Anyone using the 18" X 18" Monster Heatbed MK1 PCB?

I just got the 18" X 18" Monster Heatbed MK1 PCB but it didn't come with any instructions. I already figured out how to mount it and keep it flush with a glass top. I just don't know if this can be controlled by the Gmax printer and how many ams I need for the 12V power source (Or which is the positive and which is the negative).

Is anyone using this? It looks nice but it talks about LEDs on the front and I don't have any LEDs. Any advice would be appreciated. Thanks!
I can't speak to the amps required for it to run but I can speak to the LEDs if it is based of the MK1 specifications on the reprap wiki. The LEDs are entirely optional, they are only there as passthroughs not essential to the circuit. They are there to tell you when the bed is on and hot, as a safety feature. Without them the bed will operate normally just be careful to know when the bed is on because you will have no notification other than your software telling you (or holding your hand above the bed to feel the radiation heat).
Thanks for the info. Yes, there are no LED on this board. They just wrote that. Lame. For anyone else's info, it's 12vdc that needs about 50 amps. I was suggested a dedicated 600w power supply. Unless I get a 50 amp relay somewhere, I don't think I can hook it to the Gmax. It would be nice if it was controllable. Seems to take quite a bit of energy to run this thing!
Justin, you've got the right idea. I would use a dedicated power supply just for the peace of mind that the monster heatbed isn't going to trip a fuse on the control electronics or something of that sort. It's possible.

Mechanical relays can't keep up with PWM (pulsing on and off at some moderate to high speed, which is how the target temperature is maintained in all the heating elements). What you'll want, ideally, is an optical isolation relay, also referred to as a solid state relay. A transistor or mosfet would work as well, but I'm recommending to completely isolate the 2 circuits from each other.

Quick primer:

From taking a look, it seems that an opto isolator relay of the amperage you are requesting will be expensive. Where did you get the 50 amps number from?
Augh. I think I'm going to have to look into that relay isolation another time. My concerns is the monster board takes quite a bit of juice, and I'd rather it turn off once the print is over automatically. I'd hate for it to keep running for no reason.

I called Jim, the guy who makes the monster board. His number is in the ebay description. He says they've only sold maybe 20 of them. First he said get a 500w power supply. 600w if I know it was going to be running for long periods. To connect the power supply to both sides of the board to make sure heating was even. When I pressed him for amps he said 50. We discussed using the 1" on sides to drill holes since there is nothing there. I don't think it's necessary thought.

Hey, if you can walk me through it I might try that relay isolation. But I also have a 8.5x8.5 inch heatbed around me. Maybe I can attach that as a test?
Well based on the fact that the same seller offers this:

Let's give mechanical relays a shot after all. The PWM I've seen on my extruder isn't all that fast, so this may work. Now that I think about it, it should.

Now, $20 for a relay on a circuit board with screw terminals is overpriced. I'm sure you can search that model # and get the relay itself for a few bucks, but the completed product will make your life easier.

The electromagnet contacts on the relay will attach to the 3D printer control board. Then, you will use a separate power supply to power the board with one of the connections going through the relay.
I'm going through the same process. Ordered and installed the 18x18 MK1 PCB heated bed. The 30 Amp Relay board will arrive in about a week or so.

Until then I'm sitting waiting...



You might wanna call the guys who sells these. You need at least a 50amp from what he's told me. I spoke to the guy directly and he told me the 30amp relay they sell doesn't work for these.

Interesting. Jury is still out if these guys are incompetent or malicious. Although I've encountered more than my fair share of the latter, Occam's razor reminds me to never attribute to mal-intent what can be explained by simple incompetence. :)

Will give them a call. Thanks for the info!
Does anyone know where the two relay control wires should be attached to the RAMPS board?

I'm guessing not D08 terminals used to power the smaller heat bed on my other printer.

If you have dual extruders, you can put it instead of the cooling fan, but you'll lose the fan capability and have to use a fan extender to get it back.

If you only have a single extruder, you should have a free port in the screw terminal region there.

Either way, you will have to make 1 or a few small changes in the firmware Configuration.h file.

Remember to put a diode across the relay terminals backwards to prevent electromechanical blowback!