Here is a schematic of a possible protection circuit.
Now do you see where the 1V drop comes from? If the
I/O pin on the processor is at 5V and 15mA flows
through the series resistor, What is the voltage on
the other side of the resistor?
--- In Electronics_101@yahoogroups.com
, "Kelvin Lau
<kelau@h...>" <kelau@h...> wrote:
> I'm using a Microchip PIC16F874. Which can source
25mA per I/O, but
> have a max. of 200mA sourcing capacity for the whole
chip. I don't
> quite understand your explanation regarding the max.
resistance I can
> have is 68ohm. what's the 1V drop coming from?
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