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

gplus
(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)

http://www.alirubber.com/

(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

@Chris_Brent
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!