Module Circuit light sensor with LDR (Light Dependent Resistor)


The example circuit used in various situations, such as control lamps or other device that needs to be turned off when the daylight. It is based on LDR (Light Dependent Resistor) is a special resistor that varies its electrical resistance according to the amount of light falling on its surface.

The circuit shown is easy to assemble and uses a light sensor ldr as the 10K potentiometer regulates the working point for your application. When light focuses on the LDR, the transistor turns on the relay that can handle various types of loads. As the LDR does not have a rapid response, rapid variations of light undetected, as lightning.

The LED serves to indicate the state of the circuit active or inactive and in many cases can be omitted by placing a jumper in place. To feed the circuit uses a 12 volts / 500mA power supply .

Diagram Schematic

Light Sensor Module Pcb Circuit Schematic

PCB for module light sensor

Light Sensor Module Pcb V1
Light Sensor Module Pcb V2
Light Sensor Module Pcb Layout
Light Sensor Module Pcb Silk



Resistor’s 1/4 watts 5%
R1 1.8KOhms – Black, Gray, Red, Gold
R2 680 Ohms – Blue, Gray, Brown, Gold
P1 10k – Trimpot
Q1 BC548 or equivalent – NPN Transistor
D1 1N4004 or equivalent – Diode
LED LED 5MM – Led.
VCC AK500/2 Power supply Connector
CN AK300/3 Load Connector
K1 Relay Onrom G5LE or equivalent
PCB, box, wires etc.

Download PCB in PDF format
Download PDF     Mirror

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About the author blog author. Electronics technician for the technical school of Brasilia - Brazil. Interested in electronics, circuits and technology in general.

13 thoughts on “Module Circuit light sensor with LDR (Light Dependent Resistor)”

  1. hello toni, i just wanted to ask on which output terminals of the relay will you put the motor that will serve as an output? C? NC? or NF? thanks in advance.

  2. haaiiiii,,
    my name is jared
    i want to ask to you
    how much input voltage??
    what is the function of the connector na, c, nf??
    how the voltage used on the relay??


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