Using LDR Dark Circuits With Transistors or Resistor

The LDR (Light Dependent Resistor) can be used in transistor or Resistance circuits to turn on and off an LED

The supplies used for the circuits are ;

for the Transistor circuit ;

3 ;220 Resistors

3.3 volt power supply

1 ;NPN 2222 transistor

1 LDR

for the resistor circuit ;

3.3 Volt power supply from Arduino

1 LDR

3 ;220 Resistors

multimeter

The supplies used for the circuits are ;

for the Transistor circuit ;

3 ;220 Resistors

3.3 volt power supply

1 ;NPN 2222 transistor

1 LDR

for the resistor circuit ;

3.3 Volt power supply from Arduino

1 LDR

3 ;220 Resistors

multimeter

The LDR circuit with transistors is a simple circuit .The transistors can act as an amplifier or a switch .

In this circuit, it is acting as a switch .The LDR resistor (Light Dependent Resistor) changes its resistance based on light intensity. The LDR will turn the transistor on in the dark .See the 1st and 3rd photo above .The LED is on in the dark .When the LDR is exposed to full light, the transistor turns off .See the second and fourth pictures .The LED is off .

The LDR circuit with resistors is a similar circuit .When the LDR is in the dark the LDR acts as a switch and turns the LED on .When the LDR is exposed to full light the LDR turns the LED off .Also note the voltage across the circuit in each case .

These are the pictures of the LDR circuit .I used Tinkercad to help see the wiring and positions of the components.

LDR circuits are used in home settings and industrial setting also to turn lights on and off ,but the voltages are higher and component are appropriate for the higher voltages .

I use the transistor circuit as a night light in my room.

I hope this helps you to understand LDR circuits better