Connecting 5v pwm fans to duet mini 5+

johnmaundrell

Can anyone advise me how to connect 5v pwm 3 wire fans to a duet mini please.

oliof

@johnmaundrell assuming the third wire is for the tachometer, https://docs.duet3d.com/en/User_manual/Connecting_hardware/Fans_connecting should have you covered

johnmaundrell

@oliof Thanks for your help. The guide says "You can supply a different voltage to the centre pin of the 3-pin jumper, pin VOUTLCx, to run fans at different voltages". This is the bit I am having difficulty with. How do I do this.

droftarts

@johnmaundrell First, check what current (ie amps) your fans use. For example this Noctua 4x20 fan is rated at 0.1A (or 100mA) https://noctua.at/en/products/fan/nf-a4x20-5v/specification. The 5V voltage regulator on the Mini 5+ can supply up to 1A, but this is shared between other components (see https://docs.duet3d.com/Duet3D_hardware/Duet_3_family/Duet_3_Mini_5+_Hardware_Overview#operating-limits). So you should be able to power a couple of these 5V fans from the Duet itself. However, other 5V fans may draw a lot more current, so may need an external buck converter/voltage regulator.

Worth noting is that fans and heaters are switched on the negative side, to GND. So we can supply a constant voltage on the positive side of the fan, and it is switched on and off by the pin the fan is connected to on the negative side.

On the Mini 5+, fan voltage is supplied by the board to the two pairs of fan outputs separately. For OUT3 and OUT4, there is a 3-pin jumper called "LOW CURRENT OUTPUT VOLTAGE SELECT - OUT3-4", and another for OUT5 and OUT6, similarly named (labelled top right on image below). With a jumper, you can choose what voltage to supply, and offers the option of the input voltage (V_FUSED) or 12V. You can also remove the jumper, and supply whatever voltage (between 0-24V) directly to the middle pin, which will power the two fans on that bank with that voltage.

You can supply 5V by using a separate 5V voltage regulator. If your fans don't use much current, you could put a jumper wire from the "5V_EXT" pin on the "5V_PWM" header, just below OUT6 on the wiring diagram, to the middle pin of the "LOW CURRENT OUTPUT VOLTAGE SELECT" of your chosen fan outputs.

You can also wire the positive side of the fan to a 5V pin, eg on one of the IO headers. Connect the negative side of the fan to the out#- (eg out3-) pin of the fan header.

Ian

johnmaundrell

@droftarts Thanks Ian I think I've got it. I will remove the jumper and connect the centre pin of 5v PWM to centre pin of low current output voltage select for out 3 and 4. Regards John

droftarts

@johnmaundrell Did you see the bit about checking the current of your fans? What fans are you using?

Ian

johnmaundrell

@droftarts two at 0.1amp. The fans have 3 wires pos neg and signal I assume I use gnd voutc1 and the bottom pin.

droftarts

@johnmaundrell said in Connecting 5v pwm fans to duet mini 5+:

The fans have 3 wires pos neg and signal I assume I use gnd voutc1 and the bottom pin.

Is the signal wire not a tacho wire? 3-wire fans are usually positive, negative and tacho. If so, it should be wire positive to VOUTLC1+, wire negative to out[#]- (the bottom pin), signal wire is probably the tacho wire, so can got to out[#].tach. Though 3-wire fans usually only report tacho signal correctly at 100%.

Ian

johnmaundrell

@droftarts one is a
Noctua the other is a blurolls. I will set them up as you have advised this evening. The next step is to programme them that will no doubt challenge me a bit more. . Many thanks for your help. Regards John.

johnmaundrell

Ian
I have wired up as discussed but the fans don't run when tested. I think my logic must be wrong.