Dark sensor on breadboard

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dark-sensor1

Building a Circuit on Breadboard(Dark Detector using 2 transistors)
dark-sensor1Automatic-light-using-2-transistor

Get the following components:

NPN transistor- BC547 or BC147 or BC548

Take 2 transistors
transistors
transistor

Resistor- 1K

1K

 

Resistor- 330 Ohm
330R

Light emitting diode(LED)- Any color

LEDs

Connecting wires- Use single-core plastic-coated wire of 0.6mm diameter (the standard size)-You can use wire that is used for Computer Networking.

networking-wire

Power supply-6V or 9V


 Components for this experiment are available at buildcircuit.net.

components 2

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STEPS

Step 1: Put first transistor Q1-BC547 on breadboard as shown in the picture.

step1

Step 2: Put another transistor Q2- BC547 on breadboard as in step 1.

Step 3: Put wires across emitter pin of both transistors and -ve  terminal of battery(lowest/ bottom row of breadboard.)

STEP2Copy-of-step-4b

Step 4: Put a wire across Collector pin of transistor Q1 and Base pin of transistor Q2.

Step 5: Put a resistor 1K across positive terminal of battery(topmost row of breadboard) and Collector pin of transistor Q1.
Copy-of-step7b1

Step 6:Insert Light dependent resistor(LDR) across positive terminal of battery(topmost row of breadboard) and base terminal of transistor Q1.

step-6

Step 7: Put a resistor- 330 Ohm across base pin of transistor Q1 and negative terminal of battery(lowest bottom row of breadboard).

Copy-of-step7b1

Step 8: Put a resistor 330R across  positive terminal of battery(topmost row of breadboard)and anode terminal of LED(Light emitting diode) & Connect the cathode terminal of LED to Collector pin of transistor Q2.

Copy-of-step9b

The circuit is ready for testing. Connect battery terminals and see the output. As you block light falling on LDR(Light dependent resistor), the LED glows.

OUTPUT:

THIS CIRCUIT IS EXTREMELY SENSITIVE TO DARKNESS. EXPERIMENT THE CIRCUIT IN A HIGHLY ILLUMINATED ROOM.

LED GLOWS EVEN IN LESS DARKNESS. Use torch light if the LED glows in less darkness. You can adjust the sensitivity of the circuit using a variable resistor in place of R3-300 Ohm. Try this circuit with other resistances as well, for example, 1K, 10K and 100K, etc.


 

Components for this experiment are available at buildcircuit.net.

components 2

Buy now button


Automatic-light-using-2-transistor

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