Heatedbed 12V 300W - Help Hello Folks I bought a 12V 300W silicone heater from Robotdigg and im trying to make it work but im getting some trouble with it. First of all i bought 2 SSR relay's, a fotek 25dd and 40dd , DC DC SSR. I have burned down both relays. Now i have changed the Mosfets inside to a P55NF06 like the ones mounted on the extra Ramps 1.4 i had laying around. Now i have then attached a big alu heatsink but it doesnt do the job well, because the relay works and i can get to the desired temperature at 95-100 degrees. But thats only possible if i wait 40 mins for it to reach it. And the heatsink is untouchable. So my question is, how come i meet this problem it doesnt seem others need a heatsink that big. (See this link: [imgur.com] ) :( Thanks in advance. https://reprap.org/forum/read.php?1,592563,592563#msg-592563 Tue, 19 May 2026 15:30:28 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,592563,594161#msg-594161 Re: Heatedbed 12V 300W - Help https://reprap.org/forum/read.php?1,592563,594161#msg-594161
I do like the Reprap.me's power extender but i do not intend to buy from them.

So now im wondering if i just should buy the AC Heater and try out a SSR AC.

But thanks guys for the answars :)]]> TRoager General Tue, 08 Dec 2015 03:27:58 -0500 https://reprap.org/forum/read.php?1,592563,593889#msg-593889 Re: Heatedbed 12V 300W - Help https://reprap.org/forum/read.php?1,592563,593889#msg-593889 Putzer General Mon, 07 Dec 2015 09:48:59 -0500 https://reprap.org/forum/read.php?1,592563,593398#msg-593398 Re: Heatedbed 12V 300W - Help https://reprap.org/forum/read.php?1,592563,593398#msg-593398
reprap_me

Admittedly my printers' heatbeds are 140W each, not 300W, but these boards do have a considerable current-carrying capacity (do read the spec for more details). Even when taking a heatbed to 110C the board's components barely get above 'warm to the touch'. Note that I didn't use the optional screw connectors - I soldered the cables directly to the solder pads (recommended for higher currents).

The supplier is based in Copenhagen, Denmark so may not be convenient - but they are pretty good at delivering overseas.]]> David J General Sun, 06 Dec 2015 04:58:01 -0500 https://reprap.org/forum/read.php?1,592563,593381#msg-593381 Re: Heatedbed 12V 300W - Help https://reprap.org/forum/read.php?1,592563,593381#msg-593381 Don't remember the name, but this will for sure be cheaper than a high end SSR and has low voltage drop.

Can someone jump in with details/links :)
-Olaf]]> o_lampe General Sun, 06 Dec 2015 04:37:03 -0500 https://reprap.org/forum/read.php?1,592563,593286#msg-593286 Re: Heatedbed 12V 300W - Help https://reprap.org/forum/read.php?1,592563,593286#msg-593286
Quote
TRoager
But how come others can måske it work and not me :/?

They don't, unless they are using good SSRs with low voltage drop. There are several other posts on these forums reporting exactly the same problem.]]> dc42 General Sat, 05 Dec 2015 18:45:49 -0500 https://reprap.org/forum/read.php?1,592563,593253#msg-593253 Re: Heatedbed 12V 300W - Help https://reprap.org/forum/read.php?1,592563,593253#msg-593253
I have now tested and measured a bit.
First off, i have a Fluke 179 and measured with the thermocouple i got with it. Seems to be in order with the thermistor in side the silicone heater.

There are 2.3V over the SSR relay (MOSFET)
And 10.2V over the heated bed.
12.5V on the PSU.

So yes im not getting full 12V on the heated bed. The bed i have measured to 0.5Ohm

I have talked to robotdigg and they are willing to replace my heater for an AC bed. But it costs quite alot to ship it to China :(

But how come others can måske it work and not me :/?]]> TRoager General Sat, 05 Dec 2015 15:40:49 -0500 https://reprap.org/forum/read.php?1,592563,592633#msg-592633 Re: Heatedbed 12V 300W - Help https://reprap.org/forum/read.php?1,592563,592633#msg-592633
Second, for any printer with a bed size greater than about 200 x 200mm and a heated bed that isn't driven from AC mains, it's much better to use 24V power than 12V. This halves the current to the bed, so that a Duet or other good electronics board can drive a 300W heater directly, without needing an SSR.

The easy but expensive solution to your problem is to replace the SSR by a decent one with low voltage drop, e.g. Crydom DC100D40 costing about $100.

A less expensive solution that may work is to use one of these [reprap.me]. It's essentially a 5-terminal SSR. The 25A current that your heated bed draws is a little more than I would be comfortable with; it will dissipate about 5W of power and get quite hot. You could connect two in parallel if need be.]]> dc42 General Fri, 04 Dec 2015 04:51:20 -0500 https://reprap.org/forum/read.php?1,592563,592594#msg-592594 Re: Heatedbed 12V 300W - Help https://reprap.org/forum/read.php?1,592563,592594#msg-592594
Did you check the wiring and PSU for voltage drop?
Is the wire gauge sufficient?
Did you verify the thermistor with a second ( known ) one?
-Olaf]]> o_lampe General Fri, 04 Dec 2015 03:36:26 -0500 https://reprap.org/forum/read.php?1,592563,592563#msg-592563 Heatedbed 12V 300W - Help https://reprap.org/forum/read.php?1,592563,592563#msg-592563
I bought a 12V 300W silicone heater from Robotdigg and im trying to make it work but im getting some trouble with it.

First of all i bought 2 SSR relay's, a fotek 25dd and 40dd , DC DC SSR.

I have burned down both relays.
Now i have changed the Mosfets inside to a P55NF06 like the ones mounted on the extra Ramps 1.4 i had laying around.

Now i have then attached a big alu heatsink but it doesnt do the job well, because the relay works and i can get to the desired temperature at 95-100 degrees.
But thats only possible if i wait 40 mins for it to reach it. And the heatsink is untouchable.

So my question is, how come i meet this problem it doesnt seem others need a heatsink that big. (See this link: [imgur.com] ) :(

Thanks in advance.]]> TRoager General Fri, 04 Dec 2015 00:40:28 -0500