Audio-Verstärker (100 W)

Circuits for bicycle speedometers have been fairly common (Elektor published one in last year`s Summer Circuits issue No. 39/40), the differ-ence in this particular design being the digital readout. The speed sensing is carried out by a number of magnets attached to the spokes or rim of the wheel which operate a pair of reed switches. The principle is illustrated in the drawing in figure 1. where the reed switches are shown fitted on the b icycle front forks.