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subego · Dec 19, 2012, 01:27 PM

I'm converting something which runs off of low voltage DC provided by an AC transformer into a DC only version.

I can't think of any reason not to yank the AC ground wholesale, and even if I had a reason I'd have no idea what to connect it to.

Am I missing something?

P · Dec 20, 2012, 12:29 AM

Impossible to say without knowing more about the setup. What are you installing, and where are you installing it?

The Final Dakar · Dec 20, 2012, 06:17 AM

osiris · Dec 20, 2012, 06:51 AM

Nice ass.

subego · Dec 20, 2012, 08:19 AM

Originally Posted by P

Impossible to say without knowing more about the setup. What are you installing, and where are you installing it?

How much detail do you need?

It's an LED pin spot, like you'd use on a disco ball. Actually, it's exactly that.

So, 3W LED mounted to a metal plate. The plate is what is grounded in the AC version. It's exposed metal.

My modification runs it off of 8 AA cells. Not something I'd like to short with my tongue, but seems as safe as you can get otherwise.

subego · Dec 20, 2012, 08:20 AM

Here's a pic if it helps:

subego · Dec 20, 2012, 08:49 AM

Small detail: the LED runs at 3.3v. I have a DC-DC transformer regulating the voltage from the AAs.

reader50 · Dec 20, 2012, 12:57 PM

The ground is a shorting return path for stray current. ie - if a live wire shorted to chassis, the maximum current will flow in order to trip the breaker or fuse. With DC-only power, it doesn't serve much purpose. You could go the auto route, tie it to battery negative as a chassis ground.

Maybe whatever it's mounted to would be a useful sink for static electricity. Passerby scuffs feet, shocks lamp, voltage regulator dies. This seems unlikely though.

subego · Dec 20, 2012, 01:11 PM

If it isn't attached to a good static sink, wouldn't grounding exposed metal to the battery make it more likely to shoot static into the regulator?

subego · Dec 20, 2012, 01:11 PM

God DAMMIT, Huddler.

reader50 · Dec 20, 2012, 09:11 PM

A good question is worth asking twice. A great question would be worth 3-5 copies.

I can't think of a reason why you should tie it in. For a small battery system, there's no obvious advantage. You could loop the ground, connect it back to it's own terminal. That way it will protect itself.

subego · Dec 20, 2012, 09:13 PM

Also, while I'm here, what would be the best practice for strain relief on the wiring for the voltage regulator?

It's a tiny little thing. Like two nickels.

subego · Dec 20, 2012, 09:17 PM

Originally Posted by reader50

A good question is worth asking twice. A great question would be worth 3-5 copies.
I can't think of a reason why you should tie it in. For a small battery system, there's no obvious advantage. You could loop the ground, connect it back to it's own terminal. That way it will protect itself.

Protect itself? My brain can't wrap around this one.

Isn't a piece of metal, and a piece of metal with a single wire looped back to the same terminal, in essence the same thing from an electricity standpoint?

reader50 · Dec 20, 2012, 09:43 PM

Yep. But instead of a dangling wire, you'd have a handy carrying loop.

ghporter · Dec 24, 2012, 03:09 AM

Keep the ground wire and connect it to the regulator's mounting hole (the circular hole just to the right of the white clip in the picture). That will do the "protect" thing for the regulator and assist in maintaining the regulator's own ground reference involved in its regulation. Thus, if something BAD happens (even with the 8 AA batteries), the regulator could shut itself down instead of burning up a component.

subego · Dec 24, 2012, 11:27 AM

Cool!

I was wondering what that was for. Thanks!