Would be nice to set FAN target speed by RPM instead of PWM
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@theruttmeister PID uses feedback. I am describing one way conversion. RPM->(learned curve)->PWM
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@BoA
You already have a sensor measuring RPM to create the control curve... you are going to use that to monitor the fan anyway, the PID loop is such low overhead on something like the Duet that why on earth wouldn't you use it? You would need to create some control logic anyway, doing what dc42 suggests makes a lot of sense as it only needs a new sensor type and can re-use the heater logic.I will also point out that you are also making a flawed assumption:
Fans are designed to push a certain CFM, with a fixed RPM and input voltage.
Taking 2 different CFM fans (that have different RPM ratings), and trying to run them at the same RPM is unlikely to produce the same CFM output. The fan blades are designed for the operating RPM rating and as such will perform differently at a different speed, that relationship between CFM and RPM is not linear.
To truly match CFM output would require a mechanism for measuring that output...Its much easier to just buy fans with matching CFM/static pressure ratings.
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@theruttmeister OK. Perhaps You are right. I build a mass flow sensor once, but for 3d printing it might be an overkill. Just looking on how the blowers are made I thought the major difference is RPMs capability.
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@BoA In my opinion they is only one, good 5015 fan - Sunon MF50151VX-A99
I put it in all my printers and recommend to every one.
Even that it is 12V only it is worth the hassle to add a step-down to run it.
It maybe not the quietest at 100% but is super powerful and if you need to be more quite just run it slower. -
@dragonn said in Would be nice to set FAN target speed by RPM instead of PWM:
Sunon MF50151VX-A99
what about he MF50152VX-1L01C-Q99?
24V and pwm.
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@BoA said in Would be nice to set FAN target speed by RPM instead of PWM:
@theruttmeister OK. Perhaps You are right. I build a mass flow sensor once, but for 3d printing it might be an overkill. Just looking on how the blowers are made I thought the major difference is RPMs capability.
The original request, setting fan speed in rpm not pwm %, is still a good one!
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@Veti said in Would be nice to set FAN target speed by RPM instead of PWM:
@dragonn said in Would be nice to set FAN target speed by RPM instead of PWM:
Sunon MF50151VX-A99
what about he MF50152VX-1L01C-Q99?
24V and pwm.
No idea, first time I see that model. But it isn't available outside in regular shops, only on aliexpress. I am buying A99 in a regular electronics store and paying less for that one.
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@Veti Can I connect MF50152VX-1L01C-Q99 directly to 4pin fan header on duet3? With 24V voltage?
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@BoA
the duet 3 has 4 pin fan connectors for pwm fans.
check that the fan voltage is set to vin. -
@Veti That is clear. My concern was voltage on tacho pin and pwm pin. Well... perhaps only tacho.
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@BoA
i think the hardware overview makes it pretty clearhttps://duet3d.dozuki.com/Wiki/Duet_3_Mainboard_6HC_Hardware_Overview
6 PWM controllable fan channels. 3 of these support 4 wire fans including tacho reading. These can be run from either the input voltage, from 12V, or from external power for added flexibility. Also one always-on fan connector supplied with VIN voltage.
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@Veti Ok. I will give it a try soon
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@BoA said in Would be nice to set FAN target speed by RPM instead of PWM:
My concern was voltage on tacho pin and pwm pin.
they're generally active low to avoid voltage issues
