This circuit alternately flashes two
high-brightness LEDs as a safety measure during jogging or walking. The LEDís can be
mounted on clothing or a belt. The circuit draws a precisely controlled 10mA in order to
conserve battery life. Also, the battery voltage can drop to the LED voltage plus about .5
volts before there is a noticeable change in performance.
The LEDs actually act like voltage
regulators. Because the blue LED has a higher drop voltage, it will dim rapidly and then
go out first (about 3 volts) with decreasing battery voltage. The yellow LED will keep
blinking unaffected to about 2 volts of battery voltage. Also due to the higher voltage
drop of the blue LED, the blue LED is on for less time than the yellow LED at normal
The circuit is built into a Radio Shack
4 AA cell battery holder with switch (RS P/N 270-409). The battery compartment farthest
from the switch was used for the electronics. C2 and C3 were added because the long wires
I used for the LEDs caused instability of the flasher circuit. I admittedly went overboard
with the LED wires.