Polarity lesson: $200


Senior Member
Here's hoping I didn't just spend $200 teaching myself about polarity, or more specifically, about what happens when you roll the dice.

My security camera server setup was going ludicrously smoothly. The server build and kodicom card install took all of an hour. That should have been my first clue. I finally unpacked the security camera and universal power adapter got from Tech-home months ago, looked at it, realized the documentation didn't state what the polarity should be on the power adapter. Spent some time googling, couldn't figure it out, so I figured, what-the-heck, i'm not going to figure this out via osmosis, so I may as well try one.

Got it all plugged in, no image on the screen. Hmmm. Wonder what it could be. I jiggled all the wires, no love.

I then looked over at the wallwart, and said to myself "Hey - why isn't that green LED indicating power on anymore?". I took it out of the wall.

Oh my was it hot. Real hot. Really really hot. Not burning hot, but hot. Much hotter than power supplies are supposed to be. Did I mention it was hot?

Hey - reversing polarity may not be a good idea...

Anyhow, Radio Shack is closed now, but I'll swing by tomorrow and pick up another universal power supply.

And hope like heck that I only fried the $25 power supply, and not the $140 security camera.
Check that power supply with that multimeter you have. It should be 12 volts DC I imagine (read the power supply output specs).

Just plug it in the wall, set the meter to DC volts, put one lead in the center of the connector and one on the outside of the connector and this will tell you if that wall wart is still functional.

On wall warts with a connector there is a symbol which looks like a half Circle with a dot in the middle. If the "+" is shown connected to the "dot" that means positive reference will be at the center conductor (reverse if the "-" is shown connected to the "dot").
yeah, that was the first thing i did. Still got that multimeter handy from the Elk stuff yesterday :D [he can be taught about multimeters!]

No love. It's definitely toast.
Not too likely on a wall wart, but. . . did you check it while it was still hot? Sometimes power supplies have a thermal breaker and it might reset when it has had a chance to cool off.

You might want to check, one of my camers is 12 AC not DC. I almost accidently tried it on DC, but for some unknown reason I re read the instructions.

I was building a lcd picture frame for the bedroom (non touchscreen - camera view's and still pictures. I had built a very nice frame had installed and tested everything. It was working great. And THEN, I had one of those stupid double pin universal adaptor from radio shack and plugged in the LCD the wrong way = no more lcd picture frame. A full day of tinkering and it was all gone in 2 seconds. Be careful with polarity. It was only $100.00 lesson but the lcd was discontinued so everything was a waste, no replacements.

I now rip off those STUPID adaptors and test polarity on everything with a multimeter. That product was poorly engineered. It does not make anything easier, just costlier.
DeathtoToasters said:
tech-home said:
It should be center positive & 12volts.

I'm going to install on of these.
Can you give an exampple of how this is used? I am a bit confused?

Cut the actual plug that goes into the wall, strip the +/- wires and hook them into this panel?

All power to one area, then one power plug into the wall?

You've got it... provides a nice clean way to distribute power if you have a number of devices with similar power requirements.

I've got a few of these installed at my house (Altronix brand) They provide power to all the ADI gear, PIR's, Door Locks, etc. and also have battery backup so they run independantly of the rack UPS which runs for a much shorter time without power. There are some small pictures if you scroll down a bit in this link:


IF you are going to use an alternate power supply with some serious amperage capability, I would recommend using a distribution box such as THIS.

This way if one of your wires gets shorted for your glass breaks, motion detectors, cameras, etc... you will not take down the entire supply. Of course if you are only using it for a certain few items, this is not needed.

You also have to consider the power draw of your distributed power to your devices when selecting the current capability of each individual feed.
Well, it looks like that old camera is toast. I got a 2nd one in today [along with a 1.5A PS, and the Elk PD9HC as recommended above].

New one works fine, old one doesn't.

Live a little, learn a little.