Introduction: Simple Mini Dusk to Dawn Switch for 220v AC

At or farms, we required to install a few lights that would

automatically turn on at night and turn off at dawn and since we required quite a few, it had to be cost effective and efficient. I thought about installing a timer switch at first but gave up on the idea. Finally after searching through numerous circuits the internet, I figured that an effective, small and cheap circuit could be designed with ease. The entire switch costs under 50 cents (Rupees 31/- in India). I extend my heartfelt thanks and gratitude to all the contributors of the many designs and circuits on the internet from where I have drawn the inspiration, the names of the contributors I do not individually know but my thanks to all.

Step 1: Parts List & Diagram

Parts Required Cost

1” x 1” Strip Board Rs.2/-

1 x BT136 or BTA12 Triac Rs.12/-

1 x DB3 Diac Re.1/-

1 x 1w. 100K Resistor Re.1/-

5mm LDR Rs.10/-

Assorted Wires for wiring Rs.2/-

Old Plastic Film Canister Rs.0/-

Total Parts Cost Rs.28/-


Soldering Iron

Solder Wire

Wire Strippers

Glue Gun

Assorted Small Tools


The circuit works on 220v AC and if you are not accustomed to working with mains voltage or do not have ample experience in working with 220v AC Mains Voltage please stay away from this project.

I assume no responsibility for any loss or damage arising directly out of or as a consequence of following this project.

It is always advised to take proper care and precaution while working with AC Mains.

Step 2: The Triac

Step 1.

Cut the strip board to the desired size and trim & file the edeges.

Place the BT136/BTA12 Triac through the holes in the center leaving a couple of lines on either side. Solder and trim.

Step 3: The Diac

Insert the Diac, 1 leg of the Diac should connect to the

Gate of the Triac and the other leg to an empty strip on the strip board, solder and trim.

Step 4: The LDR

Insert the LDR, one leg of the LDR should connect to T1

or M1 of the Triac and the other to the same strip to which the second leg of the Diac is connected, solder and trim.

Step 5: The Resistor

Insert the Resistor as shown in the picture, the first

leg should be connected to the same strip on which the second legs of the Diac and the LDR are connected and the second leg, place across the Triac and connect to an empty strip on the strip board, solder and trim.

Step 6: The Mains Connection

Now connect the Mains Connection Wires.

Connect 2 wires, preferably of the same colour (I have used Black & blue)to the strip on the strip board on which the second leg of the Resistor is connected.

Connect 1 wire (RED) to the strip on the strip board on which the 1st leg (M1) of the Triac is connected

Connect 1 wire (WHITE) to the strip on the strip board on which the 2nd leg (M2) of the Triac is connected. Solder and trim as required

Refer to the drawing for the connections.

Mains Connections –

The Black Wire and the Red Wire go to the Mains AC Supply, this is the input.

The remaining two wires (White & Blue) go to the BULB

Step 7: Done

You can seal the entire circuit in a small plastic

translucent film canister which will keep the water out and also let the LDR function normally in outdoor use.

Thanks for viewing, I must add here that I have been using these circuits on the lamp-posts at our farms for the past couple of months now and they have been connected ever since and I have never had reason to complain as yet. We do have regular power outages for around 4 to 6 hours a day a and that is probably the only rest the circuit gets. Otherwise, the circuit is working as it was intended to and every evening the lights go on and at day break they turn off automatically. I will post pictures of the working lamp-posts ASAP.