capacitater

[Schrott]

I hope I made a real mess out of it, trying to spell it.

I need those things for Speed 600 motors. I stoped by the Radio Shack, they have plenty, plate, ceramic or what ever.

What type should I get and how strong.

What is the differance between 2, from each conector to the motor can and the set up that has a additional between the conector

Thanks

gue

[nick_75au]

Hi Shrott,
ceramic disc capacitors are the type you need 0.01 micro farad. one on each of the motor terminals to anywhere on the metal case and one in between the two motor terminals.
The three capacitors work a little better in suppressing interference.
Some recommend a 0.047 micro farad between the terminals, I'm not sure it makes any difference.

Nick

[mfr02]

The really important one is the one across the motor terminals, within limits, value is not critical, type is. The values suggested by Nick are fairly universal, and the picture shows a good arrangement, with the wires kept as short as practical. Note that the power wires to the motor are twisted. This helps minimise interference as well.

[Schrott]

Thanks guys, and now I even know how to spell it.

dis is de place to go to ask a question and get a good answer.

[Kmot]

ceramic disc capacitors
Yeah, what he said!

I once killed a motor and an ESC, thinking that "bigger is better".

It was an expensive mistake. :o

[Schrott]

Kmot, I highly recomened for barbeque dead animal, ground up or just sliced up, motors and esc are not good for barbeque, tough to cut, to marinate and than to shew.

[boater_dave]

Kmot, do you know if the cap really was the reason the motor and ESC is dead? I wouldn't think the value alone would be the reason. My friend has a huge one built into his ESC from Astro (factory installed).
Any EE's out there want to dish on the pros and cons?

Dave

[nick_75au]

ESCs will have caps on the input(battery) side to take the high current pulse drawn from the battery as the ESC switches, once the initial pulse is taken by the cap the battery continues to supply the rest of the switched on time of the ESC and recharges the cap until the next "on time". This happens at the switching frequency of the ESC so thousands of times per second in a Hi frequency ESC.

Put simply it helps to provide filtered power to the ESC

I hope I make sense? :o
Nick

[mfr02]

As the current to the motor switches on and off, the magnetic field in the motor coils strengthens and weakens, This interacts with the coils, producing lots of voltage, but for a very short time. It looks like a spike on a scope. The capacitor acts as a short circuit to this sudden rise, soaking it up. The sudden spikes can, if left to themselves, can transmit radio frequencies via the motor cable, and/or apply large voltages to the output of the ESC. This rarely benefits the ESC. At worse, it will die soon. Possibly, the stray voltages will cause the output transistors to trigger randomly, giving strange and unpredictable responses from the motor. And so on.

[Shaun Hendricks]

Capacitors store current. If you use too large of one, over time, it can build up to a destructive level of feed back current if the ESC is not protected by large enough steering diodes. Remember, the motor is a load, not a power source. It's not expecting much feedback from it power wise.

Some large capacitors can be mounted on the batter side of the ESC to act as a 'surge' current provider for a sudden boost of power, but their effectiveness is debateable at best. They will drain a connected battery pack eventually.

[nick_75au]

Yes , killed my first Lipo that I left on an esc. 3 days and I had a balloon, Doh.
Nick

[mfr02]

There are several types of capacitor. The types normally used for suppression are very small value high voltage types. Effectively, as far passing current at a level that will discharge a battery is concerned, they are two totally separate pieces of wire, and, unless broken, pass no current. Some FE boats, not needing reverse, have an electrolytic capacitor across the motor. These are better at calming the sudden response of the motor rather than preventing RF interference. They are also useful across power supplies to prevent sudden small fluctuations that can confuse ESCs and servos. They often are a bit leaky, because of their construction, and if across the power supply can give a small but constant power drain which will sooner or later flatten the battery.