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Basic understanding of ESC

Posted by Tim Michals on December 21, 2009 at 6:19am
I'm trying to find out what is the maximum update rate for a typical ESC is. I saw that most quad copter designed require the ESC update rate to be very high, i.e 100Hz or more.My understanding a ESC takes a PPM signal from 1ms to 2ms with a 20ms duty cycle. So a max of 50Hz update rate, is that correct? Is there some "play" in the duty cycle maybe max of 10ms. Or I'm way off base? Looking at ESC data sheets seem to be missing this information.
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Comments

  • Tim Michals December 22, 2009 at 7:23am
    thank you, a lot of good stuff here...
  • Dror Caspi December 22, 2009 at 6:21am
    It's all there, look at the schematics in the hardware folder
  • Tim Michals December 22, 2009 at 6:15am
    I saw your web page for your quad, could you share a parts list?
  • Dror Caspi December 22, 2009 at 2:11am
    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.
  • Xander December 22, 2009 at 12:06am
    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?
  • Dror Caspi December 21, 2009 at 9:25pm
    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
  • Tim Michals December 21, 2009 at 3:16pm
    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...
  • Xander December 21, 2009 at 3:14pm
    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.
  • Tim Michals December 21, 2009 at 2:16pm
    Even if you change the ESC at 100Hz can the motor see that change that quickly?
  • Xander December 21, 2009 at 1:29pm
    At 500Hz 2ms pulses will blend into a steady signal. Never tried it, but it seems like that would confuse the esc.
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