Roto toolboard extra fans

[Jords27]

Hello everyone,

I was wondering if it would be possible to add an extra fan to the Roto Toolboard? I have already used up OUT_1 and OUT_2, but I’m considering adding an extra driver circuit on IO_0_OUT to connect another fan. Would this be feasible or is there another option?

Additionally, I’m exploring the use of only 4-wire fans. Would it be possible to connect the tachometer and PWM signals from such a fan to OUT2 on the Roto Toolboard, while powering the fan from an external source?

Thank you all in advance for your help!

[droftarts]

@Jords27 Yes, I think you could drive a MOSFET/relay from IO_0_OUT to control a fan. Note that IO_0_OUT is the only I/O output (as distinct from OUT outputs) that offers PWM control: https://docs.duet3d.com/Duet3D_hardware/Duet_3_family/Duet_3_Roto_Toolboard#inputoutput.

Yes, you can use the OUT2 tacho input for any fan input, it just needs to be declared in the corresponding M950 command.

However, the OUT2 PWM signal is PWM-to-GND, and looking at the Roto schematic (see https://github.com/Duet3D/Duet3-RotoToolboard/blob/master/v1.0/Duet3_TB_Roto_Schematic_v1.0.pdf), I think out2 cannot be used to sink voltages of more than 5V. As most fans take the input voltage, and use that as the voltage for the PWM signal, it will need to be a 5V fan, not 12V or 24V.

See the description and notes for OUT0, OUT1 and OUT2 here https://docs.duet3d.com/Duet3D_hardware/Duet_3_family/Duet_3_Roto_Toolboard#description-of-connections

Ian

[dc42]

@droftarts @Jords27 OUT2 can safely sink more than 5V, it's just that the OUT2 connector is provided with 5V to match the Roto hot end fan. However, if you use a 4-wire fan then you would connect OUT2_NEG to the PWM control input of that fan and it won't see more than about 5V anyway. You will need to invert the OUT2 pin in your M950 command.

[Jords27]

@dc42 @droftarts thank you again! I'll get back to experimenting and will post an update on my progress.