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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

[tidtug]

To keep you all up to date! I liked Neils idea best and it was easy to try with a spare transmitter battery! NO CHANGE! I have extracted all the wiring from the hull and seperated it as much as possible and away from the arial but to no improvement also tried cooking foil as a screen (it worked between a TV and Video many years ago). Looks like some capacitors then!!, what would puzzle me here is that if the motor is run from a seperate spare battry I get virtually  no problem!? Can it somehow 'feedback through the speed controller? The tug was built and had the motor in it when I bought it, and had had radio control control fitted so presumably it did work without capacitors, or maybe thats why it was for sale
They will also be a bu***r to fit as the motor is kept in place by a tight plastic housing - stll thats a model boat.
Will keep you informed and THANKS for the advice

[OMK]

Since it's a bit of a "xxxxx" to gain access to your motor, a quick 'n' dirty solution might be this...

Snip the wires that connect to the motor, then insert a 2-way, 15amp connector block (as per the attached sketch). Reconnect both wires and at the same time insert the suppression capacitor. Try to have it that the terminal block / capacitor assembly is as close to the motor as possible.
This is probably not the most elegant method, but it should get you out the poop.

The capacitor, by the way, can be any value between, say, 10nF and 100nF (0.01uF ~ 0.1uF). Just to clarify any confusion, it may have a number printed on the actual body. If it's a 0.01uF cap it will have '103'. If it's a 0.1uF it will have '104'. Be sure that its voltage rating is at least 25%  more than your battery supply.

As an aside, if may prove sagacious to include two more caps' with a value of 0.01uF. Solder the first one between the blue terminal and the actual motor body. Solder the second between the yellow terminal and motor body.
This, however, may be a moot point since you're having trouble getting good access. Fortunately, you may find that just the one cap - as seen in the sketch - will cure the fault.

Good luck.

[Stavros]

Silly thought but are your servos ok had a similar problem with a tug cured it with a new servo,now before you lot jump down my throat for that one but it's true tried old servo in another and guess what same prob.If a servo is faulty it can case a backfeed and generally cause trouble hope this will help Stavros

[Doc]

About the voltage rating of the capacitor(s), make them at least twice the supply voltage.  You might be suprised at the initial surge voltages at times.  Three times the supply voltage certainly won't hurt either.  The voltage rating can't be too high, it can certainly be too low!  If there's any significant difference in cost because of that, I'd find another supplier.

Stavros - Want another one of those qwerky servos?  Just happen to have one you can have...free!

 - 'Doc

[OMK]

He's right.
That "...at least 25% more than your battery supply" is a typo. It's meant to be 250%.
The advice is good. Votages ratings cannot be too high.

Though, I'll bet my winning lottery ticket you haven't tried it yet (if ever).

[Doc]

Good Grief!  If you've got a winning lottory ticket don't bet it on some of the stupid things I have / haven't tried... some I won't admit to.
 - 'Doc

[wombat]

One thing that hasn't been mentioned - make sure that you get ceramic capacitors rather than, say polyester or polycarbonate caps - they will not supress the noise anywhere near as well (if at all).

If it is garbage coming up the lines from the motor, the full monty suppression system I have used in other applications can be tried - Break both lines to the motor, insert in each one a 100uH inductor with a suitable current rating. On each side of the inductor place 100nF ceramics line to line. Also place in 10uF tantalum capacitors if you are running the motor single direction (don't use them if the motor is reversing.)

Tim (the Wombat)

[malcolmfrary]

I agree with all that has been said about fitting capacitors but dont forget to check that the power wiring is in good condition.  A bit of "black wire corrosion" can be a real pig to track down, and can give just the symptoms described.  It introduces a small, but varying resistance in the supply, and this will affect the voltage at the BEC - an additional benefit is that often the resistance will increase as the problem areas temerature increases due to the current load.  As any servo relies on having a stable voltage supply, any variation will cause glitching.  Its difficult to measure as well, mostly because you cant connect a probe from the voltmeter reliably and not disturb the problem.
Been there, been caught, read the book......