Saturday, February 11, 2012

circuit activate a relay by means of a hand clap

This circuit is intended to activate a relay by means of a hand clap. Further beats off of the relay. An unusual and interesting feature of this project is running on battery 3V. The sensitivity of the circuit has been intentionally reduced, to avoid the unpredictable operation. Therefore, the clapping of hands will be stronger they need to allow a constant on-off. Q1 acts as an audio amplifier. Timer IC1, wired as a monostable, provides a clean output signal and a delay of a reasonable time, in order to allow correct switching of the bistable circuit following. A discrete circuit components formed by Q2, Q3 and related parties has been used for this purpose, in order to drive the relay directly and to allow the operation 3V power supply.
Circuit Diagram:
 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 = DIL Reed-Relay SPDT
SW1 = SPST Switch
MIC1 = Electret Mic


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. 
Source: Red Free Circuit Design
tags: power supply, battery, Timer


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