Jai Dhar wrote...

>1. What is the best way to cut metal for creating jacks such as mains
>receptacle jack (the exact same 3-pronged jack you can find on your computer
>power supply). It's a funny shape - so what tools would I need to cut this? A
>friend of mine suggested a dremel, but I'm not sure how accurate this would
>be. I also need holes cut for a 16x2 LCD, and other misc stuff.

I use a nibbler, followed by file and sandpaper to smooth the
finished cutout.  It's slow, and takes a bit of care to get
good-looking results, but it works.

>2. Short-circuit protection - is there a relatively simple method I can use
>for protecting my power supply from being short circuited?? I have reversed
>GND and Vcc in the past before, so I thought this might be a good idea to
>implement.

I include current limiting in my supplies, as in the adjustable
outputs of this general-purpose 3-output supply:

http://mywebpages.comcast.net/dilatush/labsupp.html

In this example, the outputs are limited to around 60 mA.

For +5.0 volt regulators, I usually use National's LP2951CN
regulator.  It current limits at about 150 mA and includes
overtemperature protection.  I've used hundreds of them, and
haven't blown one up yet.

If you use current limiting, you don't have to worry about
blowing things up.

>3. One of my regulators is a linear type (the +12v), and boy does it tend to
>heat up fast! First of all, how can I minimize this heat. Of course, a
>heatsink is probably the first method of protection - which I have already
>used. I have simply bolted the heatsink onto the case (it's a to-220), but
>should I be using some kind of compound between them? Sort of like the stuff
>you might find between your CPU and the heatsink. Are there more efficient
>ways of cooling the regulator (leaving aside liquid cooling of course). I have
>also used a +12V fan, and the darn thing sucks up 200mA as it is, so with that
>as my only load, the regulator is already heating up! Mind you, it doesn't
>heat up to the point where I think it would be damaging (with the heatsink
>bolted on), but if the fan itself is causing some heat.. how much more can it
>take? (ironic how a method of cooling ends up generating more heat).

The best thing to do is feed your regulator chip all the voltage
it absolutely needs to keep the output in regulation, and no
more.  Any excess input voltage will only make the regulator
hotter.

HTH...

Dave D.

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