build a blinking safety light for your bicycle

Posted on Feb 6, 2014

The circuit I used is a very common one. You can do a google search for 555 timer LED blinker  and find hundreds of schematis that will fit the bill. Here is the schematic for my particular flavor of LED blinker: The variable resistor (100K) in the schematic above may not be included in other designs with a fixed blink rate, I included it here so that the blink rate

build a blinking safety light for your bicycle
Click here to download the full size of the above Circuit.

can be user adjustable from about 1hz to several hundred hertz. I didn`t include mounting hardware in the parts list because you will need to do some thought on your own to decide how your enclosure will attach to your particular bicycle. My bike has a small metal piece above the rear tire with holes in it, so it was only logical to attach my enclosure here with a nut and bolt. Wire this circuit up on your perfboard and insert it into your enclosure. Mount it on your bike and you`ll hopefully have something like this! Make sure you wire your LED`s in parallel! I had been testing the circuit on my breadboard with a 9v DC wall adapter as the power supply, this is slightly different from using a battery, as it will deliver ~14v to a lightly-loaded circuit. I had wired my LED`s in series, and with the wall adapter everything worked fine. However, when powered by a 9 volt, the four LED`s I had wired in series dropped more voltage than the 9 volt could deliver, so the circuit failed to operate. The easy fix for this is of course to wire the LED`s in parallel, so that collectively they can only drop the same voltage as a single LED would (which is ~1. 5 volts). You can see how everything is laid out in the enclosure in the photo above. I soldered the circuit to the perfboard before cutting the excess off with a Dremel. The screw holes on the board don`t line up with the holes in the enclosure perfectly, so I only used one corner...

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