$0.1 Dusk to Dawn Switch Low Cost Simple Dusk to Dawn Switch Dark Sensing Light Automatic Lights

Introduction: $0.1 Dusk to Dawn Switch Low Cost Simple Dusk to Dawn Switch Dark Sensing Light Automatic Lights

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Turn your security lighting or task lighting on and off automatically each night with this circuit. It's easy to install.

Step 1: Components List

1. TRIAC BT136 or BTA16

2. LDR

3. 104 (0.1uF) Capacitor

4. 1K Ohm 1/4 Watt Resistor

5. DB3 Diac

6. Connecting Wires

Step 2: Connection Diagram

Make connections as shown in circuit, for more details Visit Link blog.circuits4you.com

Step 3: Test Your Circuit

1. Warning This Circuit Operates at AC 120V or 230V

2. Connect This circuit in series with lamp as Shown in Circuit diagram.

3. Take care that Lamp Light should not fall on LDR, This can cause false turn off or looping oscillations.

4. Save energy Go green..

5. Find difficulty in building circuit comment me on my blog.circuits4you.com

Home Automation

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Question 1 year ago on Introduction

Would this work with a 12 volt power supply. If not what would need to do change it to work with 12 volt power supply. Thanks


Reply 2 years ago

So did this actually work. Everyone else seems to claim it doesn't. It seems like a great solution to my problem of a high power instant acting dusk to dawn sensor.


4 years ago

Not working !!!


6 years ago

What exactly does a Triac do? I've heard people use them in place of Relays but you have to be careful with them. It looks like a mosfet / transitor but it can handle AC voltage. Aren't you supposed to put a diode between the output of the Triac and the second Mains wire?

Komal Manoj Thakur
Komal Manoj Thakur

Reply 6 years ago on Introduction

TRIAC is a device that will acts as relay, Semiconductor Switch. It can handle 400V AC 16Amps (BTA16) More than enough. No need of diode, we want to pass the AC supply. It works on basic principle, LDR when Light is more the resistance of LDR becomes low, so the charging of capacitor voltage is not enough to trigger the TRIAC. So it remains off during day time. At night LDR resistance become high and allows capacitor to charge above TRAIC triggering voltage threshold so Lights are on at night.