Setting number of samples for pwm averaging

[badoobadoop]

Hello all,

I would like to know how many data points or what length of time the PWM output for a heater is being averaged over and how we can change that. I did see in another post that 20 seconds was mentioned as the running average period, but then I saw a few seconds being mentioned. It would be nice to have a more instantaneous PWM output that can be recorded.

For reference, I am talking about the "heat.heaters[].avgPWM" command.

I am using a Duet 2 Wifi running RRF 3.4.2rc1

Thanks in advance!

[dc42]

@badoobadoop the code is in file src/Heating/LocalHeater.cpp around line 480:

	constexpr float avgFactor = HeatSampleIntervalMillis/(HeatPwmAverageTime * SecondsToMillis);
	averagePWM = (averagePWM * (1.0 - avgFactor)) + (lastPwm * avgFactor);

The two constants are defined in CANlib/src/RRF3Common.h like this:

constexpr uint32_t HeatSampleIntervalMillis = 250;		// interval between taking temperature samples
constexpr float HeatPwmAverageTime = 5.0;			// Seconds

The intention is that the value reported for averagePWM is the instantaneous PWM value fed through a low pass filter with a time constant of 5 seconds.

[badoobadoop]

@dc42 Thank you! That definitely makes sense. I appreciate the help!