Re: receiver question 1b: interference [TANKS]

[Frank Pittelli <frank-at-rctankcombat.com>]

Amir Tahvildaran wrote:
> Hmph, I think I installed the relay diode correctly with your 
> description and this site's diagrams:
> http://www.kpsec.freeuk.com/images/diopro.gif
> http://www.kpsec.freeuk.com/components/diode.htm
> 
> here is the problem relay with the diode installed, white is + relay 
> coil, black is - relay coil:
> http://www.cs.drexel.edu/~adt22/tank/relay_diode.jpg
> does that look right?  I didn't test it reversed because I was pretty 
> sure that (a) it was right (b) it would blow something up if it was wrong.

The diode placement is correct.

> Anyway, when I activate this trigger relay I still get activity on the 
> rotate.  What is *really* bizarre is that when I touch the bare black 
> wire (relay coil), it activates the rotate!  I know that the body has 
> some electrical property, like high capacitance or something - but I 
> still don't understand whats going on...
> 
> Here are two overall shots of this messy circuit:
> http://www.cs.drexel.edu/~adt22/tank/overall_turret_circuit.jpg
> http://www.cs.drexel.edu/~adt22/tank/overall_turret_circuit2.jpg

Based on this description, it's probably a wiring problem, not an RF 
noise problem.  Unfortunately, I'm about to leave for the airport, so I 
can't continue this thread in detail.  But, if you can activate the 
rotate simply by touching the bare ground wire, then I would suspect 
that the transitor shown in the picture has something to do with it. 
That is, it is seeing a little current on it's control side, which is 
allowing a large current on the load side.  What is that FET for?

I would proceed as follows:

1) Disconnect the rotate and trigger circuits from the common bus and 
test each one individually to make sure you have the proper wiring.

2) Use separate batteries for the control and load side of each circuit, 
  with completely separate grounds.  In general, this is a good thing to 
prevent voltage and current spikes on the load side from finding their 
way onto the control side.  It also prevents electrical noise on the 
load side from interferring with the control circuits and eliminates the 
possibility of having the control side completing a circuit involving 
the load.

        Frank P.