At 01:50 PM 5/22/96 -0400, you wrote:
>
>Edwin wrote:
>[...]
>>      (2) If I have A/C anyway, is there a inexpensive way (i.e. less than
>>      the cost of a AC/DC adapter) to convert A/C to a DC in the PIC
>>      operating voltage?
>>
>>      -Edwin
>
>You could do it with a resistive voltage divider, diode, and capacitor
>to form a half-wave rectifier which would feed a voltage regulator.  The
>single power resistor you would need (it'd have to be able to handle at
>least 2 or 3 Watts) may be expensive, but it would eliminate the need
>for a transformer.


For safety reasons, you might want to use multiple lower power resistors instead
of a single large one.  That way, failure of one resistor will not result in
a high voltage into the regulator/PIC.  Also, the PIC will NOT be isolated from
the AC line, which can be a hazard as well as a grounding problem.

There are also small DC-Dc converter chips that can handle this with less power
dissipation.  Email me if you are interested in more info.


Good luck and be careful!


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Jonathan King        *  Unitrode Corp.                * king@uicc.com
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