One common cable for ground?
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Hello!
I have 3 fans, a thermistor and a heater on my print head. All in all 10 cables. Since the thermistor cable is now broken, I would like to interrupt the cables at the print head and continue them with a highly flexible cable. On this occasion: can I connect the 5 ground cables all together and lead them to the board as one cable? Do I have to split them all up again or is it enough to put them all on the heater mass?
I have a Duet 2 Wifi.
Thanks!
Markus Müller -
@mmueller70 It is a bad idea to try to use one common ground wire for both the heater and the thermistor connections. The cable will have some finite value of resistance. As current pulses through it for the heater there will be a voltage drop that will look like a signal on the thermistor lead. Fans are also pretty noisy, electrically. Keeping them isolated from the thermistor is also a good idea.
Leads to the thermistor, heater, and fans should all be twisted, pair-wise. That reduces coupling between the leads and EM radiation.
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@mmueller70 The MOSFETS that control heaters and fans switch the negative (ground) side not the positive side, so no you can't connect them together. You could possibly connect all the positive sides of the fans together though.
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@mmueller70 it's as @deckingman says, you can use a common positive wire for all fans that use the same supply voltage. The thermistor cannot share a ground wire with anything else except another thermistor, because Duet boards use separate analog and digital grounds in order to provide better accuracy and less noise in the readings.
