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Clap Sensitive On-Off Relay(BC328)

2017-08-05 10:22  
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This article briefly describes the Clap Sensitive On-Off Relay (BC328). Although this circuit is very easy to understand, but also very practical. Circuit elements in depth understanding of the grasp of the principle is very effective. Do you know the circuit, you can see and purchase these components: BC328 .

3V Battery operated, Small portable unit

This circuit was intended to activate a relay by means of a hand clap. Further claps 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. Q1 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.

Figure:1 Clap Sensitive on-off Relay Circuit Diagram

Figure 1 Clap Sensitive on-off Relay Circuit Diagram


R1 = 12K
R2 = 1M
R3 = 6.8K
R4 = 220K
R5 = 2.2M
R7 = 100K
R8 = 22K
R9 = 6.8K
R10 = 100K
Q1 = BC550C
Q2 = BC328
Q3 = BC328
C1 = 220nF-63V
C2 = 22nF-63V
C3 = 220nF-63V
C4 = 22nF-63V
C5 = 22nF-63V
C6 = 47uF-25V
D1 = 1N4148
D2 = 1N4148
B1 = 3V Battery
IC1 = 7555 CMos IC
RL1 =DILReed-RelaySPDT
SW1 =SPSTSwitch
MIC1 = Electret Mic


A smallDIL5V 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.



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