Quick question, I have an issue every so often that my heated bed dies or grounds out resulting in the voltage regulator on my ramps to melt. I know the usual causes, clips digging into the heat bed, bad mounting etc.
I was curious if anyone had any kind of fail safe for this issue mainly a short circuit protection that would cut power to and from the heated bed before to much damage if any at all were caused. I was thinking a low voltage breaker but I don’t think those would act fast enough.
A gfci would work if I could find one rated at a low enough voltage.
Any ideas?
If the issue is really the MOSFET melting, a fast-blow fuse should certainly be able to blow before the electronics would.
@Jasper_Janssen I was thinking that. I like trying to make everything harder than it needs to be. 
Finally got my auto leveling setup and can’t test it. Well already until I replace that v reg. Are there any better replacements for it that you know of?
If not a fast-blow fuse, maybe some other sacrificial part? I can’t claim to have skills in circuit design, but it sounds logical. Good luck finding the cause and fixing it.
I suppose you might want to see if there is an inductance issue causing this.
I was thinking fat blow fuses and some diodes placed after the fuses or before them that allow voltage to go only one way.
Diodes are only good up to a certain voltage/current, right? You might want to consider if you are exceeding the limit or not. (disclaimer of lame electronics design here). I have blown plenty of LED’s, so that means I was probably over the limit of voltage/amps for the LED for the wrong direction. Yeah, I suck that bad. lol
I’m just going to recommend a LM2596-based buck converter, as i usually do. Adjustable output voltage, up to 3A with integrated thermal and over-current protection. They start around a buck a piece from China or four bucks a piece from a reseller in your country of choice.
Still, i don’t see how the voltage regulator would die from the heated bed shorting out - if the bed shorts, i’d expect one of the mosfets to blow or a trace to burn off.
Fix the mounting, insulate the clips with electrical tape and fit an ATO fuse of the correct amperage would be a start … cheap too
“…if you have a simple switch, switching off causes the current to fall to zero quickly, so as the magnetic field collapses, it generates a huge voltage spike that will flash across the switch contacts as they open. This is why switches/relays/contacters and transistors need to be a bit special if they are called to deal with current switching in inductive circuits. The energy stored in the magnetic field is 1/2 X I^2 X L and this energy has to dissipated somewhere, mainly as heat in the arc at the switch contacts.”
There is something to back up my idea that any coils in the design might be a cause for problem.
Put a common 1n4001 diode reverse biased across the coil to short out back EMF. Commonly referred to as a ‘flyback’ diode. This will protect switch contacts or transistors driving the coil.
@William_Frick
Cool. I hope it works for you.
Thanks for all the tips, sorry I used the wing term the heater mosfet for the bed is what goes super nova.
I replaced the bed and insulated it, rewired and did some maintenance and cable management. Now it’s running pretty good. Printing out a new x axis assembly since the one currently attached is as old as the printer, running on two years.
@NathanielStenzel put a 1k-320 ohm resistor connecting the grounds on your leds. That will keep them from blowing. Less your running a lot of current through them.