i'm wanting to run an old laptop in the car and seeing as I've already had a few accidents with other car wiring experiments I thought I'd ask for some advice before blowing up the laptop. basicaly all i want to do is run my laptop off 12V @ about 1.2A I have an lm317 or something lying around here and i thought about using a transistor to increase the current handling of the regulator. 3 q's I guess.. will there be enough volts to run a regulator and the laptop? (only really need it when the engine's running so there's probably 14V or more available?) any tips for using transistors to increase the current capabilities? (think there are circuits in the data sheet but any advice would be great, even just a 'yeah it works fine') is the cigarette lighter likely to be run off the battery? yes I know maplin sell laptop regulators but I don't feel this is worth spending much on. cheers
For starters you'd be better with a low-dropout regulator. A 317T needs around 14v input to give 12v, so your lappie may crash when you blow the horn.
the laptop regulator is a invauable source if you own a laptop, not only will it not go out when you "blow your horn" but itl put out a very regulated source of power. There not that much if you think about how much your laptop is worth and what could happen to it with bad circitry. -Wndrbread
Well in that case If you can change the 12v to 14v or more, you can use a lm317 then. Car amps have to change 12v into a higher voltage, (I think its the mosfets that can amplify the voltace) and if you can get it to 15v then the LM 317 would work fine. Though I'm not sure how you would raise the voltage. any thoughts cpemma?
I got mine for 64 ac mobile power Although it may to much i just couldnt help linking it : P but anyway, i hink its possible to up the voltage i just cant remeber how. (takeing business classes, everything else is on the side burner ) ask cpemma or zapwizard. Wndrbread
12v 1.2A seems a bit low, but if that's genuine a LDO reg like the Micrel MIC29152 I used here will handle 1.5A and only lose a fraction of a volt overhead. It's adjustable, so you could tweak it to the minimum voltage the lappie will run on, maybe 11.75v. And a load of smoothing (1F cap?) on the input side would help when demand goes high. Maxim do a load of voltage-booster chips, but you're getting complex for somebody who wants cheap.
ahhh pop in to halford and get a invertor its 12v -240v plugs in t *** lighter then plug in the 3 pin plug its not the smallest unit , i wired one in hard wire to customers car tyesterday so he can power his xbox it works fine just dont mix the palarity up. they use to be like £100 but halfords had one in farnham surrey yesterday for £40.
