August 2014
I have a small LED flashlight that I mount on my handlebars while riding my bike at night. I've seen some people put a flashing white light on the front of their bikes. Is there a circuit to convert my "regular" flashlight to a "flashing" flashlight?
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When I read the question, I remembered that RadioShack sold a blinking LED but in red (part 276-0036). I bought the LED, and testing the current flow while it was blinking, I discovered that the IC inside reduces the current to less than 0.03 mA (30 µA) when off, and conducts over 40 mA when on. So you can buy the blinking LED and add it in series to your LED flashlight. When you turn the flashlight on, the red LED will blink, and make the main LED blink, too.
You will have to open the bicycle flashlight to wire the blinking LED in series to the white LED. This LED can handle up to 5 volts and up to 80 mA (as printed on the package) with no additional components. If you do a web search on the part number, you can find other bicycle projects using the same blinking red LED to flash an array of nine red LEDs for the rear light.
There are a number of different multi-mode LED flashlight driver modules available, many of which include flashing modes. Check out the selection at dx.com. Make sure to get one that supplies a current appropriate for the LED in your light. They also carry complete lights based around similar modules which might be easier than trying to modify your existing flashlight.
