Clap switch project file
CIRCUIT IDEAS
CLAP SWITCH
I
VED
DWI
S.C.
ere’s a clap switch free from false triggering. To turn on/off any ap pliance, you just have to clap twice. The cir-cuit changes its output state only when you clap twice within the set time period. Here, you’ve to clap within 3 seconds. The clap sound sensed by condenser microphone is amplified by transistor T1.
The amplified signal provides negative pulse
depending on the selected values of R7 and
C3. This ‘on’ time (T) of IC1 can be calculated using the following relationship:
T=1.1R7.C3
seconds where R7 is in ohms and C3 in microfarads.
On first clap, output pin 3 of IC1 goes high and remains in this standby position for the preset time. Also, LED1 glows for this period. The output of IC1 provides supply voltage to IC2 at its pins 8 and 4.
On second clap, a negative pulse triggers IC2 and its output pin 3 goes high for a time period depending on R9 and C5.
This provides a positive pulse at clock pin
14 of decade counter IC 4017 (IC3). Decade counter IC3 is wired here as a bistable. Each pulse applied at clock pin 14 changes the output state at pin 2 (Q1) of
IC3 because Q2 is connected to reset pin
15. The high output at pin 2 drives transistor T2 and also energises relay RL1. LED2
to pin 2 of IC1 and IC2, triggering both the
ICs. IC1, commonly used as a timer, is wired here as a monostable multivibrator.
Trigging of IC1 causes pin 3 to go high and it remains high for a certain time period
Now IC2 is ready to receive the triggering signal. Resistor R10 and capacitor C7 connected to pin 4 of IC2 prevent false triggering when IC1 provides the supply voltage to IC2 at first clap.
indicates activation of relay RL1 and on/off status of the appliance. A free-wheeling diode (D1) prevents damage of T2 when relay de-energises.
This circuit costs around Rs 80
CLAP SWITCH
I
VED
DWI
S.C.
ere’s a clap switch free from false triggering. To turn on/off any ap pliance, you just have to clap twice. The cir-cuit changes its output state only when you clap twice within the set time period. Here, you’ve to clap within 3 seconds. The clap sound sensed by condenser microphone is amplified by transistor T1.
The amplified signal provides negative pulse
depending on the selected values of R7 and
C3. This ‘on’ time (T) of IC1 can be calculated using the following relationship:
T=1.1R7.C3
seconds where R7 is in ohms and C3 in microfarads.
On first clap, output pin 3 of IC1 goes high and remains in this standby position for the preset time. Also, LED1 glows for this period. The output of IC1 provides supply voltage to IC2 at its pins 8 and 4.
On second clap, a negative pulse triggers IC2 and its output pin 3 goes high for a time period depending on R9 and C5.
This provides a positive pulse at clock pin
14 of decade counter IC 4017 (IC3). Decade counter IC3 is wired here as a bistable. Each pulse applied at clock pin 14 changes the output state at pin 2 (Q1) of
IC3 because Q2 is connected to reset pin
15. The high output at pin 2 drives transistor T2 and also energises relay RL1. LED2
to pin 2 of IC1 and IC2, triggering both the
ICs. IC1, commonly used as a timer, is wired here as a monostable multivibrator.
Trigging of IC1 causes pin 3 to go high and it remains high for a certain time period
Now IC2 is ready to receive the triggering signal. Resistor R10 and capacitor C7 connected to pin 4 of IC2 prevent false triggering when IC1 provides the supply voltage to IC2 at first clap.
indicates activation of relay RL1 and on/off status of the appliance. A free-wheeling diode (D1) prevents damage of T2 when relay de-energises.
This circuit costs around Rs 80