Control 5V fan speed on 5v_pwm port

[ctilley79]

Questions about 5V out on a Duet 3 Mini 5

Ok. I'm trying to pwm control this case fan. I can't seem to find the pin name, and I want to make sure I understand this correctly. It seems pwm for this port is shared with out_6. Does that mean if I have another fan on out_6, the pwm will apply the same value to both the 5v pwm port and fan I have hooked up to the regular out_6? I'm also not sure what buffered means. Can anyone shed some light? Would I be better off using an IO port for the fan?

[jay_s_uk]

@ctilley79 yes, that pin is shared with out6 so whatevers going on on out6 will go on here too.
It's buffered because the MCU is 3.3v and the buffered outputs are "buffered" to output 5v

[ctilley79]

@jay_s_uk Ok. so this isn't an option for me then. Can I use an I/O port to power a fan? Is there enough power there?

[jay_s_uk]

@ctilley79 no, you can't control a fan from an IO. You could use a spare heater output if you have one

[ctilley79]

@jay_s_uk A spare heater runs at Vin though. I'll probably move my part fan to out_3. That should do the trick.

[deckingman]

@ctilley79 PWM switches the negative side, not the positive. So you could probably still use a heater port as @jay_s_uk suggested. This is untested but if you connect the positive side of the fan to a 5v source somewhere, then connect the negative side to the negative of a heater connection, it should work.

[jay_s_uk]

@deckingman yes, that will work

[dc42]

@ctilley79 is the 5V fan a 2-wire or a 4-wire fan? It should be possible to run a 5V 4-wire fan from that 5V PWM port, but not a 2-wire fan.

[ctilley79]

@dc42 said in Control 5V fan speed on 5v_pwm port:

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It's a 2 wire fan, so that probably explains the issue.

[ctilley79]

@deckingman That did the trick. Thank you