Automatic washroom light switch


In this project, I will show you how to design and build a simple Automatic Washroom Light Switch Circuit, which will automatically turn on the when you enter the washroom and turns it off when you leave.

We turn on the lights in our washroom when we enter it and turn them off when we leave. Sometimes, we forget to turn the lights off after leaving the washroom.

This may lead to power wastage and also the lifetime of the light bulbs may decrease. To avoid these problems, I will show you how to make a simple circuit which will automatically turn the lights on when a person enters the washroom and it automatically turns it off when he/she leaves it.

By automating the process this way, there are many advantages like, the person need not care about turning the light on or off whenever he/she is using the washroom. The circuit, which you will know about in a moment, does it automatically for that person.
The circuit is also designed to consume lesser power so that the circuit can be used in any household or public washrooms without worrying about the power bill.


Before continuing with the working of the circuit, I will first explain the intended setup of this circuit. The reed switch is fixed to the wall near the door while the magnet is fixed to the door. This means that the reed switch will always be in closed state as the door is closed when the washroom is not in use (which is assumed as starting point) and the magnet will be near the switch. 

Assume you opened the door and entered into the washroom and then closed the door behind you. This action will make the switch open (when the door is opened first) and close (when you close the door). 

As a result, the output of the Op-amp goes HIGH (when you open the door)and then goes LOW (when you close the door). This in turn will cause the counter to produce a HIGH output at its Pin 2. Since Pin 2 of CD4017 is connected to the relay, the light will be turned ON. 

Now, when you are done with your business in the washroom, you will once again open the door, come out of the washroom and close the door. This action will once again cause the same action i.e. switch will open and close and output of Op-Amp will become HIGH and then LOW. 
But, since the Pin 4 of CD4017 is connected to the Reset pin, all the outputs will become LOW and hence the relay will be turned OFF, which in turn switches off the light.



  • No man power required.
  • Less Consumption of electrical energy.
  • Less maintenance.
  • Cheap and economical.

Leave a Comment