Active FAN when heater is ON

Sim234

Hello,

i just installed my Duet2 ethernet (V1.04a) on my 3D printer here and I have faced a little difficulty here. Firmware version is 2.01

I have a chamber heater with fans for spreading the heat around. The fans are on a separated connection.
So right now I plugged my heater in heater E6 connection and my fan on E3 fan connection (on the DUEX 5 board).
My problem is that I can't find a way to start the fan as soon as the heater is turned on. I could use a thermostatic control, but the thermistor is quite far away from the heater and i'm pretty sure I'll burn some stuff before getting a temperature rise to start the fan. Is there a way to start the fan on at full power as soon as I start the heater without having it on all the time?
I don't want to simply have the fan controlled by separate G-code because there is too much risk of someone forgetting to turn it on.

thank you and have a nice day

Phaedrux

If you have a spare thermistor and open connector on the board, you could place it closer to the heater and use it to control the fan.

dc42

I assume you are using an SSR to control the heater. How about connecting the fan and the SSR control terminals in parallel?

Sim234

@phaedrux I could put it straight on the heater, but then I got 2 heaters...
I don't love this solution, but it's a good backup.

thank you for your help

Sim234

@dc42
Yes I can do this. I was more looking for a straight ON FAN when heating, but this seems safe enough.
When I hooked it up to another output, I had problems with PWM.
I'll test it and see what it does.

thank you!

Sim234

Hi guys,

I did some testing this morning.
in fact, what I see as a problem here is the remaining heat on the heater. It can be very hot when I stop heating with it.
I need the fan to continue running for a few seconds once the heater is off to cool it down.
I was so sure to have this kind of feature in the firmware, that i didn't check at all. This is the behavior I see as optimal:

-> heater ON -> Turn fan ON
-> Heater OFF -> Let fan ON for a delay then turn OFF

It seems simple, but I can't seem to find a way to implement this. If anybody knows how to do this, then I would love to hear it. I see the solution with the thermistor can do this, but I thought it might be simpler to have it straight from the firmware.

thank you and have a nice day

barcwik

Hi guys!

I'm also looking for solution for this problem. Can anyone help us?

A Former User

@barcwik
If you're happy with controlling it through c-code without feedback then: (however I'd rather put the fan under thermostatic control. Maybe explicitly starting it and switching to thermostatic control once chamber temperature has been reached.)

-> heater ON -> Turn fan ON

M106 P2 S255 ;turn on chamber/fan2
M141 S50 ;turn on chamber heater
M149 ;optional wait for chamber temperature

-> Heater OFF -> Let fan ON for a delay then turn OFF

M141 S0 ;turn off chamber heater
G4 S10 ;wait 10 seconds
M106 P2 S0 ;turn off chamber/fan2

you'd also want to consider what happens when things don't go according to plan, and where to place the g-code

Huh, didn't intend to tag Sim234, but seems it does so if you qoute and delete the refrence in the post.