I have made a simple project called automatic bathroom light timer off circuit its a very simple and easily made project.
Step 1: INTRODUCTION
Here is the simple and low cost automatic bathroom light circuit.The light automatically turns on when the bathroom door is opened and remains lit in occupied state when door is opened again the lamp turns off after a short delay .This automatic circuit saves energy and greatly asist your visitors especially at night.
Step 2: Schematic of the Automatic Bathroom Light Control Circuit
Here is the circuit diagram of the bathroom timer.The entire circuit is built around popular decade counter CD4017 (IC) and can be powered by any 5V DC/500mA mobile phone travel charger or adapter.
Step 3: WORKING OF THE CIRCUIT
The heart of this circuit is CD4017 CMOS counter with decoded output.On each pulse received on its clock input ,this IC drives high the next output.Output 0(pin 3)
of IC1 drives 1W light source (LED 2) through a driver transistor (T1)
Initially when the circuit is powered IC1 is resetted by the RC network and as a result LED1 lights up .When the door is opened for the first time, switch S1 is opened and as a result IC1 is clocked by the clock pulse generator.Now LED 1 goes off and LED2 lights up .IC1 stays in this condition to provide interior lighting even if the door is closed .However when the bathroom door is opened again IC1 is clocked again, and this resets the chip again by the signal from Output 2(pin4) of IC1 through D1 (1N4148)
Step 4: COMPONENT SELECTION
Regarding components selection it is not much critical.But try to use a good quality switch as S1 .the 3.6V/1W White LED current is limited by resistor R3
THE COMPONENTS USED ARE:
LED2 : 3.6V/1W White
C1,C2 :10 micro farad
S1 : N/O Push Switch
J1: DC Socket - PCB
Step 5: WORKING CIRCUIT DIAGRAM
Here is the final practical diagram of our circuit connected on breadboard.