Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers

dc42

@joergs5 said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

If the TMC chip does not report temperatures correctly, isn't it better to measure the temperatures with a sensor yourself (e.g. at the heat sink of the controller which is under max load, so X or Y controller) and take this temperature to decide how to handle fan speed?

If the drivers get hot, they will heat the CPU through the PCB. So you could use a combination of the CPU temperature and the driver warning to handle fan speed.

SnowCrash

@phaedrux said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

@snowcrash to get the renaming to work you would need to use the DWC version 1.22.1 v2 and the special firmware version 2.01 (b1.5?) from here https://forum.duet3d.com/topic/5485/duet-web-control-wishlist-notes-and-priorities/25

But at this point it might just be worth waiting for the next official release of 2.01 and associated DWC version.

Yeah, I think you're absolutely right. It's just a convenience anyway, so I'll wait with this.

@joergs5 said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

If the TMC chip does not report temperatures correctly, isn't it better to measure the temperatures with a sensor yourself (e.g. at the heat sink of the controller which is under max load, so X or Y controller) and take this temperature to decide how to handle fan speed?

Excellent suggestion, @JoergS5, thanks.

Whenever possible I prefer to use the internal circuitry, but in this case external sensor/s do seem like the best solution. The downside would be the need to devise suitable hardware to interface with the Duet (either ready-made or custom) and the additional wiring & clutter.

I'll look into this more closely when I get some free time

@dc42 said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

@joergs5 said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

If the TMC chip does not report temperatures correctly, isn't it better to measure the temperatures with a sensor yourself (e.g. at the heat sink of the controller which is under max load, so X or Y controller) and take this temperature to decide how to handle fan speed?

If the drivers get hot, they will heat the CPU through the PCB. So you could use a combination of the CPU temperature and the driver warning to handle fan speed.

Thanks, @dc42! Sounds great. Could you please give an example of how to accomplish this?

deckingman

@dc42 said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

@joergs5 said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

If the TMC chip does not report temperatures correctly, isn't it better to measure the temperatures with a sensor yourself (e.g. at the heat sink of the controller which is under max load, so X or Y controller) and take this temperature to decide how to handle fan speed?

If the drivers get hot, they will heat the CPU through the PCB. So you could use a combination of the CPU temperature and the driver warning to handle fan speed.

For info, using a thermistor stuck to a driver chip controlling a fan to blow air onto the back of the boards, after an hour or more of printing, I typically see the driver temperature reporting about 15 degrees higher than the CPU temperature. More specifically, with the fan running in thermostatic mode between 40 and 50 deg C, I might see 47 degrees on the driver but only 32 being reported for the CPU. I did calibrate the cpu temperature by using M912 so they both read the same at an ambient of about 22 deg C.

SnowCrash

@deckingman said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

@dc42 said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

@joergs5 said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

If the TMC chip does not report temperatures correctly, isn't it better to measure the temperatures with a sensor yourself (e.g. at the heat sink of the controller which is under max load, so X or Y controller) and take this temperature to decide how to handle fan speed?

If the drivers get hot, they will heat the CPU through the PCB. So you could use a combination of the CPU temperature and the driver warning to handle fan speed.

For info, using a thermistor stuck to a driver chip controlling a fan to blow air onto the back of the boards, after an hour or more of printing, I typically see the driver temperature reporting about 15 degrees higher than the CPU temperature. More specifically, with the fan running in thermostatic mode between 40 and 50 deg C, I might see 47 degrees on the driver but only 32 being reported for the CPU. I did calibrate the cpu temperature by using M912 so they both read the same at an ambient of about 22 deg C.

Awesome, @deckingman, thanks!

In that case, I might switch to monitoring the cpu temp instead of the drivers as it would give me the gradual fan speed ramp up I'm looking for.

How do you monitor that particular temp? (virtual heater number?)

And could you please tell me how you calibrated the cpu temp?

Phaedrux

https://duet3d.dozuki.com/Wiki/Calibrating_the_CPU_temperature

M106 P2 F100 L0.2 B0.5 T35:40 H100:101:102	; Set fan 2 Duet case fan. Turns on when the MCU temperature (virtual heater 100)
; reaches 45C and reaches full speed when the MCU temperature reaches 65C or if any TMC2660 
; drivers (virtual heaters 101 and 102) report that they are over-temperature

This is what I use to control the dual case fans for my enclosure. Works quite well. You can modify the set point to keep the cpu relatively cool and be confident the drivers are fairly close.

deckingman

@snowcrash said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

@deckingman said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

@dc42 said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

@joergs5 said in Help Configuring PWM Fan in Thermostatic Mode for Duet Drivers:

If the TMC chip does not report temperatures correctly, isn't it better to measure the temperatures with a sensor yourself (e.g. at the heat sink of the controller which is under max load, so X or Y controller) and take this temperature to decide how to handle fan speed?

If the drivers get hot, they will heat the CPU through the PCB. So you could use a combination of the CPU temperature and the driver warning to handle fan speed.

For info, using a thermistor stuck to a driver chip controlling a fan to blow air onto the back of the boards, after an hour or more of printing, I typically see the driver temperature reporting about 15 degrees higher than the CPU temperature. More specifically, with the fan running in thermostatic mode between 40 and 50 deg C, I might see 47 degrees on the driver but only 32 being reported for the CPU. I did calibrate the cpu temperature by using M912 so they both read the same at an ambient of about 22 deg C.

Awesome, @deckingman, thanks!

In that case, I might switch to monitoring the cpu temp instead of the drivers as it would give me the gradual fan speed ramp up I'm looking for.

How do you monitor that particular temp? (virtual heater number?)

And could you please tell me how you calibrated the cpu temp?

What I do is stick a thermistor onto whatever it is want to monitor with a dab of epoxy adhesive - in this case a driver chip. I did a bit of a write up on my blog but it's a little out of date with current firmware. https://somei3deas.wordpress.com/2017/04/18/stepper-motor-and-electronics-cooling/

The relevant lines from my current config.g are:

M305 P103 X2 S"Duet\Duex" T100000 B4725 R4700; Set thermistor + ADC parameters for "heater" 2 - this is used to measure stepper chip temperature on Duet

and

M106 P2 S255 I0 F100 H103 T40:50 L125; Set fan 2 value (Duet and Duex fans), PWM signal inversion and frequency. Thermostatic control is turned on

The fan is set to start when then chip temperature is 40 deg C rising to fully on at 50 deg C. However, at very low speeds, the buzzing sound was bit distracting so I added the "L" parameter to inhibit really slow fan speeds. Essentially it comes on at half speed at 40 deg c and ramps up to full speed between 45 and 50. That and PWM frequency are just some things that you have to play around with to suit your particular fan(s).

The calibration of cpu temperature is just applying an offset. The quick and easy way is to you leave the printer say overnight, after which time all temperatures should be more or less at ambient. Turn the printer on and very quickly note the bed temperature, the hot end temperature and the cpu temperature - do it quickly before the cpu starts to warm up. The bed and hot end should be more or less the same - if not, one or other thermistors isn't calibrated correctly. Compare these temperatures with the cpu temperature. Then simply add a positive or negative offset to M912 P0. In may case, the cpu was reading 9.1 degrees high I use M912 P0 S-9.1. (not the minus sign). Now when I first turn the printer on, all temperatures read the same ambient value (within a degree or so).

HTH

SnowCrash

Thank you very much, @Phaedrux & @deckingman!

Definitely something I'd like to try out, but it's a lot to chew on (at least at a glance), so I'll add it to my TODO list and report back once I've had a chance to study it carefully and test it out