last updated: June 2002.
|Power-Down mode of the
The keyer software turns the internal oscillator off to save power after a short time of "no activity". This state is called "power down"-mode. It is a special feature of PIC processor used in this circuit. You may find more info about this feature in the source file of the keyer software which is available on the author's homepage. With a PIC 16F84 running at about 2.5 Volts, the power consumption should be 1 microampere (maybe less) as long as the keyer is in "power down"-mode.
To achieve minimum power consumption during power down mode, some care has to be taken:
PORTB has its internal pullup resistors enabled, so there is no need to tie unused pins of port B to ground or VCC. It would increase the standby current if you pull any of these inputs (RB0...RB7) to ground !
PORTA has no internal pullup resistors. As most of the pins of port A are
outputs, you don't have to worry what to do with these pins... just leave
all outputs open if you don't need them (RA2, RA3).
If you still can not get the standby power consumption down to 1uA (at 2.4 Volts DC in), check the voltage of all inputs and outputs with a high-impedance DC voltmeter (10 MOhm or more) when the keyer is in standby mode. Here are the DC voltages measured against ground directly at the PIC pins:
Pin1: 0.00V Pin2: 0.00V
Pin3: 0.00V Pin4: 2.49V Pin5:
The voltage drop on Pin 15 may result from the high internal impedance of this signal (OSC2/CLKOUT).