Addict sa RC

Jesse, would you happen to know when and why I should change the power cap that came with the TC2. I read somewhere that it should be changed after 50 or so runs but does not mention why. Hope you could help.

Pit Crew

Jesse T,

Don't forget that High end home audio is going up to 100kHz.
So the answer is yes, I have seen high frequency crossovers. And there are speakers that can reproduce those frequencies. Not that anyone can really hear that high.

But, I think you are right about the impedance.

ESC's are working inside of the audible range as well, that is why when you use a small amount of throttle, you can here that high pitched noise comming from the motor. It won't do that with a MSC. And, it works like AM, amplitude modulation. As you increase throttle, the amplitude of the pulse increases, not the frequency.

Your right though. Good luck finding a ceramic cap with that kind of capacitance.

Stevie

!!Thanx for all the help!!
Stevie

rough512

iTrader: (12)

I beg to disagree,

Operating the ESC in AM would mean series-dissipative operation. Excess voltage would have to be dissipated as heat. Heat requires bigger heatsink. Add to that very poor efficiency.

ESCs work by Pulse Width Modulation. The frequency is fixed at any given time. Power is controlled by varying the Duty Cycle of the pulse. As you increase the throttle, the longer is the ON period compared to OFF period. At full throttle, the ON period is at around 100%. Since the transistors are either ON (zero voltage drop) or OFF (Zero Current), very little power is lost as heat.

JesseT

Pit Crew:
Don't forget that the waveform of the current is square-wave. Square-wave not being a sinusoidal signal consists of the base frequency (which is in the audible range) and of its integer multiples. So if a ESC operates with lets say 10 kHz it is NOT enough that the capacitor operates at 10 kHz.

Addict sa RC:
Electrolytic capacitors do age rather fast but that sounds like a really small amount (50 runs). I think a year is OK.

Pit Crew

You are both correct. I didn't mean that esc's work in am, rather that the frequency stays the same. Where as fm, the frequency changes.

This is a good thread!

madweazl

iTrader: (12)

I just wanted to make a few comments here. First off high end audio does nothing at 100khz, thats just insane. The typical audible frequency range is from 20-20khz, some can hear more or less of this range. Higher frequencies are extremely tough on the ears. I find it hard to believe that there is a driver capable of reproducing a frequency above 30khz with any amount of volume what so ever. Not that any of this matters though, lol. We are talking about speed controls.

I've played with this in the past and couldnt really tell a difference and I'm a pretty good and experienced driver, though mostly offroad you still learn how to feel your car do anything. Has anyone actually noticed there speed control getting how? Hell, with 10 doubles that I used to run on an extremely hot day the fets would be warm at best with a good amount of on/off power and braking. I dont think anyone would gain an advantage unless you were a top level driver and even then I've heard some of them dont use them.

I guess any advantage is good but I dont bother with most stuff like that, my worst finish ever was a 5th in the A when I first started running the TA01 chassis. Worst offroad finish was a 5th at the Ranch Red 100 (anyone remember those?). Granted these werent BIG races but hell, I can drive pretty well. Nitro touring was a different story lol, many DNFs in early days, my little CV just ran hot or not at all Thank god for Rossi!

Pit Crew

Check out Sony's Super Audio C D (SACD) It goes up to 100kHz. So do their speakers. But it is irrelevant.

JesseT

"...with a good amount of on/off power and braking..." That's the case that shouldn't heat the fets too much. Also the capacitor does absolutely nothing in that case. No effect what so ever when running with on/off power. But you're right, it doesn't change the world if you use it. Check the graphs a couple of pages ago. It only boosts the power (or increases the efficiency) at partial throttle.

marvi

iTrader: (82)

do you guys know if i can use a capacitor on a reversing ESC? its a futaba MC230CR. thanks for any info

Manticore

the power cap affixed at the +ve and -ve of batt tabs i.e. there is no issue about reversing ESC but you cannot use diode for reversing ESC.

TRF512

As long as you connect the electrolytic capacitors on the Battery side of the ESC, there would be no problem.

marvi

iTrader: (82)

thanks one more thing, i cannot directly solder the capacitor leads on the solder posts of the + & - tabs of the ESC (just like in the first generation cyclones.) is it ok if i solder them near the battery connector? or maybe ill just put a jumper wire so i can mount the cap on the chassis.

ausracer

i bought about 7 different caps from the local electronics store and a few i am not sure whether they are any good. some of them have the wire coming out either side not just the one. also while i was there i weighed them, 16v 2200uf weighed 7.2g and 16v 4700 was 13.2g. am i gonna notice much difference in these caps cos i spent lots of $$$ taking off them g's.

Leester

iTrader: (23)

I was looking on the Panasoninc capasitor website with a 50 volt capasitor. Would that work on a Novak GT7? Let me know!

-Lee