connecting a fan to heater 3

[da97ed]

Hi
I'm trying to connect a thermostatically controlled fan at the heater 3 pin but I'm not sure how to wire this. The Fan should be Controlled by the MCU temperature.

This is what I set up in my config.g so far:

M308 S3 A"MCU" Y"mcu-temp" ;display MCU temp within the graph
M950 H3 C"exp.heater3" T3 ;creating heater 3																																			
M950 F3 C"fan3" Q500 ;creating fan 3																			
M106 P3 C"MCU" S3 H3 T40:60 ;control Fan 3 thermostatically. start fan at 40 degrees and rise continually PWM Frequency to 255 when the temperature reached 60 degrees.

I would wire the fan as follows: Connect Fan + to heater3 pin and Fan - to GND.
Is this correct regarding wiring and my config GCode?

Thank you all in advance.

[rjenkinsgb]

@da97ed said in connecting a fan to heater 3:

I would wire the fan as follows: Connect Fan + to heater3 pin and Fan - to GND.

Not sure on the config, but the fan negative should be to the heater pin; the Duet boards switch heater outputs to ground/0V and the positive is the permanent side.

[da97ed]

@rjenkinsgb did exactly that and fried my board... thanks for nothing

[Phaedrux]

How exactly did you have it connected?

How is it fried?

What Duet board are you using?

Connecting a fan to a heater port is much the same as connecting a fan to a fan port. + to + and - to -

[rjenkinsgb]

@da97ed said in connecting a fan to heater 3:

did exactly that and fried my board...

That is not possible, just from using the connections I said. You must have something wrong elsewhere.

This is a typical heater output, grabbed from a Duet board schematic - it has a power MOFSET switch to ground ( - out ) and permanent positive from the fuse, exactly as I described.

[da97ed]

@phaedrux I used a duet wifi v1.04.
Connected the 24V - to exp.heater3 on the expansion header and positive to VIN. Despite the wiring of the Fan to heater3 I didn't change anything.
After powering up, all my heaters (E0 and Bed) went crazy and started to heat without any command. I immediately killed the power and disconnected the fan. Since, the DIAG LED ist constantly red, so are the LED next to the USB connector and 3.3+(green) and 5V+.
There are no optical signs of a damage to the board however I am unable to establish a connection to it. I have already tried to erase the FW using the erase Jumper but still I cant connect to it. After 6s the MCU is too hot to touch it.
Im not sure what went wrong, would appreciate any further help. Thanks

[rjenkinsgb]

@da97ed
Ah.. Duet 2 not Duet 3... Seeing 3s everywhere in the question, it appeared to be a Duet 3.

The expansion connector is only low level logic signals and not capable of controlling any heater or fan directly, without a Duex connected to handle the higher voltage and current control needed..

I gave the answer to suit a dedicated heater output port, as did Phaedrux; there was unfortunately no clue in the question that your board did not have one.

(The Duets I've used do have the heater 3 power connector onboard, as per the circuit fragment, so again no clue of anything different).