Introduction: Automated Lamp Using Op Amp 741 and LDR

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On the occasion of this design task, an automatic lamp based on a light sensor where the system can distinguish dark and light through the LDR or Photoresistor sensor.

Supplies

  • 1 LDR/Photoresistor
  • 2 1kΩ resistors
  • 1 Potentiometer/Variable resistor
  • 2 9V batteries
  • 1 Op Amp 741 IC
  • 1 Diode (1N5819)
  • 1 PNP Transistor (BC557)
  • 1 5V SPDT Relay (hk4100f-dc5v-shg)
  • 1 Bulb/ LED
  • Jumper wires
  • 1 Breadboard

Step 1: Objectives of the System

1) Help and lighten the workload of humans in the future in managing simple lamps.

2) As a solution to save power during the day because the lights will automatically turn off during the day.

3) Can be applied to street lamps and vehicle lamps.

Step 2: Base Theory

The base of the circuit is an Op Amp 741 which is used as a voltage comparator here. The R1 and LDR is used as the inverting input and the Potentiometer/Variable Resistor is used as the non-inverting input for the Op Amp. The Op Amp then sends the output to the transistor where it will determine whether the relay will switch or not depending on the inputs entering the Op Amp.

Step 3: Schematic

Step 4: Block Diagram

Step 5: Flowchart

Step 6: Simulation Circuit

Step 7: Place Breadboard and Connect Both Positive Rails and Negative Rails Together

Step 8: Place Op Amp on the Breadboard. the Orientation of the Op Amp Can Be Seen by the Dot Being on the Left Side

Step 9: Place Resistor and LDR and Connect Them to the Positive and Negative Rail on the Breadboard

Step 10: Connect Them to Pin 2 (inverting) of the Op Amp. the Pins of the Op Amp Is As Seen.

Step 11: Connect Potentiometer and Connect the Output Pin (middle) to Pin 3 (non-inverting) of the Op Amp. Connect the Other Two Pins to Power Rail and Ground Rail

Step 12: Connect Pin 7 of the Op Amp to the Positive Rail and Connect and Pin 4 to the Negative Rail

Step 13: Connect Pin 6 of the Op Amp to a 1k Resistor and Connect the Other End to Pin 2 (base) of the PNP Transistor. Connect the First Pin (collector) to Negative Rail. Transistor Pins Are As Seen in the Diagram.

Step 14: Connect Diode With the Gray Stripe Facing Upwards and Connect the Top Part to Positive Rail and Connect the Bottom Part to Pin 3 (emitter) of the Transistor.

Step 15: Place the Relay to the Breadboard and Connect the Top and Bottom Part of the Diode to the Coil Pin on the Relay. Relay Pins Are As Seen in the Diagram

Step 16: Connect N/O (Normally Open) Pin of the Relay to the Positive Wire of the Bulb.

Step 17: Connect 9V Battery With the Red Wire Connected to the COMMON Pin of the Relay and the Black Wire Connected to the Black Wire of the Bulb.

Step 18: Connect a 9V Battery to the Breadboard. and Now Set the Amount of Darkness Needed to Activate the Circuit With the Potentiometer.

Step 19: Youtube Video Link : Https://youtu.be/22GbMnEBXis

Step 20: References

Relay diagram: https://abra-electronics.com/electromechanical/rel...

Op Amp diagram: https://www.bragitoff.com/2016/02/op-amp-741-ic-pi...

Transistor diagram: https://www.el-component.com/bipolar-transistors/b...