rowspan=2 width=10 nowrap> « back to results for ""
Below is a cache of http://www.discovercircuits.com/Andy/Safetyflasher.pdf. It's a snapshot of the page taken as our search engine crawled the Web.
The web site itself may have changed. You can check the current page or check for previous versions at the Internet Archive. Yahoo! is not affiliated with the authors of this page or responsible for its content.
Safety Flasher Category: Projects

Safety Flasher

This circuit alternately flashes two high-brightness LEDs as a safety measure during
jogging or walking. The LEDs 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 battery voltage.


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.