Technical, Techniques, Hints, and Tips > Radio Equipment

rudder interference

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tidtug:
I have just put the radio bits in a small lesro TID Tug, Sea hunter 25a speed controller (Yes I know over the top!), Jeti rex 5+ receiver,Sanwa 102 servo, running on 6 volt nimh battery and bec - think thats all thats relevant?
When the motor isn't running or I run the motor on slow it's fine, as i speed up the rudder servo twitches and at one point locks hard right, eventually the motor doesn't run smooth but 'hunts'
The motor isn't supressed, but if run direct from another battery, with the rest of the radio working, there is just a minute amount of flutter on the servo, I do mean minute which I could live with.
Any ideas?  ???
All help most welcome.

towboatjoe:
Do you have RF noise supression capacitors on your motor leads?

Motors create RF (radio frequency) noise that can interfere with your radio signal. The best way to keep RF problems at a minimum is to solder a .01uF (micro-farad) capacitor onto each motor lead then onto the casing of the motor. To further dampen RF noise, solder a .047uF capacitor across the two motor leads. The best way to get the capacitor leads to adhere to the motor casing is to rough up the casing a little with a cut off disk in a moto-tool and put some rosin on it before soldering. Brushless motors do not require suppression capacitors.

Doc:
Doing all the 'normal' RF interference thingys, like twisting the servo leads, adding ferrite 'beads' to the leads, seperating the electrical and electronic wiring as much as possible, and adding a grounding jumper to the stuffing box also can help.
Capacitors work very well for DC RF interference suppresion.  To a point, larger is better.  That 'point' being mainly when they get to be to @#$ big to fit in the hull, and that is an exageration, but not much of one.
If you can't suppress it, then shield it.  Simple idea but not very easy when you try to make it practical.  About the only thing that doesn't benifit from being 'shielded' in a model is the receiver's antenna (aerial as you guys say).  That's another thingy that can be carried way too far, so keep it sort of reasonable (don't ask, I don't know either).
Good luck.
 - 'Doc

dougal99:
Hi Tidtug

I never used to worry about suppressing motors as I'd never had a problem and was lazy :-[. Then I built a small frigate (24 inch) that I powered with two small motors off one battery and the ESC providing a BEC. The interference was horrible. Suppressing the motor cured it all. So give it a try - I found it easier that I had anticipated.

HTH

Cheers

Doug

Fast Electricals:
I think that the problem could be your supply voltage.  Most ESCs are designed for 7.2v operation rather than the 6v on your set up. As the motor loads the battery, the voltage drops below the minimum required by the BEC circuit and this could cause the receiver glitching that you describe. Try a 7.2 v battery.

Neil

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