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MG MGF Technical - Regulated supply for 12v devices

Hi all,

Looking for a way to deliver a regulated 12v supply from the F electrics, and it's that word 'regulated' that I'm struggling with. Currently using a power inverter and a regulated mains transformer to achieve the required supply, but that's cumbersome to say the least. I'm presuming there is a more efficient way of doing this, but having trawled the Maplins website I don't appear to be any closer to the solution...

Mike Hankin

The key question what sort of current will you be drawing? If its up to around 5 Amps then a relatively simple circuit using a voltage regulator IC should work, if its more then discreet components or a DC to DC converter would need to be used.
C Tideswell

How many amps will you be drawing from this regulated supply?

What are you running that actually needs a 12v regulated supply?



Branko

Apart from the other replies you might want to check out the TI simple switcher devices. Had good results with these a few years ago.
D Billington

If I had both devices running the total draw is around 1200mA. I'm guessing an in-car adapter for notebooks etc could be modified & wired in, is that likely to be the simplest solution?
Mike Hankin

If your into making your own bits try this
http://www.national.com/pf/LM/LM1084.html#datasheet
You might be able to get a free sample.
Don't know much about car electrics but I have a feeling the 12V is about 14V and very noisy. The Input capacitor (C1 on data sheet) probably wants to be 35V. If someone else suggests higher go with them. The tab wants bolting to a big lump of metal, but will need insulating as its not ground!
If you need this to work with the engine off/ with a 12V at 12V then you'll need a more complicated switching regulator.
JohnB

The MC78xx range that Maplin sell might be what you're looking for (1A max) the xx is 'output voltage' but * the input voltage _must_ be greater than 14.5 volts, the output of your alternator is about 14.5 volts, so it might be a little marginal. How much current do you need?

The MC78xx range has a grounded tab, which means you bolt it securely to the body and forget about having to fit any fins, the contacts then are just, in, bolt and out.


Will

*this is a problem you will get with almost all regulators, for small currents you could use a zenner instead.
Will Munns

LD78xxCV is basicly the same device (also from maplin) but 2A
Will Munns

I can't imagine what you want to run that requires such regulation. These regulators are providing devices with a reference input voltage, where the voltage really is critical.

Depending on what you want to run, It would be more practical just to use some basic suppression: Choke, Diode and a pair of capacitors.

What exactly do you intend to power?

Dave
David Monks

This thread was discussed between 30/12/2005 and 03/01/2006

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