Installing Motor Capacitors

[Robb]

Although many of us have experience with RCs outside of crawlers, and are aware of how capacitors are needed on typical RC motors in most other realms of RC, the topic seems to be popping up now and then, so I thought I would start this thread for a few reasons. 1) as crawlers become more and more popular, a younger generation is experiencing RC for the first time through crawlers, and 2) as different turn motors are becoming more popular, motor capacitors may or may not be needed on many crawlers...............and 3) I got glitching, so I might as well take pics of how I am trying to fix it.

To start; the purpose of motor capacitors. The caps act as a source of "absorption" of electrical interference created by the motor(s) current pull (or EMF if you watch Ghost Hunters). Without a means of absorption, electrical "noise" can find it's way into your tx/rx signal, which causes radio interruption, which usually shows it's face as "glitching." Now, a couple of years ago, the most commonly used motor in crawlers (as it was the most easily obtainable high turn "5XX" motor) was the 55T "lathe" motor. 55 turn or higher motors typically don't pull enough amps to create enough electrical interference to affect a typical radio signal, so motor caps were/aren't used all that much in crawlers. BUT, as lower turn motors become more popular due to the ever increasing number of transmissions (and gear ratios), many crawler motors out there could probably use motor caps as insurance against radio glitching.

Just my opinion, but if your rig requires a 55 turn, or higher turn, motor, then you probably won't benefit from motor caps. But if you are running a lower turn motor, caps could benefit you, and definitely won't hurt you. Even if running a high turn motor, installing caps is so easy and cheap.............you might as well.

The most commonly used (probably because most commonly available) capacitor type/size is the ceramic disc .047mF capacitor. These are easily available at your local Radio Shack for about $1.50 for a pack of two. The all-around best method is to use three caps per motor. For a single motor rig, we are talking a total investment of $3, and for a two motor rig, a big 'ol $4.50.



Take three of the capacitors, and twist the leads into a triangle pattern.



You want to end up with a cap between the + and - tabs, a cap between the + tab and the case, and a cap between the - tab and the case. Most motors you will work with, will have a center lug tab between the + and - plates on the endbell end of the motor. This tab has the same electrical potential as the outer motor case, so you can use it as the third contact point. If your particular motor does not have this center tab, simple sand the surface of the outer casing of the motor between the plates, and solder to that point on the case.

A pic of the mock up.



From here, just heat the tabs and add a little solder to all three points.



Place a couple of short pieces of heatshrink on your motor wires, tin your motor wires, then solder your motor wires to your motor tabs. When cooled, heat your heatshrink over the tabs. Then trim the excess cap leads from the back of the motor tabs. Then "bend" the remaining cap leads so that they are as out of the way as possible.



Then install motor on rig.




Just because the glitching I am getting is pissing me off, I am, from now on, just going to install caps on all my RC motors, even if they are high turn crawler motors, and probably not needed. For just a few bucks, and five minutes, they are well worth having there for insurance against radio interference.

[jmizoguchi]

nicely done

[Rockit1973]

COOL! This was one of those things I was wondering about!!!!

Great info.
Thank you.

[Philistine]

Great write up! I wish someone had posted something like this before I tried putting my caps on my motor. It was a fustrating bit of trial and error. Your set up looks so good I might just buy new caps and reinstall them.

[JohnRobHolmes]

Very good writup there, and that is certainly the most common cap used for EMF suppression on motors.

[4xFord]

Hey JRH can you add this to the sticky at the top?

[Philistine]

Originally Posted by JohnRobHolmes

Very good writup there, and that is certainly the most common cap used for EMF suppression on motors.

While it is the most common, is it the best? Are there better capacitors for specific motors?

[Philistine]

Originally Posted by 4xFord

Hey JRH can you add this to the sticky at the top?

X2

[Miller Time]

Originally Posted by Philistine

While it is the most common, is it the best? Are there better capacitors for specific motors?

They should work fine for any motor you would use in an RC.

[JohnRobHolmes]

The important matter is that the capacitors are ceramic, and of high enough voltage. The capacitance can be anywhere from .001uf to .47uf generally. Motor size doesn't matter.

added to the motor sticky

[Teto]

good write up !
my brothers Axial AX-10 Scorpion "glitches" all the time he has upgraded the motor i'm not sure what turn it is. but i'm gonna try this and see if it helps him. if it works it will be great but if it doesn't help ill know its a cheap way to find out that its not the motor

[smokediver]

ok maybe a noob question I don't know. Are caps needed if running 2.4 radio gear?

[killswitch]

Ive seen 2.4 systems glitch with no motor caps.

[EddieO]

With the radios now a days, typically a motor will only interfere on something that is already screwed up......so the caps are a bandaid.

Chris Tosolini's Ti based mod we won snowbirds with in 1/12th scale had no caps installed.

There is no need to really solder them to the can like that anymore.....just two caps across the tabs to the central area on most motors. Most of the new motors like the Orion V2 or the Checkpoint already have them installed....

Later EddieO

[smokediver]

thanks

[airdreams1]

I have a novak esc & it sais in the instructions to remove the caps on all reversable esc's. they clame they can fry your esc. So i removed them from my motor.
So i guess Im lost on this one... Id think the guys @ Novak know what they are talking about, but we all know what asuming gets us.

[Thorsteenster]

With 2.4Ghz radios on the market, you don't need caps with these as they don't pick up on the e-noise.
One thing a little confusing with that about the Novak ESC's, many motors today come preinstalled with surface mount caps which I don't know if they are removable.

[JohnRobHolmes]

Originally Posted by airdreams1

I have a novak esc & it sais in the instructions to remove the caps on all reversable esc's. they clame they can fry your esc. So i removed them from my motor.
So i guess Im lost on this one... Id think the guys @ Novak know what they are talking about, but we all know what asuming gets us.

You are referring to the Diode. Reversing ESCs don't use diodes, but forward only use them to reduce the chance of blowing FETs. Either novak has a typo, or you have your terms confused.

[billybob_81067]

I know this thread is old, but I figured I'd let you know that I ordered a hundred .047uf 50volt ceramic caps from mouser for a whopping 4.90 plus like 7 bucks shipping. I don't care how many motors I swap out I'll never use em all! Lol.

[rick_c]

Thats some pretty interesting stuff. I even pasted it into a word doc for future reference.