Schematics > Security and other sensors and detectors > Light Barrier Detector
Light Barrier Detector
This simple circuit using a single transistor turns ON the relay when light
falls on the LDR.
The potentiometer is adjusted for the required sensitivity.
The power supply is 6V.
Be careful about the impedance of the relay. Its impedance should not be less
that 60ohm.
Its working can be explained as follows:
With the light falling on the LDR,its resistance is low and the transistor is
saturated and turns the relay ON.
When light is obstructed, the LDRs resistance becomes very high. The
potentiometer shorts the transistors
base to ground and it is cut off. Hence the relay is OFF.
Tested 11th Jan,2001 by Naveen P Nwebmaster@electronic-circuits-diagrams.com
Title: Light Barrier Detector
Source: www.electronic-circuits-diagrams.com
Published on: 2005-02-09
Reads: 421
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