ady8077
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| posted on 20/3/06 at 06:01 PM |
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15v out of 12v
Hi all
Any electronic experts about?
Is it posible to make a 15v regulated supply off a cars battery?
I was thinking of using something like a L78S15CV volt reg I C but i'm not sure if you have to have more than 12 volts input
Adrian
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nick205
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| posted on 20/3/06 at 06:25 PM |
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you can do this quite easily using DC-DC converters. Usually the output current at the higher voltage is limted, but with car electrics where
"amp"le  current is available this isn't a problem.
A quick google on car inverters will show loads of products that can be connected to a car battery and supply 240V for connecting appliances in
caravans etc.
HTH
Nick
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EViS
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| posted on 20/3/06 at 07:11 PM |
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Are there any problems with installing such an inverter into a car (passenger side, down by the footwell?) prior to SVA? Would like one of these in
order to connect the laptop/PDA up with ease, would also try 'integrating' the box into the interior so that only the 3-pin plug socket
shows...
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MkIndy7
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| posted on 20/3/06 at 07:24 PM |
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You can buy adapters that plug in to a cigarett lighter socket that do 12V to whatever the laptop/pda needs from places like Maplins, there only about
£15 when on offer.
http://www.maplin.co.uk/Module.aspx?ModuleNo=36836&criteria=Notebook%20Adaptors&doy=20m3
Better than having the 3 pin (presumably 240V) socket on show (EVis suggestion) and an inverter is usually more expencive the above adapter.
SVA wise I wouldn't put it on untill after or they'd probably want it to obe an exterior quality fitting.
For whatever "ady8077" use was, have you tried running it off 12V first? it might work off that as it rises as hight as 13.5 when the
engines running.
[Edited on 20/3/06 by MkIndy7]
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DanP
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| posted on 20/3/06 at 07:53 PM |
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for a voltage regulator you'll need more than a 12 volt input - they are designed to make a lower voltage out of a higher one.
to pump up the voltage you will need a DC-DC converter - RS or farnell have a large range- usually no more than £5-10 like
HERE
just make sure you choose one which will meet you current requirements where the power rating (in Watts) should be more than the number of amp's
you need times 15 (P=VI)
HTH
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ady8077
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| posted on 20/3/06 at 09:01 PM |
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Hi
Its for an old laptop i got off ebay, it didn't come with any psu
I didn't no about dc to dc converters, i'll have a search
the laptop needs 15v 2amps
Adrian
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paulf
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| posted on 20/3/06 at 10:51 PM |
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Maplins have them , about £20. I also need one for the same purpose and did find a design for one but havent access to it at present as its on a spare
harddrive not fitted to my Pc at present , to be honest for £20 its not worth building one though.My laptop is 14v battery and I have found it wiill
run on 12v but is prone to crashing at any slight voltage drop below that , in a car with the engine running it may be ok.
Paul.
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MikeRJ
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| posted on 20/3/06 at 11:13 PM |
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Paul's right, for £20 it's not worth the cost of building a switched mode DC-DC converter. They often need custom made magnetics (i.e.
inductors and transformers) and generaly require a well designed PCB for reliable and stable operation due to the high frequency, high current
switching.
A "bodge" way of doing this is to get the 150Watt mains inverter which Maplin sell cheaply (or used to, though it's doubtless
available on Ebay) and then use a standard main charger.
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ady8077
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| posted on 21/3/06 at 06:05 PM |
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Hi
I didn't realise maplins would be so cheap, your right for £20 its not worth making anything
As for a cheap inverter, that wouldn't help as i havn't got a mains charger
Thanks
Adrian
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