The project “Sound Activated 0-30 Minutes Timer Circuit” is a simple project designed using timer IC 555 and LM324 Quad op-amp IC. By using this project, one can activate or de-activate the appliance using sound and time delay can be adjusted from few seconds to 30 minutes.
Application: The applications of project is:
- Used as sound activated burglar alarm.
- Used as timer circuit in kitchen, house.
- used for appliance operation like refrigerator, TV, Rice-cooker etc. by adjusting the time as per required.
Circuit Description of Sound Activated 0-30 Minutes Timer Circuit:
The circuit of Sound Activated 0-30 Minutes Timer Circuit is shown in figure 1. The circuit is designed around Microphone, Quad op-amp LM324, IC555 and few other electronics components like resistors, capacitors, diode etc. for working flawlessly. For better understanding of project, the circuit is divided into three main section.
Sound Detector and Amplifier Section: The sound detector and amplifier section is designed around condenser microphone (MIC1) and Quad op-amp IC LM324. Microphone MIC1 detect sound signal (say clap sound) and change it into electrical signal. This electrical signal is very small and need further amplification. The work of amplification is done by one of the op-amp of quad op-amp LM324. The output of microphone is given to the inverting terminal of amplifier A1 through coupling capacitor C1. The sensitivity of microphone is adjusted using variable resistor VR1.
Timer Circuit: The output of amplifier from pin 1 is given to trigger pin (pin 2) of Timer IC 555 through coupling capacitor C3. The timer IC (555) is configured in monostable mutivibrator mode which is also called as one shot multivibrator. When microphone detect any sound signal, the output pin of IC1 becomes high and make trigger pin (pin 2) of IC2 high. The high at trigger pin set the internal flip-flop of IC2 and as a result the output at pin 3 become high. The time interval of the circuit Sound Activated 0-30 Minutes Timer Circuit is dependent of RC component connected to pin 7 and pin 8 of IC2 i.e. R5, VR2 and capacitor C4. By adjusting one of these three components the time interval changes. It is quite tedious to change the value of capacitor and fixed resistor. Thus, we had use a variable resistor to change the value of resistor and finally change the time interval.
Switching Circuit: The switching circuit is designed using a relay and diode. The relay is an electromagnetic device which uses low current electrical signal to current high power electrical appliance. The high output at pin 3 energize relay RL1 for time interval set by variable resistor VR2. Glowing LED1 indicates relay is energized (i.e. load is active), where resistor R6 is current limiting resistor which protects LED from burn out due to high current. Diode D2 is fly-back diode and protect the coil of relay. Load is connected to connector 2 (CON2) where AC mains is given to connector 3 (CON3). The DC power supply is connected to connector 1 (CON1).
NOTE: The voltage rating for relay must be same to DC power supply given to the circuit. If DC volt given to circuit is 6V then relay is also must be 6V. Similarly, if DC volt is of 12V then relay also must be of 12V.
PARTS LIST OF SOUND ACTIVATED 0-30V MINUTES TIMER CIRCUIT
|Resistors (all ¼-watt, ± 5% Carbon)|
|R1, R4 = 10 KΩ
R2, R5, R6 = 1 KΩ
R3 = 1 MΩ
VR1, VR2 = 1 MΩ
|C1, C3 = 0.1 µF (Ceramic Disc)
C2 = 10 µF/16V (Electrolytic Capacitor)
C4 = 100 µF/16V (Electrolytic Capacitor)
C5 = 0.01 µF (Ceramic Disc)
|IC1 = LM324
IC2 = NE555
D1, D2 = 1N4007
LED1 = 5mm any color LED
|RL1 = 6V – 12V Relay
MIC1 = Condenser Microphone
SW1 = ON/OFF Switch
CON1, CON2, CON3 = Two pin connector
Power Supply = 6V – 12V DC power supply