So I’m now in the market for new controller electronics.
My only major requirements are that the heated bed mosfet can handle 15 amps and the connectors can handle the same.
Originally shared by Stephanie A
Guys, be careful or you’ll wake up to this. Luckily I smelled it and put out the fire.
yea…once you let the smoke out of those green boards they usually don’t work anymore…I’m glad no one was hurt.
I may be wrong, but I think ramps 1.4 can send 15 amps to the heated bed.
I personally really like RAMBo: https://ultimachine.com/rambo
FYI
@Josef_Prusa uses them on all his i3 builds based on the last time I talked with him a month or so ago (switched from RAMPS 1.4).
@Benjamin_Veenema the Ramps design doesn’t have large enough traces for such loads, be carefull when doing that
Rambo ftw
Wow! Glad you’re okay!
I may have to put a smoke alarm on my printer when I get it.
@Carlton_Dodd melted ABS may set off the alarm during normal operation.
@J_Brad_Harris Thanks for that. Might have to do heat, or even current sensing. I suppose appropriate fusing would be helpful.
I know, of course, that this will not happen for a while after I get my printer; I’ll be sitting in front of it all night, mesmerized, for the first month or so. 
Another reason why I use a silicone heater pad on 110v with a solid state relay. =D
Expensive, but it means the controller doesn’t need to push much through the SSR. The risk of fire comes more from shorting something out…
Don’t sleep and print.
+1 for silicone heating pad. Just better.
@Matt_Miller I mean, there are some drawbacks. Like working with 110v, having to use an aluminum build plate, and the setup required in order to mount it all, but you are not kidding that in the end, it’s totally worth it. Maybe I should sell kits for this. =D
I made the switch and never looked back. 110V is the way to go. You just have to be comfortable with AC and take some very basic precautions. Add to that I can now go from cold to printing ABS in about 2 minutes.
12x12 piece of 0.04" aluminum sheet. Set a sticky-backed silicone heating pad to the bottom. Bulldog a piece of mirror glass to the top. I took 3 nylon standoffs and a M5 countersink bit and bored them out so that an M5 flathead screw would countersink flat into the standoff. After tapping the standoff I drilled a 5.5mm hole in the aluminum where I wanted the standoff to go and screwed the M5 flathead screw into the standoff, sandwiching the aluminum plate between the head of the screw and the standoff. Since Aluminum is so flexible it deformed right into the countersunk hole. Then it was just add some M5 allthread to the bottom of the standoffs and into the Y-axis drive stage. I’ll post a pic when I get a chance. And wiring the SSR is very easy.
The assembly
The screw removed
Lifted
I’ve got no real strain relief, which is something that I should do given the voltages concerned. However, the leads coming off the silicone pad are quite robust, and they’re only rubbing on smooth extruded aluminum, so not too worried about wear (famous last words).
And the plate is slightly deformed when tightening the screws down. But since I’m just clamping a piece of glass to it I really don’t care all that much, so long as the glass is orthogonal to the nozzle (which it is). 
I got a 40 amp SSR n amazon for 20 bucks. I’ll admit that running only 7 amps gets it decently warm, but you can easily pick up a cheap heatsink. It’s also a simple upgrade to 110 ac as most ssr’s handle both. I can simply use the 12vdc heater output to trip the relay. I would not trust running 15 amps through a controller board, too many points of failure and that’s a LOT of current. Glad you’re OK. Once you shock yourself a couple of times you realize 110 vac really isn’t a lot. And you can buy 10 dollar inline gfci plugs for added safety, but the ac heater pads are designed for this
@Eric_Moy safety should be your number one concern. After waking up to my printer on fire, I now know that I should not skimp on safety.
Right now I’m thinking about retiring the Teensylu board and redesigning it. The printrboard likely won’t have this issue due to the 2oz/in copper, however the connectors are still a point of failure. I already did some searches and found some connectors capable of 10 amps, though I might opt for even higher ratings than that. I’ll likely run 2 connectors in parallel.
Finding a vendor who will make a small qty of 4 layer 2oz/in boards will be a hassle though.
I went a completely different route. I went with 1/8 inch thick (3mm) aluminum plate, 9"x9", with a 6"x9" silicone heater pad, and took my bed plate, clipped it to the aluminum, scribed some drill holes, drilled them out and countersunk (90 degree countersink) them for flatheads. Then used this as my bed material, flathead screws so they sit flush under the glass. The glass is 9"x9" clipped to the top plate, the silicone heater pad is attached using some high temp silicone adhesive under the aluminum plate (same stuff the mat is actually made out of) and wired at the back of my printer. I’m close to a place called Skycraft and they sell 20A SSRs for like $15 a piece, but the bed only pulls something like 5A from the wall (and not your electronics) so well within the range of the SSR. It’s a 540 watt heater pad, and has a max temp of 200C, so the thing is a beast. I have it sufficiently insulated on the underside and the thing hits 110C SO fast and doesn’t struggle at all.
I got my alum plate here: http://www.onlinemetals.com/merchant.cfm?pid=1246&step=4&showunits=inches&id=76&top_cat=60 (Make sure you use the custom-cut and get a 9"x9" plate)
and the heater pad I’m using here: http://www.mcmaster.com/#35765K29
Solid state relay here: http://www.skycraftsurplus.com/relaysolidstatedccontact.aspx
But…this is all obviously an option AFTER you’ve procured new electronics, and you probably want to have access to someone with a drill press.
@Stephanie_A I was mentioning the 110vac route as a safer method. Higher current is more dangerous in terms of for as it hearts up your components faster. Also, the parts used in @ThantiK design above are all rated well above what it will be used for in a 3d printer, as they are designed for much more demanding uses. I really would not feel safe trusting the traces and solder joints on a hobby printer board with such safety critical current, bit I’m kind of paranoid with fire. I’m currently using pretty low current 12vdc and have done the good old touch test on all my components. They get warm but easily touchable. I only go to 62c for plan though. I plan to copy Anthony’s heated bed setup once I get around to it… And get some more money in my hobby budget. These little upgrades add up fast. 110 vac is just as safe as 12vdc as long as you respect insulation ratings on parts and keep your connections covered/insulated. But again, I’d trust the insulation on that McMaster heating pad over the solder joints on a board anyday. Adding a GFCI would also be a good idea. Good luck
