Polarity for 12v input

Hi,

for rev 1.3 could someone let me know the correct polarity for the screw terminals? I used ground as the closest to the corner, and my LM7805 became extremely hot within 30 seconds or so. I think either the LM7805 is the wrong way around (the metal part is facing the outside of the board) or the screw terminal polarity is reversed?.

Thanks in advanced!

So I have done some basic debugging and it seems to heat up only if I have a Pololu board plugged in. Doesnt matter which one, they all seem to cause the voltage regulator to overheat. Which end should the screw pot be facing? Any ideas whats going on?

While it doesn't seem to be the issue, one of my problems was the Pololu driver boards where around the wrong way. Thanks to the "helpful" rev1.3 example photo posted as SL1.3a_dual_z.jpg on the main page which has them plugged in around the wrong way... Might be worth deleting that image?

Edited 1 time(s). Last edit at 10/23/2011 02:40PM by blob.

Ground on my sang 1.3a is closest to the corner. All mosfets have the back facing out. This is easy to confirm with the continuity probe on a multimeter.

I had a similar experience though, when I was testing and had only my bed heater attached. I was heating the bed to 40C and running the axis through a test print. While checking the temps on the pololus I noticed the mosfet for the non-attached extruder had hit 80C+! With both the bed and extruder attached, temps are now normal.

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Hi, thanks for your tips. So, I had the 12v input around the right way. my pololus were wrong way around, but now they should be ok. My mosfets and pololus are room temp, only my vreg gets super hot when a pololu gets plugged in. Do I need to attach the seperate 12v power for each motor? Can I have just one pololu installed for testing purposes? Does it need a motor attached before the vreg will behave? How hot does your vreg get? I hate to admit it, but im thinking i may need to throw my Sanguinololu and move to a ramps... its very hard to diagnose problems with such a small dense board - its like it either works or it doesnt and the only way to find out is right at the end.

blob Wrote:
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>Do I need to attach the seperate 12v power for each motor? No

>Can I have just one pololu installed for testing purposes? Yes

>Does it need a motor attached before the vreg will behave? No

>How hot does your vreg get? Plugging in one Pololu should not make it any hotter at all. They take very little current from the 5V rail.

>I hate to admit it, but im thinking i may need to throw my Sanguinololu and move to a ramps... its very hard to diagnose problems with such a small dense board its like it either works or it doesnt and the only way to find out is right at the end.

Plugging in the Pololus the wrong way probably destroyed them and now they take too much current.

Edited 1 time(s). Last edit at 10/24/2011 08:01AM by nophead.

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[www.hydraraptor.blogspot.com]

Screw of polous to the right with the USB facing towards you. (for future reference).

Will someone take that picture down? That is why I blew my Pololu's as well.

DarkStar2k

Everybody can edit the wiki, so please go ahead.

Some of the pages have "restricted" access, which means, you have to register there before editing. Registration in the wiki is open to everyone, not even moderated, AFAIK.

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