Rainy day project ...

[RobertM]

I just wanted to let you know if a little project I did recently.  The idea was to provide regulated 12v and 5v supply voltages for powering astro equipment from a car battery.  Behind this was the fear that one day I might actually have a 'blond moment', connect things up the wrong way around, take out a lot of expensive kit and start crying.

It would also stabilise the voltage and provide a better electrical environment for all the sensitive equipment that we astronomers use.

The Spec. was:

1) Reverse polarity protection in case of incorrect battery connection
2) Stabilised regulated 12v up to 8 amps
3) Stabilised regulated 5v up to 3 amps for USB hubs
4) Clean glitch free control of power on/off
5) Multiple 12v cigar sockets that were waterproof and locking (so equipment doesn't get disconnected accidentally.
6) work off battery voltages between the range 9-15v
6) The electronics must have a low power footprint.

What I ended up with was all of the above is a box about 8" x 6" x 4".  On one side are three locking marine 12v cigarette lighter sockets, on the other a power switch (which disconnects the unit from the battery) and a power up push button (tells the PSU to power up).  On the bottom there are 2 x 2.1mm jack sockets for 5v power and 4' power cable with the battery connectors.

The PSU is a stock Car ATX PSU from LinITX in a plastic maplin box.  The PSU is very efficient, gives off virtually no heat so works well inside a sealed plastic box.  The PSU is rated at 120W and takes an input voltage of between 6 and 32v making it very versatile, also all the output curcuits are short curcuit protected.

It was very easy to construct - the most tricky part was drilling holes for the 12v sockets ! Cost approx £60 - yes, expensive but compared to making a mistake I thought it was worth it !!

If anyone wants more details then let me know.

Robert

[Carole]

Have you got a picture of it?

[MarkS]

That's a great idea Robert.  I wouldn't mind seeing a piccy of it completed.

One question - what *does* happen if you connect it up reverse polarity?

Mark

[RobertM]

One question - what *does* happen if you connect it up reverse polarity?

Nothing i.e. you dont get any power.

Will take some pics tomorrow...

[RobertM]

Have posted pictures and description on Flickr http://www.flickr.com/photos/29673723@N04/