Date: Sat, 18 Jan 2003 15:53:55 -0700
From: Jim Drew
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Subject: Re: PIC controlled variable power supply
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Spehro Pefhany wrote:
>>Ok, but 5ma is way to much current draw for idle times.
> What do you mean by "too much"? Is this battery powered? Then you
> probably should use a different method.
Yes, this is powered by a 9v battery. What I need to accompish is to
activate a medical solenoid for a period (variable) between 4ms and
20ms, and I need to be able to adjust the coil output voltage from 5v to
about 8v to accomodate different solenoids, by just programming the
PIC's EEPROM on the fly. Once the voltage is set, it won't really
change, and any type of manual switch is out of the question. The coil
draws nearly 1 amp of current the first 2ms, and then has a hold current
of about 470ma there after. During the idle time (when the solenoid is
not being used), the circuit must have a low power mode, where the
entire piece of hardware draws no more than 5ma, which is easy enough to
accomplish unless something has to be sitting drawing power as you have