dnb

I was looking for a more elegant solution for a similar problem. I bought an integrated circuit switching regulator from RS to power a laptop in a yacht not so long ago. It delivered 4 amps and several could be used in parallel.

Think it was an STL296...

Thought at the time it could be useful for an in car MP3/gps/etc... (Dont get me started on that one!) computer.

Edited as I forgot to say the output voltage is variable - set by a potential divider.



[Edited by dnb - 5/4/2002 10:30:50 PM]

alistair

Is there a device that I can plug into the cig lighter (or wire to battery) that will provide a smoothed and regulated output ?

I want to use a portable DVD in the car.

The only other option I have is a 12V to 240V invertor then plug the mains lead & transformer into that which seems like an inefficient process.

globbits

Hi Alstair/HKSubaru

You can get a regulated power supply quite easily - the likes of Maplin/RS will sell you a 5V or 12V voltage regulator and all you need is a couple of smoothing capacitors for the input and output wires. If you need less than 12V, a diode drops approximately 0.7V per diode, so just connect enough up in series that you've got the voltage you need.

Current-rating is going to be your big issue, rather than feasability. If you're driving a DVD player and screen, that's a fair wadge of current. Although a suitable voltage reg. for high (a few amps) current isn't a problem, suitable diodes aren't going to be cheap.

Considering the price of a 12V-240V inverter, if you bid on EBay (I got one for £45 including postage) you might consider this option, since it's a bit more presentable than a 1"-square bit of veroboard!

chiark

Maplins are selling 150W invertors for 19.99!

OK, it's inefficient, but it's cheap

alistair

Thanks guys - I've already got an invertor and was sort of hoping for a more elegant solution - but I guess not.

alistair

Thanks - it looks like RS are the boys.

Stock code 361-4804

High quality regulated d.c. to d.c. converters
Converts power from a 12V car battery
Switch selectable output voltage:
Model UNI 12/MA 3/6/9/12V d.c.
Model UNI 15/M 1·5/3/4·5/6/7·5/9/12V d.c.
0·4 metre (approx) input lead fitted with cigar lighter input plug
1·7 metre (approx) output lead with polarity inverter and set of 6 output connectors
Short circuit and overload protection
LED power indicator

£12.33

chiark

Superb - one to keep in the favourites then

globbits

Just found the same thing at Edworthys - or sumfin like it....
http://www.edworthys.co.uk/acatalog/Edworthy_s_Catalogue_Voltage_Converters_254.html

alistair

That looks like a neater solution as it can be hard wired.

Clickable link to edworthys