Troubleshooting bed heater
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That all looks right.
Do you have a blade type fuse between the power in connector and the bed heater connector?
Measure the voltage between the power in connector GND terminal and the bed heater connector VIN terminal.
Frederick
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@Veti the heated bed was working with the stock MKS gen 1.4 board.
I upgraded the firmware on the duet before setting it up so I did not try the heated bed with the older firmware.
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check the fuse on the board
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@fcwilt well now I feel just a little dumb.. The fuse is the issue.
Now I wonder what should be done moving forward? I know the black widows started shipping with an external mosfet at some point after I purchased mine but I never installed one. I read some posts from other black widow users on the forum that didn't seem to think the external mosfet was necessary, but if I tripped the fuse presumably on the first attempt at heating the bed I wonder will it be safer to install an external mosfet?
Thanks for the help.
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@Dee_Pee
measure the resistance of the bed. -
Well do you know how much current the bed heater is supposed to draw?
If you don't can you measure it's resistance?
Frederick
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I do not know off hand how much current it is supposed to draw but I am measuring 1.4 ohms on the bed.
I'm linking below to a bed heater that is sold as a replacement for the black widow but I think this one would be an upgrade for my machine which is likely part of the issue at hand. My widow is an early version that came with a PCB heatbed and before they started shipping with the mosfet, as I said before. The stock connector that came with the kit has always been a little shoddy with voltage and ground split over four wires. There was a reason they started shipping them with mosfets afterall. I know one popular mod is to solder the wires directly to the bed for a better connection so I will start there but I wonder if I should still plan to add a mosfet if I want to use my current heated bed with the Duet.
I was able to run a PID autotune and heat the bed up 90C without burning out the new fuse, however each subsequent attempt at heating the bed has so far resulted in a fault.
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If you power supply is 12V you are OK with that heater - if 24V then you need an external device of some sort.
What sort of fault are you seeing?
Frederick
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I am using a 24V PSU so I will plan to add the fet while I am doing my other upgrades.
The faults stated the bed was not heating as fast as expected.
Thanks for the help!
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@Dee_Pee said in Troubleshooting bed heater:
I am using a 24V PSU so I will plan to add the fet while I am doing my other upgrades.
The faults stated the bed was not heating as fast as expected.
That's strange - with 24V power it should heat up just fine.
To verify are you using PID mode?
Frederick
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@fcwilt Yes, I am using PID mode. After replacing the fuse it did heat up just fine the first time and sustained a temp around 90C to complete a PID autotune. I received the faults when I then tried to run off a print afterward.
I've soldered the wires to the bed and was able to heat it again and begin a print. I suspect the issue was probably due to the cruddy connection where the wires enter the bed probably adding a bit of resistance there. My bed and hot end sensors now give matching readings at room temp whereas before they were at least a few degrees apart so this theory seems to check out so far.
Thanks again.
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