24 Volts Bed Heater Problem
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Hi,
I was upgrading my configuration from 12 volts to 24 volts. I used a 24 Volts 500 Watts silicone heater for the bed. It is directly connected to the Duet. Whenever I try to increase the bed temperature Duet resets immediately. Is it because 500 watts is too much? Also, none of my fans (PWM and thermostatic) work anymore (the continous fan works). Did I burn something or blow a fuse? I am on Duet Wifi 1.04.
Thanks...
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@drmaestro, how big is your 24V power supply?
Chances are you are drawing too much power for this configuration. -
I think the heater outputs are good for 18A. Your 24 Volt 500 Watt heater would draw about 21A which is a little over but....
What are you using for a power supply?
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@joel I have a Mean Well: LRS-350-24, 24VDC 14.6A 350W SMPS
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@drmaestro said in 24 Volts Bed Heater Problem:
12 volts to 24 volts
Did you also change your hotend heater and fans to 24v?
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@drmaestro said in 24 Volts Bed Heater Problem:
@joel I have a Mean Well: LRS-350-24, 24VDC 14.6A 350W SMPS
You power supply is too small. you are trying to heat up a 500W pad with a 350W power supply. It is likely shutting down.
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Can't draw 600W from a 350W power supply ....
... and Phaedrux, good call on the fans and hotend heater(s) -
@phaedrux Partially. I've changed the hotend fan to 24 volts. It is thermostatically controlled, however it isn't working when I increase the temperature. I also have 2 cooling fans however 1 of them is 12 volts, so I am using a voltage regulator for this one.
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@drmaestro said in 24 Volts Bed Heater Problem:
@phaedrux Partially. I've changed the hotend fan to 24 volts. It is thermostatically controlled, however it isn't working when I increase the temperature. I also have 2 cooling fans however 1 of them is 12 volts, so I am using a voltage regulator for this one.
It is highly likely that the 12V fan is not set up correctly.
The question of the hot end heater is still open. -
@jens55 Is there a possibility that I might have blown a fuse while trying to use the bed?
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@joel said in 24 Volts Bed Heater Problem:
@drmaestro said in 24 Volts Bed Heater Problem:
@joel I have a Mean Well: LRS-350-24, 24VDC 14.6A 350W SMPS
You power supply is too small. you are trying to heat up a 500W pad with a 350W power supply. It is likely shutting down.
Another point, your heating pad is also too big for the duet. Your best bet it to drive a relay with the duet and have the relay provide power to the heater pad.
You could get a second 24V supply just for the bed heater ( would recommend something a bit bigger than the 500 Watts you heater needs ) and then use the existing supply ( if not damaged ) for the duet, fans, and nozzle heater.
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@drmaestro, there are so many red flags in this 'upgrade' that it is hard to say what all you did to the board. Yes, fuses are a possibility. So is mosfets ....
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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?
I think there is a fuse inside the Mean well power supply, you will have to open it up to check. I have a couple of Mean wells and they are soldered in.
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@joel I may have to change the heating pad instead, as I don't have enough free space for an additional power supply. What is the highest wattage that Duet can directly operate?
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@joel The Meanwell is working. I can power-up the printer, move the motors and use the hotend heater, so I think Mean Well is ok.
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@drmaestro said in 24 Volts Bed Heater Problem:
@joel The Meanwell is working. I can power-up the printer, move the motors and use the hotend heater, so I think Mean Well is ok.
You lucked out ....
I believe there is a separate fuse for the bed heater which is likely blown. -
@jens55 Interestingly it isn't. If I try to increase the neated bed temperature it starts to rise 1-2 degrees but then resets. So I think it isn't blown (I am not doing it anymore of course).
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@drmaestro said in 24 Volts Bed Heater Problem:
@joel I may have to change the heating pad instead, as I don't have enough free space for an additional power supply. What is the highest wattage that Duet can directly operate?
The switch the duet uses says 18A, you probably want to be something less than that to have some margin. If you say 15A, that would be a 360 Watt heater.
Keep in mind you power supply has to do the bed heater, the nozzle heater, the fans, and the board. The fans and the board are small compared to the nozzle and bed heaters.
Add the bed wattage, the nozzle heater wattage, add 50 watts for the duet and fans, multiply that answer by 1.2 and that's the size power supply you want.
Opps - forgot the steppers, need to add those in too. You want to assume everything is running at the same time
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@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
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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.
