Troubleshooting bed heater
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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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