Conventional Bicycle bell has a number of disadvantages: uncomfortable, rattles while riding even on a flat road makes a sharp, unpleasant sound.
These shortcomings are free electronic bell. In addition, it can easily to change the volume and tone of sound. The device operates as follows. When circuit S1 button (Fig. 1) asymmetrical multivibrator transistors V1, V2 starts to generate oscillations of sound frequency. They arrive at single-stage amplifier V3, V4, assembled on a composite transistor. At the same time from G1 battery is charging the capacitor C2, which, after releasing the button continues to nourish the electronic bell. The tone of his sound is increased, and the amplitude decreases, resembling a siren. Resistor R3 limits the consumed current and made from a spiral cut for the hotplate.
Fig. 1. Schematic diagram of the electronic call
The device can be applied to the capacitors and resistors of any type. Transistors V1, V3, and V4 series MP39 - MP42, and V2 - series MP - MP by a factor of enhance current 20-60.
As the load you can use any small dynamic head the resistance of the voice coil is not more than 10 Ohms, for example, ADHD-6.
Power supply - battery "Krona" or two series-connected batteries 3336L.
Establishing device reduce to the selection of the value of the resistor R1 to obtain desired tone sound. The electronic bell (Fig. 2) is mounted in a small case. It is attached to the steering rod, and the button positioned at the brake handle.
Fig. 2. Wiring diagram
Authors: G. Makarov, A. Plotnikov