> me being unable to measure current wouldn't it be easer and safer
> (for me) to put a $0.53  voltage regulator that can handle up to 35
> volts and outputs 5 volts and a 150 ma current between my pic
> and power supply ?

You've a couple of options -

The PIC will work perfectly well with 3 nominally 1.5V cells. You
didn't say whether these are rechargeables or not, but either way it
would be OK. For example 3 fresh NiCd might be 4.2V total, 3
fresh alkalines might be almost 5V total. The PIC should run all the
way down to 2V so 3 cells should last a while, below 'flat'

or

Use more cells to get above the threshold for a 5V regulator. One
like the 7805 needs around 8V on its input to maintain 5V output

LDO (low drop-out, ie the difference between input and output)
types have a lower threshold, so even as low as 5.1V on the input
will give a 5V regulated output

Option 2b is making your own regulator. This can be done quite
simply with an LM317 and a couple of resistors. They're usually
about the same retail price as a 78L05

http://www.national.com/ds/LM/LM117.pdf

For on-going use you would be better to have a mains-derived 5V
supply. Find a transformer / wallwart / plugpack that puts out DC
in the 8 - 12V range, and regulate it down to 5V. Include a bridge
rectifier and smoothing capacitor
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