How do I scale and limit PWM for motor?

Ground Control Software Mission Planner
1

Hi,

I’d like to make sure my motor never gets more than 8 Volts.

I’m running ArduPlane on a Matek F405-Wing FC. I can determine the throttle PWM which gives me 8 Volts at the output of the ESC.

What is the best way to scale and limit THR in Mission Planner so that

  1. I get the full control stick range in manual flight mode (bottom = THR off, top = THR maximum = PPM for 8 V), and

  2. no matter which flight mode (e.g. Return To Launch, Fly by Wire, Manual) the THR PPM never goes above the limit for 8 V?

Many thanks for any help
Jenny

2

servo3_min and servo3_max to the pwm values you want is the easiest way. If your throttle output isn’t on channel 3, use whatever channel number it is on.

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3

Thank you James :slight_smile:

Unfortunately this only limits maximum THR, but it does not scale it. At about 50 % of stick movement from bottom to top, I get maximum THR. Any additional stick movement does not change anything, it stays at the maximum THR value of 1600 PPM.

Instead, I’d like to have:

THR stick at bottom = zero throttle
THR stick at top = maximum throttle at 1600 PPM
Everything in between = linear proportional PPM to stick movement

In other words, I’d like the THR stick to behave like usual, just with a lower PPM range, not from 1100 to 1900, but from 1100 to 1600.

What else can I do so that I get the full stick movement range from bottom to top?

Many thanks
Jenny

4

That’s a transmitter function, not something that the flight controller or ground station software can set.

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5

Ok, thanks!

So on the transmitter I scale stick movement linear from 1100 to 1600, and additionally on the ground station software I limit maximum to 1600 via servoN_max, right?

Am I safe that way, to never get more than 1600 PWM, no matter which flight mode is selected?

6

Yes, but if you want to be super sure and have the equipment to test, I’d suggest also setting the thr_max param (which limits the throttle to a percentage of servoN_max, but only for assisted modes - manual modes is simply pass through) and increment it up from say 60% to 100% in steps, with the plane in fbwa.

1 Like