I keep forgetting to switch-off bathroom lights and my wife loves to remind me"you left the lights on again ". So built this simple motion sensor switch that detects that I have done my business and no longer in the room, switches off light. There are many complex circuits out there. I hope I may have simplified them a bit.
And Yes it can be easily bought on Ebay, but I still wanted to do it
Step 1: What Do You Need ?
- Universal PCB
- PIR Motion Senor ( used with Arduino)
- Resister : 1 K Ohms
- Old 220V to 6V adaptor ( I used mine from old moto charger)
- NPN Transister 2N2222
- IN7001 diode for low noise
- Relay 6V, 5A 220V
- Some kind of Housing
I got my Motion senor from Aliexpress for about a dollar and have used my old Moto mobile charger.
Choose relay to support the load, I wanted to connect 15 Watts CFL ( 600mA, 220V)
CAUTION : There part AC 220V involved. Please seek professional assistance. I am not responsible if some one hurt themselves or hurt others or cause damage of any kind to their homes, following this instructions
Step 2: Circuit and Sensor
The motion senor can take input from 3V to 20 V,. When is senses motion the output pin is set to 3.2V.
Connecting Relay directly to motion sensor is not recommended, So using NPN transistor as switch and 1K resister to prevent current in opposite direction
To avoid spikes / noise, connecting a Diode across Relay.
Step 3: Build It
I have used old charger and tied the AC and DC cables separately. This helps in identifying AC / DC parts of the circuit
I used Connectors for AC input and AC output for easly installation
Connecting Motion sensor needs to be flexible so made a 3 pin connector
Step 4: Assembly
In my first attempt, I used old Laptop charger housing, but was not able to fit in. So had to borrow one of the cold cream boxes, It had excess space. Works good
In future I want fit it is small boxes.....
Step 5: Test It
Simply connect a Bulb socket and AC plug to it and test it
In the video, timer is set to few seconds and can be adjusted