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'troubled sleep: '84 seems restless'
1999\04\29@092728 by robert a. moeser

picon face
hi!

i have a simple 16F84 circuit. you will see it in your mind fully as a
matrix of 16 LEDs scanned in a 4x4 matrix and 16 switches also scanned
in a 4x4 matrix.

i use 4 output lines to sink current from a row of LEDs, 4 output lines
to source current to one column at a time and 4 input lines to sense the
switches.

i diode-isolated the switches also.

the PIC runs at 4 MHz on a resonator and power is supplied by a 6 volt
battery. i have a 10 uF tant and a 0.1 capacitor in parallel with the
power supply near the PIC.

i use a one transistor "brown out" reset switch i saw in the Microchip
book. it solved an old problem.

on the breadboard, using a 2x2 matrix of LEDs and a 2x2 matrix of
switches (first two rows and columns) the circuit and my program perform
to design, and when the time comes, it goes to sleep nicely and draws
around 10 uA, about 5 wasted in the brown out circuit\ and 5 for the
PIC.

great!

but... once i build the stupid thing with the full matrix and (i do not
know what else i must have done) the things sleeps on schedule but draws
a whopping 60 uA.

so i need suggestions for tracking down things that can comprimise what
i thought would be a straight-forward low power design.

-- rob

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