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  1. #1
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    Slowest motor speed? What's "idle" speed?

    What's the slowest motor speed you guys get? I'm finishing up my Cyclone build, and everything is working great. I'm pretty sure I've calibrated by ESCs correctly (all those beeps!) but in the Configurator motor test, the slowest setting where I can actually get them to start spinning is around 1100rpm. Is this normal? Is this just the nature of brushless motors? It just seems weird that when I'm testing various commands with my tx, pairs of motors will shut off - for example (X configuration) if I move the pitch stick full up (down), the back motors speed up (as expected) but the front motors shut off all together, they don't "idle" or anything.

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    Senior Pilot wooden's Avatar
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    Yes this is very normal, increase the MinArmedThrottle in the Miscellaneous Configuration page in Configurator until all four motors spin evenly when the copter is armed. This is the minimum allowed PWM pulse.
    push the envelope, watch it bend

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    But, could it be known why it is like that? Couldn't it be lower? I'm curious

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    Moderator AeroQuad Core Software Developer kha's Avatar
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    Quote Originally Posted by FrancoDeGolla View Post
    But, could it be known why it is like that? Couldn't it be lower?
    There is two points there
    - spinning rotors while armed is a very good indication to keep away
    - some ESCs refuse to start again if the motor stops with throttle applied, this happening mid air... you do the math

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    Senior Pilot wooden's Avatar
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    The minimum armed throttle is dependent on your ESCs. They're supposed to work with PWM signals between 1000 and 2000us, but in reality, most work with a smaller range of values. Some of my smaller ESCs don't spin the motors until closer to 1250us, while the rest of them typically turn motors on between 1100 and 1150us.
    push the envelope, watch it bend

  6. #6
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    Quote Originally Posted by wooden View Post
    The minimum armed throttle is dependent on your ESCs. They're supposed to work with PWM signals between 1000 and 2000us, but in reality, most work with a smaller range of values. Some of my smaller ESCs don't spin the motors until closer to 1250us, while the rest of them typically turn motors on between 1100 and 1150us.
    Are the units in the Motor Commands screen (the scale goes from 1000 to 2000) RPM or us, or does that amount to the same thing? Would the numbers you're using above correspond to the numbers on the Motor Commands screen? If so, then I'm ok, because it's just under 1200 where I can first get a motor to start spinning. I guess I just assumed that, like a car, it would idle in the hundreds : )

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    Senior Pilot wooden's Avatar
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    1000-2000us = microseconds, the frequency of the pulse-width-modulated (PWM) signal being sent to the ESCs.
    push the envelope, watch it bend

  8. #8
    Moderator AeroQuad Core Software Developer kha's Avatar
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    1000-2000us is the pulse length that controls the esc. This pulse is sent between 50 (old analog servos only like this) upto 400 (most ESCs accept this) times per second. AQ sents at 300 or 400 times per sec. for motors and 50 to camera servos.
    quad(X)1: AQ + mega + v2 shield (with baro) + turnigy plush 30A + Turnigy 2217 + APC 12x3.8 (camera onboard)
    quad(X)2: AQ32 at Baloo / DJI F450 / A2212-12 / 30A ESC:s / 10x4.5 (camera onboard)
    quad(X)3: Naze32 / DJI F330 / RCTimer 2212-9 / Aeolian 20A / 8x4.5
    Generic: Turnigy 9x with telemetry mods with FrSky 2Way, GoPro Hero HD, 1.3 & 5.8 vTx

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    Ha! Now I know what the PWM values are in the AQ code. Time to apply this to my simulator's newly coded brushless motor control (with linear rpm vs torque curves).

    BTW, which file is this stuff calculated and output? Does it use the hardware timers to create the PWM pulses?

    Dave.
    Last edited by jabbado; 09-20-2012 at 08:13 AM.

  10. #10
    Moderator AeroQuad Core Software Developer kha's Avatar
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    The output values are calculated in the flightcontrolxxx.h files and outout is done by motorspwmtimer.h (obviously timers are used).
    quad(X)1: AQ + mega + v2 shield (with baro) + turnigy plush 30A + Turnigy 2217 + APC 12x3.8 (camera onboard)
    quad(X)2: AQ32 at Baloo / DJI F450 / A2212-12 / 30A ESC:s / 10x4.5 (camera onboard)
    quad(X)3: Naze32 / DJI F330 / RCTimer 2212-9 / Aeolian 20A / 8x4.5
    Generic: Turnigy 9x with telemetry mods with FrSky 2Way, GoPro Hero HD, 1.3 & 5.8 vTx


 
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