Automatic Street Light Dimmer Using Motion Sensor

“Save Energy For Future” one of the most common motto which we we’ve seen or heard throughout our life, Well, here we?will be?implementing it through this simple circuit. The power loss from street lights can be reduced to a large extent by implementing an automatic dimmer, which will reduce and increase the brightness automatically.

This smart automatic street light dimmer using motion sensor will save power by reducing it’s brightness. When someone passes the road, the PIR sensor will detect the motion on the road. The signal from the PIR sensor will activate the circuit and in turn increase the brightness. This street lamp circuit is not using microcontroller, making it cheaper and commercial. We can use this simple circuit for outdoor lighting.


Circuit Diagram of Led Street Light With Auto Intensity Control


Working Of Street Light Controller

  • This is a battery powered led street light with auto intensity control that operates with 5V DC.
  • To get a regulated 5V, we use 7805 regulator. A 0.1uF is connected in parallel to the regulated output to filter noise generated by the 7805 IC.
  • The main component of automatic street light dimmer is the PIR motion sensor. The out pin of motion sensor will be high (5V) when a motion is detected and it will automatically go low(0V) after a preset delay.
  • The output signal delay of PIR motion sensor can be varied by a preset attached with the PIR sensor.
  • Output pin of PIR sensor is connected to the base of a BC548 transistor through a 1K ohm resistor. So, as a result of the motion the NPN transistor BC548 will be ON and gets –ve or ground on the –ve terminal of LED, causing the LED to switch on with high brightness.
  • Also you can see a 10M ohm resistor is connected in series with 100K potentiometer(Volume control), there will be a voltage drop across 100K potentiometer, this voltage drop can be varied by turning the knob.
  • This voltage drop is fed to the base of transistor via 1N4148 diode, it turns ON transistor, but LED will glow with low brightness. We can adjust the drop voltage to switch on transistor by turning the knob, thus we can adjust the brightness.
  • 1N4148 diode is used to avoid reverse voltage from 1K ohm resistor. It will affect the base voltage to switch on LED in high brightness.
  • We can use this automatic street light as solar led street light by simply connecting solar panel as power source.

Components Required For Automatic Street Light Dimmer

  1. PIR Sensor
  2. Transistor (BC548)
  3. IC (7805)
  4. Resistor (10M, 1K, 100 ohm)
  5. Potentiometer (100K)
  6. Capacitor (0.1uF)
  7. LED (White x2)
  8. 9V Battery

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