Connecting heated bed to electronics just wondering how people are connecting heated beds to there electronics? from my research i see that the bed takes just under 7A of power now heres were i see problems the header and pin connection are only rated at 3A even splittling them like the Sanguinololu does over 4 pins instead of 2 only gives 6A then the other problem i see is the wire needed does not support the crimp connectors correctly. im thinking its safer and cleaner to build a small board and run the heated bed separate to the board. https://reprap.org/forum/read.php?1,149620,149620#msg-149620 Tue, 14 Jul 2026 11:27:43 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,149620,149974#msg-149974 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149974#msg-149974
Anyways, it's history. Gen7 v1.4.1 is out. With a MOSFET so much oversized, making even the heatsink obsolete.]]> Traumflug General Thu, 23 Aug 2012 10:38:13 -0400 https://reprap.org/forum/read.php?1,149620,149949#msg-149949 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149949#msg-149949
Logic drive fets specify the RDSon at 4V and have a max gate threshold around 2V to achieve a reasonable figure at 4V. The only reason your IRFZ 44Ns work is luck that you haven't encountered the worst case yet. You see people in these forums that are less lucky and report that their MOSFET melted.

Why do you think logic drive FETs exist if it is fine to use ordinary ones with logic?]]> nophead General Thu, 23 Aug 2012 08:40:55 -0400 https://reprap.org/forum/read.php?1,149620,149943#msg-149943 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149943#msg-149943
Quote

The FET on my Sanguinololu gets quite hot but survives.

As does the IRFZ 44N.

I mean, I've put quite a bit of research into this issue and for me it's simply impossible to destroy this type with an 8A current sink. The data sheet says 4.0V (worst case) are sufficient for switching. Similar types with a lower gate voltage behave about the same. I'd appreciate to see measured facts if one disagrees. :)

That said, applying the Gen7 v1.4.1 upgrade to the SevenSwitch is the obvious next step.]]> Traumflug General Thu, 23 Aug 2012 07:33:06 -0400 https://reprap.org/forum/read.php?1,149620,149914#msg-149914 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149914#msg-149914
The current rating of the MOSFET is largely irrelevant as you would struggle to find a low voltage TO220 MOSFET rated at less than10A these days. The important things is RDSon at Vgs a bit less than 5V. That determines how hot it gets.

IRFZ044 is not a logic drive FET so not guaranteed to have low RDSon when driven from 5V. The FET on my Sanguinololu gets quite hot but survives. The ring terminal and thick wire I use take some of the heat away. A heatsink would be a good idea. Better still replace it with a logic drive MOSFET.

.]]> nophead General Thu, 23 Aug 2012 04:20:26 -0400 https://reprap.org/forum/read.php?1,149620,149880#msg-149880 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149880#msg-149880 xiando General Wed, 22 Aug 2012 22:21:18 -0400 https://reprap.org/forum/read.php?1,149620,149864#msg-149864 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149864#msg-149864
Quote
nophead
I wired 12V direct from the PSU to the bed and connected the other bed lead to the tab of the MOSFET using a ring terminal.
]]> Andrew Smith General Wed, 22 Aug 2012 19:48:33 -0400 https://reprap.org/forum/read.php?1,149620,149827#msg-149827 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149827#msg-149827
I think nophead was referring to the use of an offboard switching solution, like the SevenSwitch PCB that Traumflaug noted above. (The IRFZ044 is rated at a far higher max current and voltage than is used for the heater, so it should be VERY solid.]]> xiando General Wed, 22 Aug 2012 17:38:53 -0400 https://reprap.org/forum/read.php?1,149620,149823#msg-149823 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149823#msg-149823
if so can we get an diagram of this on how to wire it up]]> Enlightx General Wed, 22 Aug 2012 17:13:13 -0400 https://reprap.org/forum/read.php?1,149620,149795#msg-149795 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149795#msg-149795 forums.reprap.org]]]> nophead General Wed, 22 Aug 2012 14:04:54 -0400 https://reprap.org/forum/read.php?1,149620,149780#msg-149780 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149780#msg-149780
i dont think ramps has a problem as its has correct terminal headers

Sanguinololu electronics are okay and fine its just the connections which are the problem the connectors cannot take that many amps safely.

ideadly we could do with a 12v reading mosfet which then handles the output to save modding the board.

for techies its easy enough to mod the board and solder wires and put the Sanguinololu mosfet to terminals but would be nice to have a simple plug in solution.]]> Enlightx General Wed, 22 Aug 2012 12:20:24 -0400 https://reprap.org/forum/read.php?1,149620,149755#msg-149755 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149755#msg-149755 brnrd General Wed, 22 Aug 2012 08:47:41 -0400 https://reprap.org/forum/read.php?1,149620,149716#msg-149716 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149716#msg-149716
Quote

in reality they should of designed the baords so that the mosfet was not on the board and on a smaller inline board with decent 10A terminal connectors to be safe.

This reality: [reprap.org] ?]]> Traumflug General Wed, 22 Aug 2012 04:44:53 -0400 https://reprap.org/forum/read.php?1,149620,149683#msg-149683 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149683#msg-149683 rcs General Wed, 22 Aug 2012 02:45:04 -0400 https://reprap.org/forum/read.php?1,149620,149671#msg-149671 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149671#msg-149671 a printed board, as long as the subcircuit
- uses a dedicated and isolated supply line (so you're not forced into sharing the power supply for the processor/etc with that of the heater)
- has sufficiently large traces that are properly placed on the board
- uses a sufficient FET for the purpose (imo over-engineered rather than marginally)
- provides sound thermal management constraints for the FET (sufficient room for a heat sink and/or edge mounting so it can be attached to an enclosure wall)
- uses proper termination at the user interface (ie large enough screw terminals or connectors, both to accept the wire and to *comfortably accommodate the current).

There are a couple of additional things I might do were I to design a board, but that covers the lion's share.

Based on the boards used by this community that I've seen so far, I tend to agree that an offboard temp controller might be a good idea, at least for the bed heater.]]> xiando General Wed, 22 Aug 2012 01:50:19 -0400 https://reprap.org/forum/read.php?1,149620,149640#msg-149640 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149640#msg-149640
I've been using the Azteeg X1 and it works quite well with small heat sinks on the MOSFETS. I'm about to test the Azteeg X3 which uses lower resistance MOSFETS so it doesn't need as much heat sink.]]> brnrd General Tue, 21 Aug 2012 18:45:43 -0400 https://reprap.org/forum/read.php?1,149620,149632#msg-149632 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149632#msg-149632
might have to look into deeper into doing this as iv already had a connector melt from too much power.

just for notes when i got an ameter on my heated bed i was getting 6.8A from cold. But was using very thick wire so might of knocked the power draw down.

looking at the ramps board it uses the correct terminal pins for both extuders and also heated bed.

its starting to make sense now why the Sanguinololu comes in much cheaper.]]> Enlightx General Tue, 21 Aug 2012 18:07:48 -0400 https://reprap.org/forum/read.php?1,149620,149628#msg-149628 Re: Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149628#msg-149628
I wired 12V direct from the PSU to the bed and connected the other bed lead to the tab of the MOSFET using a ring terminal.]]> nophead General Tue, 21 Aug 2012 17:55:34 -0400 https://reprap.org/forum/read.php?1,149620,149620#msg-149620 Connecting heated bed to electronics https://reprap.org/forum/read.php?1,149620,149620#msg-149620
from my research i see that the bed takes just under 7A of power

now heres were i see problems

the header and pin connection are only rated at 3A

even splittling them like the Sanguinololu does over 4 pins instead of 2 only gives 6A

then the other problem i see is the wire needed does not support the crimp connectors correctly.

im thinking its safer and cleaner to build a small board and run the heated bed separate to the board.]]> Enlightx General Tue, 21 Aug 2012 16:54:26 -0400