I have two 08M PICAXE chips running from a single 9V supply through a 78L05 regulator. This regulator should supply a constant 5V supply as long as input voltage remains above 7V. Both PICs are running at 8mhz.
There is a 10uF and 220nF capacitor across the 9V supply and a 100nF and 10uF capacitor across the regulated 5V supply.
When a good 9V battery is attached and the circuit is switched on (terminal voltage drops to ~8.2V), or when a 9V power supply is used, the circuit behaves very erratically. It is controlling an Ultrasound Range Finder, and the system returns random values. Sometimes the PICs will "crash" and the status LEDs attached to their output 0's flicker on and off, or just turn off completely and the PIC stops responding.
However, when a bad 9V battery is used and the circuit is turned on (terminal voltage at ~7V, regulated voltage ~5V), or when the power supply is used at just 6V (regulated supply ~4.5V), the system works fine and returns correct values.
Any ideas what's going on here?
TIA,
Jon
There is a 10uF and 220nF capacitor across the 9V supply and a 100nF and 10uF capacitor across the regulated 5V supply.
When a good 9V battery is attached and the circuit is switched on (terminal voltage drops to ~8.2V), or when a 9V power supply is used, the circuit behaves very erratically. It is controlling an Ultrasound Range Finder, and the system returns random values. Sometimes the PICs will "crash" and the status LEDs attached to their output 0's flicker on and off, or just turn off completely and the PIC stops responding.
However, when a bad 9V battery is used and the circuit is turned on (terminal voltage at ~7V, regulated voltage ~5V), or when the power supply is used at just 6V (regulated supply ~4.5V), the system works fine and returns correct values.
Any ideas what's going on here?
TIA,
Jon