D3 6HC-12V 4PIN fans and 12V 4PIN pump (brushless) on OUT X ?

pro3d

Duet 3 6HC 1.01 - 12V 4PIN 150ma 2xfans and 12V 4PIN pump (800ma brushless) on OUT X (4-6)?

I know there are other options, but I want to know if its OK to add a buck converter to OUT X (4-6) V_OUT/GND to run my 12V fans and my 12V pump from that?

The pump and the fans both have tacho and PWM so if the above is OK then what about the PWM signal? Is this still 24V? and do I need to add resistors for this to be right?

The firmware would be something like this:
M950 F5 C"!out5+out5.tach"
M106 P5 C"Water pump" S1 H1 T50

M950 F6 C"!out6+out6.tach"
M106 P6 C"Radiator Fan" S1 H1 T50

Since being a brushless pump would this be ok? What about the PWM signal? Can it be used without any mods?

Or must it be something like this:

droftarts

@pro3d The OUT pin of the fan connectors switches to GND, it doesn't supply a positive 0 to 5V signal. The 150mA fans should be okay running on the Duet 12V regulator which has a 800ma limit (total for out3-8 ports, when 12V selected). Alternatively supply 12V from a buck converter.

The pump would need a separate 12V supply due to the current it draws, but assuming it's only two wire, you can connect the negative side to one of the fan OUT pins, and control it via PWM, as the fan OUT pins are protected by flyback diodes. See https://docs.duet3d.com/en/User_manual/Connecting_hardware/Motors_servos#connecting-dc-motors

Ian

pro3d

@droftarts

I might have been unclear in op. As I wrote in I know there are other options, but I am asking this:

Can I use a buck 24V-12V on OUT 6 V_OUTLC1/GND and connect my 12V fans to the buck+out6.tach+out6(pwm). Will the PWM signal be 24V now? Does the PWM need to be lowered as well?

I want to control the pump separate from the fans, so I was wondering if I could connect the pump to the same buck for 12V power and then use out5.tach+out5(pwm)

The total current draw will be 1.1A so this is only possible using OUT 4-6 on 24V

If the above is possible I wonder what to do with the PWM signal, does it still send 24V? and does it need resistors to work properly on 12V fan/pump

I just want answer to the above and not other options. I am exploring if this is possible^ and if not, I will connect the pump to OUT 0 on 12V there, then run tacho to another free pin somewhere

moth4017

@droftarts What is the maximum current that each FET can handle using an external power supply?

droftarts

@pro3d said in D3 6HC-12V 4PIN fans and 12V 4PIN pump (brushless) on OUT X ?:

Can I use a buck 24V-12V on OUT 6 V_OUTLC1/GND and connect my 12V fans to the buck+out6.tach+out6(pwm).

Yes, assuming that your are supplying 24V VIN, and the fan voltage selector is set correctly. The pins, jumpers and connectors are rated at 3A. Though you could just wire the buck converter back to the PSU.

Will the PWM signal be 24V now? Does the PWM need to be lowered as well?

No. On the fan connectors, the PWM-capable out# pin switches to ground; it does not supply a voltage. Voltage is supplied constantly to the fan/motor positive side from a 12V or 24V pin, and is turned on and off on the negative side by the out# pin. This 'negative' PWM signal is what normal 4-wire fans expect, and they should have an internal pull up resistor to stop the signal 'floating' when turned off.

There are positive voltage PWM pins on the board (5V PWM header for laser/servos/vfd control), but isn't required for fans, dc motors and heaters.

I want to control the pump separate from the fans, so I was wondering if I could connect the pump to the same buck for 12V power and then use out5.tach+out5(pwm)

Yes, assuming your buck converter can take the combined current requirement of fans and pump.

Ian

droftarts

@moth4017 said in D3 6HC-12V 4PIN fans and 12V 4PIN pump (brushless) on OUT X ?:

@droftarts What is the maximum current that each FET can handle using an external power supply?

According to the ibom on Github https://github.com/Duet3D/Duet3-Mainboard-6HC/tree/master/Duet3_Mainboard_6HC_v1.01 it's a DMT6018LDR. If I'm reading the datasheet correctly https://www.diodes.com/assets/Datasheets/DMT6018LDR.pdf, it has a maximum rating of 8.8A.

Ian

dc42

@pro3d you should never connect a buck converter to the switched pin of an OUT port.

The current draw of the two fans is low enough for you to drive them directly from two 4-pin OUT ports with the voltage selection jumper for those outputs set to the 12V position.

The motor draws too much current from 12V so it can't be connected in this way. You can connect the input of your buck converter to the 24V VIN and connect the 12V output to the positive motor wire. If the motor PWM control allows you to turn the motor off then you can connect the other 3 wires to the corresponding pins of another 4-pin fan connector. IOW connect the motor just as you would connect a fan except that instead of connecting the positive motor wire to the VOUTLC pin of the 4-pin connector, connect it to +12V from your buck regulator.

cosmowave

@pro3d
Another possibility could be to power the pump with the bedheater out, if it is free.
I power my waterpump with the bedheater to be able to completely shut off the pump with a "M42" command. With PWM=0, the pump will not fully turn off...
But i run a 12V system. Not sure if you can wire the buck converter to the bedheater.... i think it should be possible...