|Parts Name||Parts Symbol||Parts Description||Quantity|
|Resistor||R1, R6||12K (1/4W)||2|
|Resistor||R3, R9||6K8 (1/4W)||2|
|Resistor||R7, R10||100K (1/4W)||2|
|Capacitor||C1, C3||220nF (63V, Polyester)||2|
|Capacitor||C2, C4, C5||22nF (63V, Polyester)||3|
|Capacitor||C6||47uF (25V, Electrolytic)||1|
|Capacitor||D1, D2||1N4148 (75V, 150mA)||2|
|Integrated Circuit||IC1||7555/TS555CN (CMos Timer IC)||1|
|Transistor||Q1||BC550C (45V, 100mA, Low noise High gain, NPN)||1|
|Transistor||Q2, Q3||BC328 (30V, 800mA, PNP)||2|
|Microphone||MIC1||Miniature electret microphone||1|
|Relay||RLY1||5V DIL Reed Relay (SPDT)||1|
This circuit was intended to activate a relay by means of a hand clap. A further clap will turn-off the relay. An interesting and unusual feature of this project is the 3V battery operation. The circuit's sensitivity was deliberately reduced, in order to avoid unpredictable operation. Therefore, a loud hand clap will be required to allow unfailing on-off switching.
CKT OperationQ1 acts as an audio amplifier. IC1 timer, wired as a monostable, provides a clean output signal and a reasonable time delay in order to allow proper switching of the following bistable circuit. A discrete-components circuit formed by Q2, Q3 and related parts was used for this purpose, in order to drive the Relay directly and to allow 3V supply operation.
- A small DIL 5V reed-relay was used in spite of the 3V supply. Several devices of this type were tested and it was found that all of them were able to switch-on with a coil voltage value comprised in the 1.9 - 2.1V range. Coil resistance values varied from 140 to 250 Ohm.
- Stand-by current consumption of the circuit is less than 1mA. When the Relay is energized, current drain rises to about 20mA.