recent issue heating bed..funny smell
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@fcwilt said in recent issue heating bed..funny smell:
Did you tighten down those screw terminals every now and then?
They can loosen slightly to the point where the increased resistance of the connection can start to create some serious heat.
That may have happened to you.
Frederick
I have, I also installed a replacement board which did the exact same thing. I have a Duet wifi 1.02 and now a replacement wifi which has the blade style fuse between the two terminals. This one also would smell on bed heating and also I mentioned the blade fuse getting pretty hot. (new to me as my old board doesn't have the blade fuse there)
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I swapped out all power wires, and so far it seems to be ok. not sure if there was still some issues going on with the ground wire that has the duex5 ground or whatever but I think all is good.
I will keep checking the wire to make sure it's still going strong and not too much current on the wire. I swapped the 12g that was the pos/neg from the vin to 14g. that same 14g is on the duex5 too.
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You are exceeding the current capacity of the Duet. Go to an external relay or mosfet!
Yes I realize you might 'just' be inside the limits (didn't bother to verify) but you are no longer in a comfortable operating range. -
@gnatman said in recent issue heating bed..funny smell:
@jay_s_uk said in recent issue heating bed..funny smell:
@gnatman said in recent issue heating bed..funny smell:
16" x 16"
looking online thats going to be about 500w.
This would equate to 21amps so you're above the recommended rating for the bed mosfet (18amps).
Best to move to an external mosfetI've been printing this way for like 3 years or more. I don't think that is the issue.
Says the man who's printer smells like burning.
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@gnatman something to bear in mind is that the power draw will always be higher when the bed is heating up. It will be on full cycle while heating, whereas when maintaining temperature it will PWM control so only part duty.
Also with many resistor heaters, the resistance tends to increase a bit as they heat up, so the power draw decreases when they're at temperature.Sounds like your issue might have been in your wiring (could be some broken strands or poor contacts in your crimps?), and the fuse getting hot is probably from too high a current draw.
If you dont want to run an external mosfet (I would and do on mine!), you could at least adjust your PSU output down a bit to reduce the power. It's definitely worth thinking what will happen if/when the Duet mosfet eventually blows and fails closed
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@jens55 said in recent issue heating bed..funny smell:
You are exceeding the current capacity of the Duet. Go to an external relay or mosfet!
Yes I realize you might 'just' be inside the limits (didn't bother to verify) but you are no longer in a comfortable operating range.I'll look at adding a mosfet, do you have one you would recommend. I'm 95% sure it was just one of the neg cables screws being loose on the terminal. I didn't replace all the ends or wires the first time, I just did one side of one neg wire. then swapped the board. This time I did all of the wires.
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@phaedrux said in recent issue heating bed..funny smell:
@gnatman said in recent issue heating bed..funny smell:
@jay_s_uk said in recent issue heating bed..funny smell:
@gnatman said in recent issue heating bed..funny smell:
16" x 16"
looking online thats going to be about 500w.
This would equate to 21amps so you're above the recommended rating for the bed mosfet (18amps).
Best to move to an external mosfetI've been printing this way for like 3 years or more. I don't think that is the issue.
Says the man who's printer smells like burning.
I think it was just a cable being loose. I was able to resolve it once I replaced all the wires
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@gnatman said in recent issue heating bed..funny smell:
@jens55 said in recent issue heating bed..funny smell:
You are exceeding the current capacity of the Duet. Go to an external relay or mosfet!
Yes I realize you might 'just' be inside the limits (didn't bother to verify) but you are no longer in a comfortable operating range.I'll look at adding a mosfet, do you have one you would recommend.
Sorry, I am the wrong person to ask - I run a China SSR that is almost certainly a clone even though I know better
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after going strong for a day, it started to smell again, this time I was not home but my wife was and she stopped the printer. I purchased this mosfet https://www.amazon.com/dp/B08YZ4W4LN?psc=1&ref=ppx_yo2_dt_b_product_details
Based on the image, how do I hook this up. My heated bed has a pos/neg wire plus wires for the thermistor. I don't want to be wrong here but are the blue wires in the image supposed to be the thermistor wires or are they trying to show there is no polarity on the wires coming off the bed going to the mosfet. Im just confused slightly by the blue wires in the diagram.
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@gnatman there's no polarity coming off the MOSFET. It's just a big resistor and the cables can be used either way
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@jay_s_uk Thank you for the quick reply. hopefully this resolves the issue otherwise I'm not sure what else to do.
