How to make a circuit of Automatic Street Light control system?

Automatic street light system is very common nowadays as it provides intelligent street lighting mechanism. It provides light automatically during night without any human interference. These energy saving street lights make use of incandescent lamps instead of LEDs.So here I will teach you how to make an electronic circuit for street light automation. The heart of this circuit is a LDR (Light Depended Resistor) which is connected as a potential divider with a 56K resistor. The drop across LDR is used for switching the transistor. Solar led street lighting systems are the advanced versions of this ordinary automatic street light controller.

Circuit diagram of Automatic Street light using LDR

Street+Light How to make a circuit of Automatic Street Light control system?

Components Required

  1. Rectifier power supply (Step down transformer [1A], Diodes-4, Capacitor-470μF)
  2. LDR
  3. Resistors (56KΩ,100Ω)
  4. Transistor BC187 x 2
  5. 6V or 12V Relay
  6. Bulb

Working of Automatic Street Light circuit

  • The bulb should remain OFF during daytime and turn ON automatically during night.
  • The unique property of light depended resistor is utilized here. LDR is a variable resistor which has very low resistance in the presence of light and very high resistance in the absence of light.
  • In this circuit, we create a potential divider network with an ordinary resistor in one arm and a LDR on the other arm.
  • According to Ohm’s law (V=IR), voltage drop across the resistor increases when its resistance increases.
  • Here the drop across LDR varies with changes in light intensity. That is voltage drop across the LDR is minimum in the presence of light and maximum in the absence of light.
  • One end of the LDR is connected to the base of a BC 187 transistor. At night, the drop is very high (> 0.6V) and it is sufficient to turn on the transistor.
  • When the first transistor is ON next one will also turn ON. Thus the relay coil energizes and the bulb will glow.

Read further: How to connect relay: Relays working with animation

  • During day time the drop is very small (< 0.6V), so the transistor remains in OFF state.
  • The diode Df is the free wheeling diode used for decaying the energy stored in the relay coil when the circuit is switched off.

Components Pin out

21 thoughts on “How to make a circuit of Automatic Street Light control system?

  1. Hi Admin,

    Just want to clarify some point, on the schematic above the transistor is NPN type but I check the model BC187 is a PNP type.

    Kinly please clarify. Thanks.

  2. hi
    i like your project please introduce remote control circuit. some circuits are there but how put them off ?. hence show
    and send me remote control circuit which we can on and off with remote independently.
    thanks and regard

  3. Pls send me some pictorial diagram and assembled project of solar street lights of yours, thank you for the knowledge.

  4. Sir i want to know.how can i get all this components in the market.and sir can i use this circuit for 3kv To 5kv load.If yas then how sir send me circuit digram and video .

  5. Hi,

    This looks simple and I gave it a try to fix one at my home.

    It works normally when we I tested it out manually. But when the light goes down slowly, there occurs a flicker in the relay and nothing works after that.

    My components are still in good condition and this happens every evening. Any suggestions?

  6. Please clarify each junction of the diagram and state the market/place where the components may be purchased. How is the variation of the diagram and components in regards of different load?
    Thank you for your will and knowledge.

  7. Sir,how can I add timer circuit to this present one like say even if the sun rises at 6 in the morning, is there any possibility that I can make the LED glow till 8.I know that this idea would change the basic idea of this model itself but is there any possibility to get that required output…
    I thought of adding a capacitor having a sufficient time constant which could make that happen.Would that suffice sir??

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