Parallel 2x smaller heater outputs?
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Just bought a 3 Mini 5+ wifi and I would like to parallel the smaller heater outputs. Can anyone confirm this works before I damage the board by trying it? Worst case I could diode the outputs I suppose but I don't want to if I don't have to.
This is to power a enclosure heater 24V at 200W.
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to power a enclosure heater 24V at 200W, I would like to parallel the smaller heater outputs.
For this to work, you’d have to couple the Gate pins of the MOSFETs, too. Instead, you better use a DC/DC SSR (Solid State Relais) which can be controlled by one of the heater outputs. Please note that the heater outputs control the GND signal, not V+.
May I ask how large your heated enclosure will be? With a size to fit a typical 3D printer, 200W won’t help too much.
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@infiniteloop said in Parallel 2x smaller heater outputs?:
to power a enclosure heater 24V at 200W, I would like to parallel the smaller heater outputs.
For this to work, you’d have to couple the Gate pins of the MOSFETs, too. Instead, you better use a DC/DC SSR (Solid State Relais) which can be controlled by one of the heater outputs. Please note that the heater outputs control the GND signal, not V+.
May I ask how large your heated enclosure will be? With a size to fit a typical 3D printer, 200W won’t help too much.
Can't I configure them with the same settings and temp probe and they will trigger at the same time? Yeah I already have a ssr but I'm trying to get rid of it if I can to get a more compact setup.
It's just bigger than my 10x10x10 area. I mean it's just speeding up heating up the air that the bed already does.
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Can't I configure them with the same settings and temp probe and they will trigger at the same time?
No, I don't think there is any GCode available to couple two outputs as tightly as required in software.
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@SINTORMAN you can get two outputs together as one in M950
(RRF 3.4 and later) When using M950 to create a heater, multiple port names can be provided, separated by the '+' sign. The maximum number of ports that may be used depends on the board. Any CAN address at the start of the port name string applies to all the port names. -
you can get two outputs together as one in M950
Won’t the firmware trigger the gates sequentially, I.e. one after the other? Then, the MOSFET who comes first takes the full load - for just a moment, depending on how close the loop is. So I imagine that, if you couple the gates software-only, one of the MOSFETs has to handle the switch-on current alone. At 24V, 200W, that’s beyond its specs. Or is my assumption off the rails?
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@infiniteloop probably, i've never tried it. I think its more for multiple heaters working together rather than the same heater across multiple outputs.
As you say, a relay would be better -
@infiniteloop I'm guessing that would still be in spec as it would be not even milliseconds that it would see full load. Could also put an inductor in series to correct that issue.. hmm.
Again would be pretty sweet to have everything driven from a single board.
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@SINTORMAN 200W at 24V is 8.33A. The extruder heater and stepper motor outputs on the Mini 5+ are fused at 10A (not 7.5A as I earlier wrote, that's on Duet 2), which is uncomfortably close, and you may blow the fuse with the motors running as well. I don’t recommend increasing the fuse, it’s likely to lead to failure of other board components. Use the bed output, or an SSR.
Ian
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@droftarts said in Parallel 2x smaller heater outputs?:
@SINTORMAN 200W at 24V is 8.33A. The extruder heater and stepper motor outputs on the Mini 5+ are fused at 10A (not 7.5A as I earlier wrote, that's on Duet 2), which is uncomfortably close, and you may blow the fuse with the motors running as well. I don’t recommend increasing the fuse, it’s likely to lead to failure of other board components. Use the bed output, or an SSR.
Ian
Ian,
So just to make sure I understand correctly. The bed heater circuit has it's own 15A fuse. Then the 10A fuse not only feeds the two aux heater circuits but also the stepper drivers? Shouldn't that be advertised in pretty big bold print that you can't actually run 2 loads of 5A each while the unit is running (steppers rotating)?
