Periodically On Off Mosquito Repellent

Periodically On Off Mosquito Repellent

Summary

The circuit describes below can be used to on and off the electronic device. The time period for which device remains on is similar to the time period for which it remain off. Therefore we can use it in many applications like many of the mosquito repellent available in market use toxic material to kill mosquitoes which generate poisonous vapor to keep mosquito away from the room which is harmful for our body. Continuous release of vapor may harm our brain. Long exposure to these toxic vapors may cause neurological or related problems.  

Description

Here is a circuit that automatically switches on and off the mosquito repellent after preset time interval, thus controlling the release of toxic vapors into the room. The circuit turns the mosquito repellent periodically ‘on’ and ‘off’ for approximately 2 minutes 30 second each. You can also increase or decrease the time according to your requirement.

In this circuit pin 3 always oscillates back and forth from high to low during one cycle capacitor charge in on direction giving output and again charge in opposite direction to remain off. Consider the case when you on the circuit for first time at this time voltage at pin 3 is zero and voltage at pin 1 and 2 is high which is feed to pin 4 which is also high and pin 5 and 6 initially connected to pin 3 through capacitor and resistor are also low but after some time capacitor connected between pin 3 and 5 start charging with the help of C1 and R1 voltage at pin 3 also start building which is internally connected to pin 12 ad 13 as a result output pin 11 become low and this is supplied to pin 8 and 9 and pin 10 become high and we will get output means transistor start conducting. And the device connected to relay start operating.

After preset interval of time the polarity of the charge across C1 & R1 has reversed. Pin 4 is low and pin 3 is high. C1 again starts to charge once more. But this time in the opposite direction. Since pin 3 is now high and pin 4 is low the junction of C1 & R1 represents the negative side of the capacitor. As the capacitor charges the voltage on this junction will fall. This means that the voltage on pins 5 & 6 will fall. When it falls to just below half the supply voltage the inputs change from high to low. And the output of gate 2 will go high. Pin 4 will take pins 1 & 2 high. So pin 3 will go low.
In other words the first cycle is complete.

If you want to increase the time period just change the value of R1 and C1 and see the deference.

Components
IC
IC1(CD4011)	1
Resistor
R1(4.7M)	1
R2(1K)	1
Capacitor
C1(1uF)	1
Miscellaneous
Relay	1
T1(BC547)	1