Monday, October 24, 2011

Improved Traffic Light Bike Light

This projects was done a while ago (1/6/2010) but it's never too late to post!

The first iteration of this project worked quite well. However, it wasn't very compact because the blinking was done by an external Arduino board which was overkill, messy, and needed a separate power supply. So for the second iteration of this project, I decided to make the control circuitry contained entirely within the UPS.

Step 1: Make a blinker circuit. It turns out this is really easy to do with a simple 555 timer IC and some help online. I picked my resistors and capacitors to give this a duty cycle similar to other bike lights I owned. This is a picture of the circuit on a breadboard before I soldered it up to protoboard that shows how simple it is.

Step 2: Find power in the UPS. It didn't make any sense to power this thing externally when I was dealing with uninterruptible power supply with plenty of control circuity. The 555 timer I bought works with anywhere between 4.5V and 16V. So I turned the thing on and carefully probed measured various places on the board until I found one that was giving me 12 volts. After that, getting the electronics working was as simple as soldering it all together.

Step 3: Put it back together. Finally I was ready to make it look pretty. I taped up wires, put the 555 circuit in some extra space, and added a couple a couple doses of hot glue. Afterwards you wouldn't suspect that I had been in there are all. Success!

I did actually use this on a few rides to and from work and it worked splendidly if a bit heavy because of the lead acid battery. Especially at night, the traffic light is amazingly bright. A great next step would be ripping out all of the AC circuity and getting this working with some lighter batteries DC only.

Technologies: A/C Electronics, Basic Electronics, soldering iron


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