Has anyone purchased this 12V heater mat from RobotDigg?  http://www.robotdigg.com/product/209/200mm+Silicone+Rubber+Heater+Pad I assumed I could

(Chirag Patel) #1

Has anyone purchased this 12V heater mat from RobotDigg?

I assumed I could plug this into my RAMPS board like a standard heated bed but the large polyfuse on the board got very hot and stopped powering the mat. Should I try modding my board and replace the polyfuse with a wire? Would I be able to run this mat on 120V with a SSR?

(Eric Lien) #2

No the resistance would be off to run it at 120v AC. I recommend you get a 120V heater even though I think that’s not the answer you want to hear.

(Chirag Patel) #3

And 30 minutes after posting this I realized I had the bed hooked up to the wrong port on my RAMPS board. I was running the bed off the extruder heater port and was tripping the small polyfuse not the large one. Problem solved and this mat is working perfectly.

(Eric Lien) #4

I have been using the 120V AC silicon heater mats from Alirubber on Aliexpress for a long time. They have always performed great for me. Cost is only like $35 and you can specify everything you want about them and they are built to order. I made mine for HercuLien 800W, 120V, 380X380mm, dual thermistors (in case one failed), 1.5M cable length for routing to the SSR.

I always talked directly with Daisy Huang (daisyhuang “at” http://alirubber.com.cn)


(dstevens lv) #5

The poly fuses on the lower cost RAMPS sometimes aren’t up to spec. You can try to replace it with a like rating (specs in the reprap wiki for RAMPS) or replace the fuse entirely with an automotive type fuse and holder.

(Ted Huntington) #6

Chirag- how long does the 12V mat take to reach 120C- have you tried that?

(Chirag Patel) #7

@Ted_Huntington I’m not sure. After I fixed my problem I ran a PID autotune to 90C which seemed to have heated up a lot faster than my other printer’s MK2 heater bed. I’m about to mount my mat and a sheet of PEI to my aluminum bed so I’ll see if I can run some timed tests tomorrow.

(Ted Huntington) #8

@Chirag_Patel I use 120V (the mains in the US) and for a 300x300mm 500w heating pad it usually heats up to 120C in under 10 minutes, and I wonder if the 12V version can heat up that quickly with 12V.

(Kevin Conner) #9

@Chirag_Patel , I recommend wiring your 12v positive lead directly to your power supply. wire the negative leat to the RAMPS for switching. This bypasses the fuse and all those tiny little circuits. I did this more than a year ago for all my heaters by recommendation from a #reprap irc member and it’s solved all the polyfuse problems inherent to the RAMPS.

(Jim Stone) #10

If you do that you MUST put a fuse inline so it stays fused otherwise thats dangerous

i run mine like that. i completely removed the fuses and run better blade fuses. the poly fuses are trick finicky things and like to just fail.

another thing i did was removed the stupid main power connector and hard wired it to some powerpole connectors. much better.

(Kevin Conner) #11

Yes. Add a fuse. I should have included that.

(Jeff DeMaagd) #12

The cheaper RAMPS polyfuses might be OK with 12V. At 24V it might be an issue because sometimes the assembler cuts corners and uses 16V polyfuses.

I did the Alirubber route too. Custom built to a custom layout per blueprint. Wiring length & type to request. Added a second thermistor for free or $1 more (I forget). Did dual voltage to my request too, rewire it from parallel to series to work with double the voltage. I bought a spare heater incase I screwed up the first. I think it took them 3 days to fabricate. It’s been working great, but maybe only 50 hours of power applied so far.

(Chris Brent) #13

@Eclsnowman Do you run the printer power supply and the heated bed on the same house circuit. What does an 800W heater plus a the printer power supply get for its peak current? My math can get to 20 amps, but I don’t think switching power supplies work they way I think they do. i.e. Does a 24V DC, 400W power supply pull 16.66 amps from the supply side? And if not, how do you get to 400W. I guess I’m asking, how big can you go on your heater in Watts?

(Jeff DeMaagd) #14

What is your mains voltage? If 120VAC, the bed takes 6.7A peak. It’s only full on for warmup. The rest of the 3D printer probably only adds another amp, so I would say maybe 8A peak for planning. Average current might not even be half that when it’s up and running.

(Chris Brent) #15

Yeah 120VAC. Just wondering what the worst load case could be.

(Eric Lien) #16

Yeah, on my HercuLien I was running the bed at 24V originally. Hence why I have such a high power PSU on it. But to be honest now that the bed runs at mains a 250W would more than take care of two 40W heaters and 5 steppers.

(Chris Brent) #17

So I also got concerned because I lived most of my live in 240VAC countries, which usually have 10 or 11 Amp fuses. I only just realized my circuit breakers here in 110VAC land are 20 amp!