In my city, as I guess in many other, you'll always have to do your best to stay alive when you ride your bike, this is particularly true by night. This is the reason which brought me to design this circuit.
I anticipate worried drivers (I should be the first to complain) saying that my bike light hadn't become a stroboscopic floodlight which makes you blind, only catch your attention a little more than before, it will be more as looking at an old very used neon light.
Step 1: the frequency
This blinker circuit runs at about 50 Hz, this means that it's very near to the frequency at which our eyes work. So you'll see an "almost" fixed light, the difference with a fixed light is that it's a little bothersome to see, and it keeps your attention at once. Indeed old TVs and PC monitors worked a few hertz more than this frequency, and after some hours in front of those, your eyes were tired. To work long periods in front of your monitor it's better this is 60 Hz or more (more or equal to 85 Hz with old crt monitors, LCD are less stressful).
This circuit is intended to work with any LED light with a power source of about 4.5-6V. If you have different voltage you have to review the design adding a voltage regulator (or booster) for the chip.