Blown bed heating circuit on duet wifi
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@ageis Are you sure you're running a 100k thermistor? It would be remarkably coincidental if you happened to short out a 100k thermistor such that its room-temp resistance somehow dropped to be right in line with the 10k standard.
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@ageis said in Blown bed heating circuit on duet wifi:
I have just checked the thermistor, its reading 10k. Prusa says it shud read 100k at room temp. I felt the bed it's cool to the touch. Could this be my problem
When the bed is at room temperature, what temperature does DWC report for the bed?
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So I measured the resistance of the thermistor by measuring across the terminal next to the bed pwr output.
@Maestro
I am only going off what prusa said on their website.
It says so on this website https://help.prusa3d.com/article/heatbed-not-heating-up-properly_2086. Specifically in the measure voltage and resistence section.Plus I am very sure it would heat up to 65 degrees before and I have just checked my config, it says 100000.
M305 P0 T100000 B4138 R4700
what is the R4700 for?
@dc42 it reports it to be 20C
I can understand what @Maestro is saying. It's amazing that its work out to be a standard 10k. but my config says it's been configured as a 100k thermistor and was working till i shorted it out. I didnt know you can short out a thermistor.
I dont think murphy likes me. He's always wanting to make a fool out of me.
@dc42 why does it matter which ground I use to measure my voltages? Does the gnd for bed not end up at the vin gnd? Otherwise it wouldn't be a complete circuit, would it?
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@ageis Please unplug the thermistor from the board and measure its resistance directly, no board connections involved.
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@Maestro Ok I suppose there could be parallel resistances. It's way out of spec at 120k.
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@ageis That's not way out of spec; that's a 100k thermistor at about 21C. Now we can disregard the 10kOhm reading, and proceed on the more reasonable assumption that your thermistor is what it's expected to be and your board is reading it appropriately!
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@Maestro that's disappointing. There's potential I have broken my duet then. Am sad now.
Sorry for the confusion. I lack the experience in troubleshooting electronics.So what cud I have broken then?
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@ageis Honestly, based on the picture you uploaded (the odds of someone diagnosing a component from that image are slim) I would suggest the following.
One; remove your board from the printer and clean all the crud off of it. Honestly mate, what on earth has been done to that poor board?
Two; take a real good look for damaged components, including solder joints (bed-heater connections have clearly seen better days).
Three; reassess.
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@Maestro
Hi thanks for replying still.
I have purchased a cheap 3d printer controller off amazon. I still have issues with the bed heating up so it has led me to believe it's the bed. The bed draws half the amount of power it should draw. I want to upgrade to the magnetic bed anyway so I have brought myself prusa mk52 bed. Hopefully the issue is the bed. -
@ageis said in Blown bed heating circuit on duet wifi:
why does it matter which ground I use to measure my voltages? Does the gnd for bed not end up at the vin gnd? Otherwise it wouldn't be a complete circuit, would it?
Like other control boards, the Duet switches the negative side of the bed heater output. So the negative terminal of the bed heater output is only at ground potential when the heater is commanded to turn on. At other times it will be at the VIN potential. So if you measured 13V with the bed heater commanded off, I guess that the gate voltage was 0V and your VIN is 13V.
