24 Volts Bed Heater Problem
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@drmaestro, most switching power supply are good at sensing output power and shut down so in your case you doubly got lucky (go out and buy a lotto ticket)
What I would do is to disconnect the heat pad and the 12V fan and see what works and doesn't work.
24V is good but you'd need a larger supply and run the heat pad via a relay as the Duet is not capable of powering it directly. -
Actually a 24V supply is better for trying to use a higher wattage heater, less current required for the same power.
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@drmaestro, 500 watts for a 200x200 mm is pretty high. Is the bed only 200x200 or are you improvising with a smaller pad?
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@drmaestro said in 24 Volts Bed Heater Problem:
@joel I should probably have gone with this https://www.aliexpress.com/item/32327554677.html?spm=2114.12010612.8148356.10.3dd87d80abwHH4 insteatd of this https://www.aliexpress.com/item/2050749273.html?spm=2114.12010612.8148356.12.3dd87d80abwHH4
yes, 200W is more appropriate for that bed size anyway.
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I would say that 200W is good if your build plate is 200x200. If your build plate is 300x300, I would stick with the 500W heat pad and increase the size of the power supply and run the heater via a relay. (switch to bang/bang operation for a relay)
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@joel said in 24 Volts Bed Heater Problem:
@drmaestro said in 24 Volts Bed Heater Problem:
@joel I should probably have gone with this https://www.aliexpress.com/item/32327554677.html?spm=2114.12010612.8148356.10.3dd87d80abwHH4 insteatd of this https://www.aliexpress.com/item/2050749273.html?spm=2114.12010612.8148356.12.3dd87d80abwHH4
yes, 200W is more appropriate for that bed size anyway.
What size ( wattage ) nozzle heater are you using?
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If you got the 200W bed heater and if your nozzle heater is the standard 40 Watt, say that leaves you with 60W for everything else ( you probably don't want to run right to 350Watts of the supply. 60W is 2.5 Amps at 24V, you still might be cutting it close with the duet, steppers, and fans, but you could push that margin if you want. I would also step up to a 480W supply.
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@joel I have a 50 watts hot-end heater
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@joel I haven't been able to find one, I'll search for it.
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@jens55 I have a 220x220 bed.
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OK, 10W more than my guess. I think you would be better off with a bigger power supply, you could try the one you have and if it runs, run it till it quits.
With a 200W bed heater, the duet will be fine without a relay.
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I don't know where you are, but I saw some 480 Watt on Amazon.
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@joel I have tried to run the hotend fan and also the cooling fan (the 24 volts one) using the always on fan connectors and they aren't working. Maybe there is a problem with the fans themselves or the wiring (I use a 12 volts always on fan for cooling the Duet board and it is working without a problem on the always on connectors).
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For fans, I think you can power 5V fans from the duet, other than that, the fans have to match your supply voltage, so you will need 24V fans. You also have to set the fan voltage source on the duet
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For the hot end fan, I don't think it comes on until a certain temperature is reached, I think set in the config file. For cooling fan, are you talking about the part cooler?
Are you starting with the same config file from the previous setup?
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Are you aware that most fans are polarity sensitive? They can also be destroyed by wrong polarity so it's possible that you killed them.
I would suggest that you stop using the 12V fan until you got all your other issues sorted out and then read up on how to connect it to a 24V source - it is not as straight forward as you think. -
@joel Yes, normally it starts at around 45-50 degrees but I tried to heat it to 80 degrees and it didn't start.
Cooling fan = part cooler
I am using almost the same config, except I added the second 12 volts fan as a cooling fan to tool one (orisignally both of my fans where connected to a single fan output, now that one of them is 12 volts, I had to use a second fan output).
Either way, none of the fans (part cooling and hotend) are working, even if they are on always on connector, so there definitely is a problem on the fans or the wiring....
@jens55 I am aware of the polarity issue and was careful to wire the right polarity.
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@drmaestro said in 24 Volts Bed Heater Problem:
@jens55 Is there a possibility that I might have blown a fuse while trying to use the bed?
Yes, if the bed heater doesn't work at all now but the rest of the Duet does. The bed heater fuse on the Duet is rated at 15A. It would likely carry 20A for several minutes before failing. You can substitute a 20A fuse at your own risk.
Duet WiFi hardware designer and firmware engineer
Please do not ask me for Duet support via PM or email, use the forum
http://www.escher3d.com, https://miscsolutions.wordpress.com -
The bed heater works but immediately resets the duet, as the power supply cannot keep up with the 500 Watts request (it is a 350 Watts PSU). I ordered a 200 Watts bed heater now. I assume the circuit itself is ok, as if it was burn't I wouldn't be seeing any increase in the temperature.
As a side note, I removed the fan connectors, removed the crimps, connected them directly to the PSU to individually test them and they work, so it is probably some bad wiring by me creating the 24 volts fans not working problem.
I read the fan page on the wiki. As I understand, it is possible to either use all 5 volts fans (I don't have any), use all 24 volts fans (in that case I need 1 more 24 volts blower and a 24 volts large fan to cool the Duet board), use all 12 volts fans (in that case I'll need a buck converter, that I already have, and connect the +and - inputs of the converter to my 24 Volts PSU, and connect the positive output to V-fan jumper. I that case, all of the fans (PWM and always on) will be 12 volts. Or in my case, if I want to use 2 24 volts and 2 12 volts fans, I need to apply 24 volts to V-fan jumper (which means I can leave the jumper in place, as my PSU is 24 volts and V in will provide that 24 volts), however for the 12 volt fans I need to apply 12 volts from a buck converter, but the negative ends will go to the Fan - connectors. I assume I can use a single buck converter for supplying 2 12 Volts fans (the buck coverter can output 3 A, so it should be enough). My best option, until I have a all 24 Volts setup, seems to use the last option, which will require a minimal chang in wiring only.
Anything wrong with my understanding?
