RAMPS Fuse/MOSFET extremely hot, shut off print bed
Posted by mklinker
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Re: RAMPS Fuse/MOSFET extremely hot, shut off print bed December 17, 2013 01:18PM |
If you only have 7A into your heated bed, something is indeed wrong. Check the voltage at the bed terminals when it's trying to warm up. You should have ~ 11V. If it's way less, you need to find and fix the problem.
If you have a significant drop on the PTC fuse, chuck it and put in a 15A auto fuse externaly. Run the heated bed hot end directly through it to the power supply. (note the qualifier *through* the fuse
).
If you have a significant drop on the PTC fuse, chuck it and put in a 15A auto fuse externaly. Run the heated bed hot end directly through it to the power supply. (note the qualifier *through* the fuse
).
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Re: RAMPS Fuse/MOSFET extremely hot, shut off print bed June 15, 2014 07:29AM |
Just thought I would pop in an update on my heatbed issue. I got an IRF405 mosfet from Jaycar today and put that in place of the other mosfet feeding D8 and now I have a mosfet that runs cool and I get around 10.6 V to the heatbed which allows it to warm up to 110deg in just under 20min.YAY Now printing and finding out how much calibration I need to do to get my printjobs looking good. 
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Re: RAMPS Fuse/MOSFET extremely hot, shut off print bed June 20, 2014 10:10PM |
Sorry for the ddelay in getting back to you cdru. I have taken the effort to measure the resistance of the heatbed and found it to be approx 1.5ohms when it was sitting at 60deg between prints (this printing is so addictive.
The voltage at the bed just after connect wires and turning it back on is approx 10.31V now with 3.8A current being measured to the bed via a clamp meter for current measurement. The Voltage at the supply terminals ia approx 11.45V. My suspicion is now leaning on the PS not being able to keep up. So, do I go for a 24V system or a new 12V supply. If I go for the 24V supply, what do I need to change as far as parts go? I know I will have to change the wiring of the bed. I am sure the MOSFET I put in is OK for 24V as well. All comments welcome.
The voltage at the bed just after connect wires and turning it back on is approx 10.31V now with 3.8A current being measured to the bed via a clamp meter for current measurement. The Voltage at the supply terminals ia approx 11.45V. My suspicion is now leaning on the PS not being able to keep up. So, do I go for a 24V system or a new 12V supply. If I go for the 24V supply, what do I need to change as far as parts go? I know I will have to change the wiring of the bed. I am sure the MOSFET I put in is OK for 24V as well. All comments welcome.
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Re: RAMPS Fuse/MOSFET extremely hot, shut off print bed July 02, 2014 06:04AM |
Yes @cefiar, you are totally correct in the power calcs.....lol....I am really out of practice on these....must stop trying to do calcs in the middle of the night....
Gave myself a good smack in the head after that dumb mistake.
Thanks again for your valuable advice. I have a Battery charger I built as an apprentice, I may have a closer look at it in the morning to see what sort of current I built it to handle.(it was a long time ago after all...hee hee) I am sure it has a voltage output greater than 13V as it was built to charge car batteries.
Will get back to everyone with the results very soon now I am back from a my break in the snow.
regards
Nige
Gave myself a good smack in the head after that dumb mistake.Thanks again for your valuable advice. I have a Battery charger I built as an apprentice, I may have a closer look at it in the morning to see what sort of current I built it to handle.(it was a long time ago after all...hee hee) I am sure it has a voltage output greater than 13V as it was built to charge car batteries.
Will get back to everyone with the results very soon now I am back from a my break in the snow.
regards
Nige
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