At 14:14 1/06/99 -0700, you wrote:
>Like you I am always baffled with the number of applications
>
>William Chops Westfield wrote:
>>
>> The original request was for a pic project running off a couple of N cells.
>> (at 3 volts?)  A diode was mentioned (in the original message) as being
>> unacceptable because of the high voltage drop (.7V) A bridge rectifier has
>> two diodes in the circuit for a 1.4V nominal voltage drop (you might as
well
>> discard one battery!)
>
>Like I said, I was late to the conversation and the one I commented on
>mentioned something about 4 'AA', or 6 volts. That could handle a couple
>of diode drops. Particularily if a low forward voltage diode could be
>used. I can see if the application was only 3V this would be
>unacceptable.
>
>> In micropower circuits, even when you can afford the voltage drop, you
might
>> end up dissipating nearly as much power in the diode as in the micro (well,
>> probably not, but it's still an annoying place to lose ANY power.)
>
>I somewhat agree. No power dissipation in a protective circuit would be
>ideal, but compared to some of the other suggestions (like none, or R's)
>I think the diode dissipation would be OK. Course, in light of the 3V
>requirement, all that is a moot point.
>
>>
>> I fully agree that a bridge rectifier is an excellant solution in any
>> application where there is sufficient excess voltage and current
consumption
>> is not a major issue.  I'm shocked, for instance, at the number of 9V and
>> 12V (automotive) applications that don't include such obvious protection.
>
>Couldn't agree more. This has also baffled me.


If you use a bridge rectifier then the device ground is above that of the
vechial

Dennis