12VDC to 12VDC require an adapter

TrailMaster · 08-30-2001, 12:10 AM

My project is new and though I'm handy with a screwdriver, knife and electrical tape I don't know much about electricity. Please don't laugh at this stupid question...I would appreciate some help.

I am just starting on my first mp3car project, an HP Omnibook 800 mini-laptop acquired on ebay for $205. Eventually I'm going to mount it in my micro-trunk but for now it lives on the passenger seat to enjoy and test. The AC power adaptor that came with the Omnibook delivers 12V at 3.3 amps.

I went to Radio Shack to get a cigarette lighter adapter that would power the Omnibook directly. They sold me ($59.95) a "Universal Notebook Computer DC Power Adapter" that works like a charm. It runs on 11-16V. You can program the voltage delivery with a selector switch from 9 to 24V DC, it claims a maximum power output of 4 amps. They insisted that this was the only thing they had that would work.

Question 1: Why do I need this thing at all? Why not just run from the cigarette lighter to the DC IN on the laptop? It is 12v to 12v, right?

Question 2: If an adapter/power supply is necessary is $59.95 too much to pay? I have 30 days to return the Radio Shack unit if so. Is there a better/less expensive approach.

Eventually I'm going to mount the lappy in the micro-trunk. There is another 12v cigarette plug back there and a CD changer plug. The car also has two 12v outlets up front. I'm using the mini-laptop as a PDA/on-the-road email checker, etc. so at times it will be convenient/necessary to have it up front.

Thanks in advance for the help on the DC power adapter questions.

Arby · 08-30-2001, 12:16 AM

The car's electrical system can vary between 10 and 14V

that adapter takes that, bumps it up to 16 or 20V, then regulates it down to 12V.

It keeps it at a steady 12V. Hooking it up directly to the car isn't a great idea.

I'm sure there are many other, cheaper ways of doing that.

Aaron Cake · 08-30-2001, 08:38 AM

There may be cheaper ways of doing it, but the current capacity, compactness and reliability of your Rat Shack adapter will be hard to easily beat. I'd stick with the Rat Shack DC-DC.

Do not connect your laptop directly to your car's 12V. That is a very dirty system, and will vary between 8V and 16V. The laptop's power supply is not designed to handle this.