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One Heater, two Temps 0.6

Posted by rmark1 
One Heater, two Temps 0.6
September 15, 2024 07:19AM
Hi,
Bit of an odd one here - please bear with me.

I have a spare Duet 0.6 and a spare heated bed (well, two in fact!). I am building a heated filament box and want to use the Duet 0.6 to control it. The heated bed will be my heat source. I will need to control the heated bed with two thermistors, one for the bed itself, to keep the temperature at a reasonable level, and one to control the box/chamber temperature.

Is there a way to use two thermistors to control one heated bed in firmware 1.26? I do have an alternative way but it is a bit of a kludge so I would prefer to use the Duet 0.6 for both tasks.

Many thanks for your help in advance.

Richard Marklew.
Re: One Heater, two Temps 0.6
September 16, 2024 03:07AM
You might be able to use the M143 command to use the second thermistor to turn the heater off if it gets too hot. See [docs.duet3d.com]. In RRF1 you would need to configure the second thermistor as a "virtual heater".

Alternatively, you could power the heater at a lower voltage than it is rated for so that it can't get too hot.



Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: One Heater, two Temps 0.6
September 16, 2024 04:22AM
Hi DC42,
Thanks for your reply. Using M143 sounds like a good solution. I have also thought about using an SSR to make a logical AND gate. One other approach is to use a DHT (such as DHT22) and sense the box/chamber temperature through that. What do you think?

Cheers,
Richard.
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