touch doorbell - electronic pushbutton

10-10 — elektor october 1980 touch doorbell electronic pushbutton Robert L.A. Trost Even the most futuristic doorbells - and quite a few have been published in Elektor in recent years — are operated by the familiar pushbutton. A modern doorbell which can play a melody or imitate a bird requires something a little more up-to-date. A touch switch would be more appropriate but for one reason or another is not usually thought of during the design. However, this article proposes to remedy this. The circuit diagram Figure 1 gives the circuit diagram of a universal touch switch which is particularly suitable for doorbells, but will be triggered. Its output then be- comes high causing T1 to conduct. If the sensor is released C3 is charged again and T1 will stop conducting. The touch switch has only two con- necting wires. These not only provide the switch with supply voltage, but are at the same time the switch connections. When transistor T1 conducts, the circuit will stop receiving ...