LDR Based Project with Example

 

In this tutorial we are going to learn about LDR Based Project with Example

Circuit for LDR Based Project with Example

Below BOM for LDR Based LEDs strip ON & OFF

No. Qty Location Part No. Description
1 1 B1 9V (BATTERY CELL)
2 1 Q1 BD140 (PNP Transistor)
3 1 D1—D4 LNJ31LGKGXL (5MM GREEN LED)
4 1 LDR1 NSL 4962 (LIGHT DEPENDENT RESISTOR)
5 1 R1 2.7K/1/4W (Normal resistor 1/4W)

Construction of LEDs Strip ON & OFF
As per circuit diagram we can see first DC input source B1 which connected terminal are connected to LEDS strip of negative and positive are connected with emitter of BD140 with LDR1 and collector of PNP is connected to LEDs positive terminal. Base of transistor PNP is connected to LDR and series with 2.7K resistor which are connected to negative terminal of B1 battery.

Working of Circuit for LEDs Strip ON & OFF
First schematic as per below when LDR is not put under light then LEDs are showing OFF all components are connected to each other but still LEDs are OFF because in that situation transistor is OFF not getting any pulse so there is OFF state condition.


As per below schematic is second condition when LDR is get light then it will be generate light pulse due to that transistor get pulse and now current flow in collector side through emitter which are connected to LEDs positive terminal now LEDs will be ON as per showing below circuit.

Here below is second project

Below BOM for LDR Based Automatic street Light ON & OFF.

No. Qty Location Part No. Description
1 1 AC1 220 VAC (AC voltage Source)
2 1 Q1 BT136 (TRIAC)
3 1 Q2 DB3 (DIAC)
4 1 LDR1 NSL 4962 (LIGHT DEPENDENT RESISTOR)
5 1 R5 220K/1/4W (Normal resistor 1/4W)

6 1 DS1 BULB 100W (Normal Bulb)

Construction of Automatic Bulb ON & OFF
As per circuit diagram we can see first AC input source A1 which connected terminal are connected to Bulb and second terminal are connected with LDR1 with BT136 A1 and BT 136 A2 is connected to Bulb Second terminal with 220K resistance that are connected DB3 DIAC and DB3 second terminal are connected to BT136 gate.

Working of Automatic Bulb ON & OFF
when LDR is not put under light then Bulb are showing OFF all components are connected to each other but still Bulb are OFF because in that situation AC source are not completed because that second terminal connected to bulb through TRAI.

Second condition when LDR is get light then it will be generate light pulse due to that TRIAC get pulse and now current flow in TRIAC that control by DB3 and make completed circuit to bulb then current will flow in bulb then it will be on when LDR is get light and when LDR is not get any light then BULB will be OFF this is the function of automatic street light ON & OFF which are based on LDR.

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