On Sun, 1 Feb 1998 17:52:05 -0000 Andy Shaw writes: >Hi Folks, >I've just observed rather strange behavior that maybe one of you can >help > Well the odd thing is that I noticed that if I >powered >up the receiver and PIC before turning on the transmitter I got all >sorts of >glitches on other chans on the receiver. Not really surprising. Also >these >glitches are much worse with the PIC running than with just the >receiver >turned on. Again not that surprising (but a pain because I guess this >means >that the PIC is generating interference for the RC receiver - sigh). The output of a FM reciever is undefined when no radio carrier is received. Most receivers output white noise. The pulse demultiplexing logic in the receiver may try to reject it, but usually not. Your PIC circuit is working like a very weak transmitter, and giving the output some regular pattern which is interpreted as a legitimate transmitted signal. Signals and noise from other places could do the same thing. The key is that the signal from the transmitter will be stronger than any of them, so the receiver will "capture" the transmitter signal and ignore the rest. To tell if this is a major problem, test the maximum distance that the transmitter can be moved away before control is lost (Put the transmitter antenna down, making the transmitter much weaker than normal, so it isn't too far to see). If it is significantly less with the PIC circuit connected, then there could be a problem. Operate the PIC circuit through all its modes, not just idle. >Oh and can anyone offer any advice on the best way to isolate PIC >based >projects that are used with RC equipment (given that they probably >need to >share a power supply and take input(s) from the RC gear)? As a common-sense measure, keep the antenna and the reciever as far from the PIC as posible. If noise is still limiting the range, put the PIC circuit in a closed metal box, and use ferrite beads and feed-thru capacitors to filter the power and signal lines going in and out. I doubt this would be needed often. The typical RC model has significant noise from the DC motors in the servos and drivetrain that would I think overwhelm noise from a PIC. Also the model is usually operated much, much, closer to the transmitter than the maximum range. _____________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com Or call Juno at (800) 654-JUNO [654-5866]