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Author Topic: question PWM or Blheli or?  (Read 41328 times)

Offline dave siegler

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question PWM or Blheli or?
« on: March 26, 2024, 07:52:48 PM »
So I have a timer design that i have been using, it works great.  It has a MEMS accelerometer so can trim up the power for climbs and turns. 

Mine uses the simple servo pulses from the timer to the ESC. 

Does anyone use the higher speed protocols that the ESC can use directly like Blheli to get faster responses?

The drone guys get higher performance out of the motor cooler operation and quieter operation,  I know its not the same application. 

So does a faster timer to ESC protocol help?     
Dave Siegler
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Offline CircuitFlyer

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Re: question PWM or Blheli or?
« Reply #1 on: March 27, 2024, 09:33:17 AM »
I can't see how it would make a noticeable difference.  Relatively speaking, things just don't happen that fast in control line.  A typical PWM signal updates every .02 seconds.  For a typical stunter that equates to about 16 inches of linear travel and approximately 3 rotations of the prop.  How much change in velocity happens over that 16 inches?  Is it enough to warrant faster updates?  Oneshot125 can update 8 times faster, approximately every 2 inches along the flight path and 1/3 of a rotation of the prop (maybe 5 pulses from the RPM sensor).  What is the loop time on your PID controller?  How accurate is the RPM calculations based on fewer pulses?  A lot of things to consider.

I think you would see a much larger gain in performance just by using ESC's that have very little to no input filtering before going to a faster protocol.
Paul Emmerson
Spinning electrons in circles in Mississauga, Ontario, Canada DIY Control Line Timers - www.circuitflyer.com

Offline dave siegler

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Re: question PWM or Blheli or?
« Reply #2 on: March 27, 2024, 06:50:18 PM »
most likely you are right.  But I wonder if people get access to other times in the esc's data table.  The data that shows up on drone flight controller is impressive
Dave Siegler
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Online Dennis Toth

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Re: question PWM or Blheli or?
« Reply #3 on: April 11, 2024, 06:25:58 AM »
CF,
Are you using 8 as the PWM in the ESC for your .02 sec? The BadAss motors use 8 as the standard starting point. I guess another option in to increase that to 12, but this will increase temps in the ESC and motor some need to make sure the cooling is very good.

Best,    DennisT

Offline CircuitFlyer

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Re: question PWM or Blheli or?
« Reply #4 on: April 11, 2024, 09:06:47 AM »
Dennis,

Dave was referring to the PWM rate of the throttle signal used for the ESC input.  Control line timers currently use 50Hz, 50 times a second or one pulse every .02 seconds. 

I think you are referring to the PWM rate used to chop up the motor voltage signal on the ESC output.  8k, 12k or 16kHz.  Yes, I agree, it can be confusing.
Paul Emmerson
Spinning electrons in circles in Mississauga, Ontario, Canada DIY Control Line Timers - www.circuitflyer.com

Online Dennis Toth

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Re: question PWM or Blheli or?
« Reply #5 on: April 12, 2024, 07:28:25 AM »
CF,
Does the PWM rate set to a higher frequency (say 12 or 16) do anything for quicker response to load (like in a hard conner and vertical climb?

Best,    DennisT

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Re: question PWM or Blheli or?
« Reply #6 on: April 12, 2024, 03:16:41 PM »
Not very likely.  In some cases you might gain a tiny bit more efficiency (at the expense of more heat) and feel like you have gained a little more midrange power but, no, it won't necessarily respond any faster.
Paul Emmerson
Spinning electrons in circles in Mississauga, Ontario, Canada DIY Control Line Timers - www.circuitflyer.com


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