Comment by Jack Crossfire on December 21, 2009 at 11:03am

The source code for bl-ctrl is an excellent review of ESC design. The update rate of an ESC is over 20khz, high enough for humans to not hear. The communication protocol is 200Hz - 1khz.

Comment by Xander on December 21, 2009 at 11:23am

I think with at least some ESCs speeding up the communications to 100Hz doesnt cause any problems. Some quads insist on using special ESCs that can handle much higher rates, but the benefits are questionable. There's momentum involved in actually changing the speed of the motor. At some point you're updating the ESC faster than the motor can keep up.

Comment by Dror Caspi on December 21, 2009 at 12:42pm

Some ESC's can accept up to almost 500Hz of update rate, i.e., they only care about the pulse width and not the cycle. Turnigy Sentry is one example.

Dror

Comment by Xander on December 21, 2009 at 2:29pm

At 500Hz 2ms pulses will blend into a steady signal. Never tried it, but it seems like that would confuse the esc.

Comment by Tim Michals on December 21, 2009 at 3:16pm

Even if you change the ESC at 100Hz can the motor see that change that quickly?

Comment by Xander on December 21, 2009 at 4:14pm

It's hard to say. Not an easy thing to test. Probably depends on the motor (torque and mass), as well as what it's attached to. Anecdotally, seems like 100hz helps with a quad. More than that is debatable. Some people do claim they get a lot more out of their fancy 1khz escs. For me, not worth the extra money, at least for now. You can certainly get a flying quad with 100hz, probably even 50hz.

If we're talking about anything other than a quad, you probably dont need anywhere near this level of control.

Comment by Tim Michals on December 21, 2009 at 4:16pm

Yes, this a quad. I'm waiting on new micro controller LPC2148 board... for a first pass, then a PIC32, a new version is coming from sparkfun with 512K flash and 128k of RAM...

Comment by Dror Caspi on December 21, 2009 at 10:25pm

I wrote "alomost 500 Hz" and I meant exactly that, it's actually around 490 Hz. I use pulse widths of 0.8 to 1.8 msec (I set up the ESC for that).

Dror

Comment by Xander on December 22, 2009 at 1:06am

Hm, ok, impressive. Guess I just assumed they werent that sensitive. When you say "set up" you mean with one of those ESC programmer cards?

Comment by Dror Caspi on December 22, 2009 at 3:11am

Yes, you can set the minimum and maximum throttle with the programming card or with the interactive setup, I don't remember the procedure since I did it long ago.

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