal wire trip the relay on or off, I am just needing the relay to cut power to certain onboard components??? Is this going to require a complex circut board and would there be a differance in PPM vs PCM?, I am hoping for a super simple setup as my little gadget will be a safety relay so it needs to be simple and reliable. Thanks in advance.

Chris

[Andy W]

Search for posts on using lights (LED's) on models (in this forum)..
You need a circuit that senses the signal from the Rx, and turns on or off based on pulse width (servo "position")..
..a

[vintage1]

Easiest way is to get a 5v relay, rip a duff servo apart, stick a diode in series wih the relay and put it where the servo motor was.
The servo wil try and 'drive' the relay to get to where the pot is. Any stick position one way from that will pull the relay in, the other way it will find the diode blocking current, and the relay will drop out.

[Eric Brouwer]

Easiest way is to get a 5v relay, rip a duff servo apart, stick a diode in series wih the relay and put it where the servo motor was.
The servo wil try and 'drive' the relay to get to where the pot is. Any stick position one way from that will pull the relay in, the other way it will find the diode blocking current, and the relay will drop out.

Great idea. Neer thought of such a simple R/C switch.

[flflyer]

check this site. It has a couple of r/c switch's as well as a bunch of other r/c related circuits.
http://www.uoguelph.ca/~antoon/gadgets/gadgets.htm

[Miami Mike]

Easiest way is to get a 5v relay, rip a duff servo apart, stick a diode in series wih the relay and put it where the servo motor was.
The servo wil try and 'drive' the relay to get to where the pot is. Any stick position one way from that will pull the relay in, the other way it will find the diode blocking current, and the relay will drop out.We discussed some similar ideas recently in this thread (http://www.rcgroups.com/forums/showthread.php?t=333017). For example, if you like spending money instead of modifying a servo, there's this gadget (http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCJD6&P=0) from Futaba.

If you want to use the PCB from a stripped servo, my suggestion is to use two equal resistors as a voltage divider in place of the potentiometer. For the relay, I don't see any need for a series diode if you connect one of the relay coil terminals to ground and the other to either motor terminal, but I've never actually tried it. Is there a reason why it wouldn't work that way? On the other hand, it might be smart to connect a diode across the relay coil instead, to clamp voltage spikes.

Stratotanker, if you supply more details about your project we might be able to come up with something even better for you.