Use of capacitors with motors for ESC

JimmyB

JimmyB

Now retired - trains and fishing
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Reading a manufacturer's instructions I have come across the following information:

Make sure your motor is fitted with two (2) motor capacitors (0.1uF) - one from the negative terminal to the can and one from the positive terminal to the can.

Please can somebody explain this to me, should this be the case for all motors/ESC or just certain ESCs and what are the ramifications of not fitting the capacitors.
 
This is for 'noise' suppression, and with modern electronics (if properly designed) should not be necessary.

There are certain motors that are notoriously noisey, and it may be an idea with those.

Many modern devices have internal oscillators, for various functions, and sometimes electrical noise can be an issue.


In the bad old days, every HO/OO loco needed suppression.

PhilP
 
PhilP said:
In the bad old days, every HO/OO loco needed suppression.

PhilP
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I was always told that this was to stop TV interference ................ rather to stop interfering with the TV :oops:

I think it might be Micro Viper that still suggest the capacitor(s).
 
Rhinochugger said:
I was always told that this was to stop TV interference ................ rather to stop interfering with the TV :oops:

I think it might be Micro Viper that still suggest the capacitor(s).
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Back in the early 1960's I'd come home from school and, after tea, go up to my bedroom to "play" with my Tri-Ang train set. A few weeks after this started next door, whose T.V. aerial was inside their loft, complained that they could no longer enjoy watching Coronation Street!
 
Rhinochugger said:
They didn't miss much :devil::devil:
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Yes I keep on wondering what happened to Ena Sharples and Mini Cordwell if I catch some Corrie on a friends box. But then I am surprised if I see any East Enders and there is no Dirty Den or Ange not to mention Arthur. What happens to these people?
 
dunnyrail said:
Yes I keep on wondering what happened to Ena Sharples and Mini Cordwell if I catch some Corrie on a friends box. But then I am surprised if I see any East Enders and there is no Dirty Den or Ange not to mention Arthur. What happens to these people?
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What about Crossroads?
 
My old Bachmann 2-6-0 "Centenial" had those capacitors, fitted on a ring mount on the motor's end bell used as suppressors, fitted. One day they blew, bringing the loco to a dead stop. I was advised, on here, to ditch them. However, now I am in the process of converting all my Bachmann, and a couple of Accucraft, locos, to RC/Battery power/sound I have noticed a device referred to as a "balun core" always being supplied and detailed to be interposed between the ESC output and motor. I use Fosworks Cobra ESC's exclusively.

This device has both of the ESC's motor output wires wound once, or even twice, through it. It is suggested to be positioned as near to the motor as possible. It's application here, as I understand it, it to minimize the effects of RF noise from the motor on other elements of an RC/Sound/Battery installation. It certainly proved its worth, when suggested by Steve Foster of Fosworks, and introduced into the conversion of my Accucraft K-27. There it appears the "noise" from the loco's motor was causing all sorts of random activation of sounds from the Sierra sound card. A balun core fixed the issues. I now have a stock of balun cores.

Please excuse my in-exactitude in use of terminology here. Max
 
maxi-model said:
My old Bachmann 2-6-0 "Centenial" had those capacitors, fitted on a ring mount on the motor's end bell used as suppressors, fitted. One day they blew, bringing the loco to a dead stop. I was advised, on here, to ditch them. However, now I am in the process of converting all my Bachmann, and a couple of Accucraft, locos, to RC/Battery power/sound I have noticed a device referred to as a "balun core" always being supplied and detailed to be interposed between the ESC output and motor. I use Fosworks Cobra ESC's exclusively.

This device has both of the ESC's motor output wires wound once, or even twice, through it. It is suggested to be positioned as near to the motor as possible. It's application here, as I understand it, it to minimize the effects of RF noise from the motor on other elements of an RC/Sound/Battery installation. It certainly proved its worth, when suggested by Steve Foster of Fosworks, and introduced into the conversion of my Accucraft K-27. There it appears the "noise" from the loco's motor was causing all sorts of random activation of sounds from the Sierra sound card. A balun core fixed the issues. I now have a stock of balun cores.

Please excuse my in-exactitude in use of terminology here. Max
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Max a term I had not come across (just googled it), and it would seem I have used these myself, and my ESC with them do not mention capacitors, however the ESC that says to use capacitors does not seem to have a "balun core", so this could be the solution.
 
Brushed motors do benefit from suppression as close to the motor as possible. Pretty much all ESCs will have suppression, but if your cabling to the motor is longer than a few inches, they are worth fitting.

Make sure the capacitors will handle the voltage - so for a 12V motor, 25V is a good value. They must not be polarised - so avoid electrolytics, but smaller values still work well. 100nF is normally more than enough. You can also fit ferrite beads to the motor wiring if you find that control is not great - as this could be due to interference affecting the control signal. Probably not required with multipole motors and good quality ESCs.
 
balun core? Interesting, we usually call them ferrite cores. Indeed you can use a "balun core" to make something other than an balun (a very specific purpose).

Basically you are making an inductor with a coil of wire, the "core" increases the amount of inductance, just as the metal in a tranformer does (which is 2 coupled inductors).

inductors in series can be used to "block" high frequencies, in this case block the high frequency noise from the brushes making and breaking contact.

capacitors in "parallel" (one end on the noise, the other to ground) can be used to PASS high frequencies (in this case to ground).

By shorting some of the noise to ground, and then using an inductor to block any getting "into" the ESC circuit, you have noise supression.

in fact most filters use a combination of inductors and capacitors.

Unfortunately, some DCC decoders react poorly to this filtering, often interfering with reading BEMF.

Greg
 
It has been my experience when fitting Balun cores in line (as suggested by Steve Foster) that the "noise" suppression does not have very much effect on the range of the 2.4 GHz Deltang DSM2 based R/C.
Hand shielding the Tx handpiece antenna is more deleterious to overall range.
Rather, the suppression seems to aid the filtering and stability of the controlling microprocessor being used by the ESC itself.
In the case of Fosworks COBRA ESC's, performance is excellent.
 
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