Introduction:
In this Automatic street light circuit, we have demonstrated a Dark/Light Detector using a LM741 Op-Amp and LDR (Light Dependent Resistor). If the circuit fails to detect light, it triggers the IC and illuminates the LED attached to it. To use it as a dark detector alarm, we can also use a buzzer or speaker instead of LEDs. This LDR circuit is based on the LDR’s working and is quite simple. Let’s first learn more about LDRs.
Automatic Street Light circuit Making Video
Working Principle of Light Dependent Resistor
In this Automatic street light circuit, LDRs work based on photoconductivity, which is an optical phenomenon. A material’s conductivity increases when light is absorbed by it. When light falls on the LDR, the electrons in the valence band of the material are ready to move to the conduction band. In order to jump from one band to another (valance to conduction), the photons in the incident light must have energy greater than the bandgap of the material.
Hardware Components for Automatic Street Light circuit
| S.no | Components | Qty |
| 1. | Resistors – 220 Ohm, 10K ohms | 1,1 |
| 2. | Potentiometer – 10K ohms | 1 |
| 3. | Operational amplifier IC LM741 | 1 |
| 4. | LDR | 1 |
| 5. | 9 volts to 12 volts power supply | 1 |
| 6. | Breadboard | 1 |
| 7 | Hook up Wires |
User What is the difference between LM741 and UA741?
On the other hand, the UA741 is also an op-amp with similar specifications and performance to the LM741. Both the LM741 and UA741 have eight pins in a dual in-line package (DIP) format and are commonly used in a variety of analog circuit applications, such as amplifiers, filters, and signal conditioning circuits. They have been widely used in educational, industrial, and hobbyist projects
LM741 Op-amp IC
The LM741 operational amplifier is a DC-coupled high gain electronic voltage amplifier. There is only one op-amp inside. As a comparator, an operational amplifier IC compares two signals, an inverting and non-inverting signal. This IC performs mathematical operations in various circuits. An Op-amp is a voltage amplifier with a large gain. With a single or dual power supply voltage, the LM741 is able to operate.
LM741 Pin Configuration
| No. | Pin Label | Description |
|---|---|---|
| 1 | OFFSET NULL | Offset null pins for eliminating offset voltage and balancing input voltage |
| 2 | INPUT- | Inverting Input pin for Inverting signal Input |
| 3 | INPUT+ | Non-Inverting Input pin for Non-Inverting signal Input |
| 4 | V- | Negative or Ground supply voltage |
| 5 | OFFSET NULL | Offset null pins for eliminating offset voltage and balancing input voltage |
| 6 | OUTPUT | Output pin of the op-amp IC |
| 7 | V+ | Positive Supply Voltage |
| 8 | NC | Not connected |
LM741 Op-Amp
741 Op-Amp IC Specifications
| Parameter | Value |
|---|---|
| Minimum Power Consumption | ±10V |
| Normal Power Consumption | ±15V |
| Maximum Power Consumption | ±22V |
| Supply Current | 1.7 to 2.8mA |
| Input Impedance Range | About 2 megaohms |
| Output Impedance Range | About 75 ohms |
| Operating Temperature | -50 to 125 ˚C |
| Soldering Pin Temperature | PDIP package – 260 ˚C (10 seconds prescribed)<br>TO-99 and CDIP – 300 ˚C (10 seconds prescribed) |
Automatic Street Light circuit Circuit Diagram
