Heated Bed Issue I am trying to get my heated bed working with Ramps 1.4 & Marlin. Bed came from Sainsmart and is the 12/24v version hooked to D8. I have a big power supply set to 12v on both power in points. Thermistor is reading room temp connected to T1. LC display shows B020/060. So it is showing temp should be at 60. However, I get zero voltage out of D8. This is a new printer and the heated bed has never been hooked up. I think the mechanics are hooked up correctly. Marlin: #define PIDTEMPBED #define BED_LIMIT_SWITCHING #define MAX_BED_POWER 255 I don't know where to go from here. Help please. https://reprap.org/forum/read.php?219,289361,289361#msg-289361 Wed, 12 Aug 2026 16:27:36 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?219,289361,296184#msg-296184 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,296184#msg-296184 rcazwillis RAMPS Electronics Thu, 16 Jan 2014 23:06:38 -0500 https://reprap.org/forum/read.php?219,289361,296181#msg-296181 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,296181#msg-296181
If you're staying under 30V (which is 99.99% of people) then I suggest something like the IRLB8743. Handles higher current, has a lower Rds(on) (= more volts to your heated bed), etc. It's used on RAMPS-FD and on other electronics like Gen7.

[www.irf.com]

BTW: The IRLU8743 is almost identical to the IRLB8743.

Both devices are pin-out compatible with the STP55NF06L (so you just solder it in the exact same way).

Numerous electronics places sell them, so it'll depend where you're located as to what is convenient to you.

eg:
Digikey have the:
IRLB8743 for US$1.42 (at time of posting)
IRLU8743 for US$1.60 (at time of posting)

Note: I did look at E14/Newark, but their US site seems to not have the range the AU site does, which is a pity.

PS: The forum seems to be mangling the links, which is why I had to edit things. It "works" though the links are still not what I entered.]]> Cefiar RAMPS Electronics Thu, 16 Jan 2014 22:46:36 -0500 https://reprap.org/forum/read.php?219,289361,296144#msg-296144 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,296144#msg-296144 rcazwillis RAMPS Electronics Thu, 16 Jan 2014 20:53:10 -0500 https://reprap.org/forum/read.php?219,289361,294624#msg-294624 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,294624#msg-294624 AlexNZ RAMPS Electronics Tue, 14 Jan 2014 12:38:11 -0500 https://reprap.org/forum/read.php?219,289361,294446#msg-294446 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,294446#msg-294446


looks like top one is 11 and bottom is 5 amp...
]]> AlexNZ RAMPS Electronics Tue, 14 Jan 2014 06:28:53 -0500 https://reprap.org/forum/read.php?219,289361,294354#msg-294354 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,294354#msg-294354
Most ramps the first polyfuse is much larger than the second one..

eg

Are you sure yours are the correct way around? if not you have the 5amp fuse on the 11amp rail...
]]> Dust RAMPS Electronics Tue, 14 Jan 2014 04:10:01 -0500 https://reprap.org/forum/read.php?219,289361,294311#msg-294311 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,294311#msg-294311


and i don't understand why green led on heated bed not lit
]]> AlexNZ RAMPS Electronics Tue, 14 Jan 2014 02:28:49 -0500 https://reprap.org/forum/read.php?219,289361,294302#msg-294302 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,294302#msg-294302
Also: Make sure that they're not actually touching each other.

They work by heat and will trip once the internal temp gets to a set value. The PTC fuse issue is a flaw in the design of RAMPS. If I use a RAMPS board for a printer, I personally replace them with thick wire, then put proper fuses in-line between the PSU and the RAMPS board. They're flaky, annoying and in the case of very high current shorts, dangerous (they can actually catch fire). They also take a very long time to trip (>20 seconds) which makes debugging a fault annoyingly hard.]]> Cefiar RAMPS Electronics Tue, 14 Jan 2014 02:02:06 -0500 https://reprap.org/forum/read.php?219,289361,294290#msg-294290 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,294290#msg-294290 seems that i have the same issue here
recently i finished assembly my delta-Mendel printer and when i turn printer on and tell prointerface to print, or heat bed to 110° it start to heat bed, but when thermistor shows about 40° - voltage on D8 goes from 12V to 0 resulting in heated bed stops heating (it goes by inertia up to 60° but without power at the moment). No green light at heated bed while heating.
I can reboot printer, and repeat process.

i use RAMPS 1.4 and Marlin
board type set to 33

If i set 40° it beats between 40° and 45° (no green light on board tough)


On my other similar printer there is no such big delta in tamperature (it reach temperature and beats around 1 degree)

Here is the photos:
Wiring:


Heated bed:


Power supply model


Power supply wiring:

]]> AlexNZ RAMPS Electronics Tue, 14 Jan 2014 00:51:07 -0500 https://reprap.org/forum/read.php?219,289361,294145#msg-294145 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,294145#msg-294145 skangreprap RAMPS Electronics Mon, 13 Jan 2014 16:53:07 -0500 https://reprap.org/forum/read.php?219,289361,292397#msg-292397 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,292397#msg-292397 rcazwillis RAMPS Electronics Fri, 10 Jan 2014 09:16:21 -0500 https://reprap.org/forum/read.php?219,289361,292376#msg-292376 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,292376#msg-292376 lazzymonk RAMPS Electronics Fri, 10 Jan 2014 08:38:57 -0500 https://reprap.org/forum/read.php?219,289361,292364#msg-292364 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,292364#msg-292364 rcazwillis RAMPS Electronics Fri, 10 Jan 2014 08:20:53 -0500 https://reprap.org/forum/read.php?219,289361,291568#msg-291568 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,291568#msg-291568 lazzymonk RAMPS Electronics Wed, 08 Jan 2014 18:43:47 -0500 https://reprap.org/forum/read.php?219,289361,291512#msg-291512 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,291512#msg-291512
On the plus side, the ABS part I printed turned out very nice.]]> rcazwillis RAMPS Electronics Wed, 08 Jan 2014 17:23:46 -0500 https://reprap.org/forum/read.php?219,289361,289650#msg-289650 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,289650#msg-289650 rcazwillis RAMPS Electronics Sun, 05 Jan 2014 11:47:48 -0500 https://reprap.org/forum/read.php?219,289361,289629#msg-289629 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,289629#msg-289629 lazzymonk RAMPS Electronics Sun, 05 Jan 2014 11:08:04 -0500 https://reprap.org/forum/read.php?219,289361,289628#msg-289628 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,289628#msg-289628 rcazwillis RAMPS Electronics Sun, 05 Jan 2014 11:06:25 -0500 https://reprap.org/forum/read.php?219,289361,289456#msg-289456 Re: Heated Bed Issue https://reprap.org/forum/read.php?219,289361,289456#msg-289456 lazzymonk RAMPS Electronics Sun, 05 Jan 2014 04:26:27 -0500 https://reprap.org/forum/read.php?219,289361,289361#msg-289361 Heated Bed Issue https://reprap.org/forum/read.php?219,289361,289361#msg-289361
This is a new printer and the heated bed has never been hooked up. I think the mechanics are hooked up correctly.

Marlin:
#define PIDTEMPBED
#define BED_LIMIT_SWITCHING
#define MAX_BED_POWER 255

I don't know where to go from here. Help please.]]> rcazwillis RAMPS Electronics Sat, 04 Jan 2014 19:52:59 -0500