security rear light

7-38 elektor july/august 1980 Living in a temperate climate involves having to cycle with lights on every now and again. The trouble is that a bicycle dynamo can only produce energy for lighting while a steady rate of pedalling is kept up. As soon as you slow down before traffic lights, zebra crossings etc. the intensity of the rear light drops considerably, thus making it very difficult for vehicles coming up behind to see you. The safety rear light described here is an indispens- able addition to the normal reflector. As soon as the dynamo is switched on and producing a voltage, the rear light will come on. The light will have a constant intensity no matter what cycling speed is kept up. Furthermore, it will continue to burn for about four minutes after the bicycle comes to rest, which is ample time to cross the busiest of cross- roads. Unfortunately, this circuit has a drawback — it relies on batteries and when these are dead the system will not work. One consolation is, how-...