MK1 heatbed question

Question for you guys...

I have a prusa , running Gen6 eletronics. ( no control for heatbed on board )

I was going to wire up the heatbed with a toggle switch to my power supply.. Any idea how how I could control the temp on the bed ?

Thanks

The easiest way would be to wire a potentiometer in series with the heated bed. Turn up the pot and you'll get a larger voltage drop over the pot and less through your heated bed, thus dropping the temperature of the bed. This wouldn't be the most efficient way of doing it since you'd be supplying current constantly and just eating up some of it in the pot, but it would be very easy to implement. Just make sure you get a pot that can handle the necessary current.

[blog.arcol.hu]

That is what I use. Replace the SSR with a normal relay. Do not run AC through the PCB bed no matter what.

Edited 1 time(s). Last edit at 03/07/2012 05:07PM by C. Cecil.

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Would something like this from my local RadioShack work :

[www.radioshack.com]

No you would need a big rheostat capable of dissipating about 100W. It isn't practical to control the bed with a "pot" alone. The simplest electronic solution would be a MOSFET to control the current driven by a comparator comparing a target value from a pot with a voltage from a thermistor circuit.

That would still only be manual control, and as I use a different temperature on the first layer, it would be a pain.

Edited 1 time(s). Last edit at 03/08/2012 08:41AM by nophead.

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[www.hydraraptor.blogspot.com]

That one can't handle enough power to work safely with the heated bed, and the resistance is probably too high to give you much useful adjustment. The more I think about it, the more I'm thinking that a pot probably isn't the best solution. It would be easy, but the power chewed up in the pot could be pretty high. To be safe, you'd want one that could handle ~150Watts. The pots that can handle that much are more expensive than the digital control boards!

A digital control board is probably your best bet. I'll think about it some more and see if I can come up with a better idea.

Doing some google work, it sounds like a lot of people have wired it right up to the power supply using 14G wire.. Looks like it heats up to 110C / 230F ...

I have a 300WATT / 30A power supply so I have enough power to run the GEN 6 board, and the PCB heatbed.. I wired it up last night and turned it on for about 10 minutes, and sure enough ... 107-12 C ..

i used 16g wire initially on my heated bed mk2 (controlled by ramps) and the wire would get very, very hot. also, the bed could only get up to about 80c due to the added resistance. replaced with heavier gauge wire and now it heats up to 110c no problem.

I use double 14 gauge wires for my heated bed, itll easily get to 140C without any issues. The wires dont get hot at all on top of that

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