Hello, I thought I'd try my hand at putting together this board and I've got Sprinter loaded onto it and, as a quick test before installing it, it's sending instructions to the motors and I'm quite pleased. For the test, I've hooked it up to a bench power supply at 12V and capped it at 250mA. Without the USB cable attached, it pulls a mere 40mA. When I plug the USB cable in, it hits 160mA power draw, just sittin' pretty. What concerns me, though, is that the 7805 gets quite hot to the touch. I can't hold my finger to it longer than 5 seconds, and I've measured 67C on its backside. According to the datasheet, operating temperature is 0C to 125C, and it has built-in thermal protection, but I wonder if it's really normal. I don't have anything hooked up to it (detached the motor when I noticed it got hot) other than Stepstick drivers plugged in, so I'm just looking for a sanity check. Thanks! https://reprap.org/forum/read.php?158,109719,109719#msg-109719 Sat, 06 Jun 2026 01:10:50 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?158,109719,131637#msg-131637 https://reprap.org/forum/read.php?158,109719,131637#msg-131637 ElMatador Sanguino(lolu) Sun, 06 May 2012 16:46:14 -0400 https://reprap.org/forum/read.php?158,109719,131478#msg-131478 https://reprap.org/forum/read.php?158,109719,131478#msg-131478 Traumflug Sanguino(lolu) Sat, 05 May 2012 07:35:14 -0400 https://reprap.org/forum/read.php?158,109719,131447#msg-131447 https://reprap.org/forum/read.php?158,109719,131447#msg-131447 nophead Sanguino(lolu) Sat, 05 May 2012 03:58:19 -0400 https://reprap.org/forum/read.php?158,109719,131423#msg-131423 https://reprap.org/forum/read.php?158,109719,131423#msg-131423 ElMatador Sanguino(lolu) Fri, 04 May 2012 19:55:53 -0400 https://reprap.org/forum/read.php?158,109719,131371#msg-131371 https://reprap.org/forum/read.php?158,109719,131371#msg-131371
The problem with Sanguinololu is that both the USB VBUS and the regulator connect to the 5V rail. That is very bad for the regulator and the PC. The regulator will give a much more accurate 5V signal than the USB. The only downside of this mod is you can't talk to the board without the 12V PSU being on, but since it doesn't control the PSU there would be no point.]]> nophead Sanguino(lolu) Fri, 04 May 2012 14:31:15 -0400 https://reprap.org/forum/read.php?158,109719,131359#msg-131359 https://reprap.org/forum/read.php?158,109719,131359#msg-131359 ElMatador Sanguino(lolu) Fri, 04 May 2012 13:09:21 -0400 https://reprap.org/forum/read.php?158,109719,123978#msg-123978 https://reprap.org/forum/read.php?158,109719,123978#msg-123978
Thanks for your help!]]> sloth Sanguino(lolu) Tue, 13 Mar 2012 15:17:59 -0400 https://reprap.org/forum/read.php?158,109719,123860#msg-123860 https://reprap.org/forum/read.php?158,109719,123860#msg-123860 sloth Sanguino(lolu) Tue, 13 Mar 2012 02:00:16 -0400 https://reprap.org/forum/read.php?158,109719,123850#msg-123850 https://reprap.org/forum/read.php?158,109719,123850#msg-123850 -------------------------------------------------------
> This sounds a lot like my problem. The 7805 also
> gets very hot (I actually burned my finger when I
> touched it) and in addition the printer resets
> itself during prints > 30 min and freezes then. I
> cannot measure the current right now, so I am not
> 100 percent sure if I have the same problem. I
> will check that tomorrow.
>
> How do I "cut off one of both 5V supplies" then?

Honestly, the best solution is to get a USB hub that hits +5V better than your current setup. Cutting 5V supplies reduces the flexibility of it, IMO, in ways I'll describe below. One word of caution is that I'm just glancing at the 1.3a board, I haven't really rigorously studied it, or attempted any of these myself, so consider this a starting point and not a definitive source. :)o

As far as doing it, there are two ways. The least dramatic change would be to just desolder the LM7805. The side effect of this is that the board will NOT work unless it's attached to a computer with USB, since there will be no way to power the logic from 12V. You can also cut the trace in the attached picture named sanguino_no5_01.png (found on the bottom of the board), but if it's not doing anything, you might as well remove it instead of wasting the power on it.

Another location to cut, which would allow you to use it while the cable is disconnected, is shown in sanguino_no5_02.png. The downside is now you can't program/communicate with the board unless it's getting +12V, since the logic is no longer powered from the host machine. Also, another downside is that +5V on the data lines might not match +5V powering the ATMega. The electrical maximum for input high voltage is VCC+0.5, so if your computer's provided logic high is above +5.5V you're going to potentially kill it. Half a volt is a pretty big deviation, though, and I would find it odd if the computer's +5V was that much higher than your Sanguinololu's +5V.]]> Mazaw Sanguino(lolu) Mon, 12 Mar 2012 22:15:43 -0400 https://reprap.org/forum/read.php?158,109719,123783#msg-123783 https://reprap.org/forum/read.php?158,109719,123783#msg-123783
How do I "cut off one of both 5V supplies" then?]]> sloth Sanguino(lolu) Mon, 12 Mar 2012 15:13:55 -0400 https://reprap.org/forum/read.php?158,109719,109889#msg-109889 https://reprap.org/forum/read.php?158,109719,109889#msg-109889 Mazaw Sanguino(lolu) Tue, 13 Dec 2011 10:02:34 -0500 https://reprap.org/forum/read.php?158,109719,109820#msg-109820 https://reprap.org/forum/read.php?158,109719,109820#msg-109820 Traumflug Sanguino(lolu) Mon, 12 Dec 2011 21:02:41 -0500 https://reprap.org/forum/read.php?158,109719,109758#msg-109758 https://reprap.org/forum/read.php?158,109719,109758#msg-109758
I actually hadn't measured the +5V from this particular USB hub before and it's pretty disappointing (4.6V). Dollar store special strikes again, it would seem.]]> Mazaw Sanguino(lolu) Mon, 12 Dec 2011 11:02:19 -0500 https://reprap.org/forum/read.php?158,109719,109729#msg-109729 https://reprap.org/forum/read.php?158,109719,109729#msg-109729 Traumflug Sanguino(lolu) Mon, 12 Dec 2011 04:08:09 -0500 https://reprap.org/forum/read.php?158,109719,109719#msg-109719 https://reprap.org/forum/read.php?158,109719,109719#msg-109719
For the test, I've hooked it up to a bench power supply at 12V and capped it at 250mA. Without the USB cable attached, it pulls a mere 40mA. When I plug the USB cable in, it hits 160mA power draw, just sittin' pretty.

What concerns me, though, is that the 7805 gets quite hot to the touch. I can't hold my finger to it longer than 5 seconds, and I've measured 67C on its backside.

According to the datasheet, operating temperature is 0C to 125C, and it has built-in thermal protection, but I wonder if it's really normal. I don't have anything hooked up to it (detached the motor when I noticed it got hot) other than Stepstick drivers plugged in, so I'm just looking for a sanity check. Thanks!]]> Mazaw Sanguino(lolu) Sun, 11 Dec 2011 21:40:19 -0500