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Simple Automatic Street Light Circuit Diagram

In this topic we study about how with can perform different mechanical work by machines. Don’t worry, in this topic we don’t use any programming style. We perform our task with the help of electricity. In this topic we make own automatic push up button. A question is rise in your mind “how it possible?” Let see in this topic. Therefore we need few electric components that help to perform this task.

The list of these components is given below:

  1. PCB ( printed circuit design ) or Breadboard
  2. 9v ( 9 volt ) battery
  3. Battery clipper
  4. Few LED ( light emitting diode )
  5. One 320Ω ( 320 ohm ) resistance
  6. One 220Ω ( 220 ohm ) resistance
  7. One BC547B transistor
  8. One LDR ( light dependent resistor )
  9. Few pieces of wires
  10. Solder
  11. Marker
  12. Active mind ( most important thing )

These are the things that we need for this project. We things are easily available in local hardware or electronic shop. First we study the circuit diagram of the automatic street light.

Circuit diagram for Automatic Street light:



This is a circuit diagram of Automatic Street light. Let try to understand this circuit. First start form battery. The positive side of the battery is divided into two directions. At first direction there is a resistor of 330 Ω and on the other direction 220 Ω resistor is connected. Don’t worry about negative side and the positive side of the resistor. Resistor is not polarity sensitive. After that there is LED is connected with 330 Ω resistor, but be care full the light emitting diode is polarity sensitive, so how you find the positive and negative terminal of light emitting diode. It is too much easy. Pick up the light emitting diode in front to you to feel that the legs of light emitting diode are not equal. This is the difference and way to identify the terminals of light emitting diode. The larger one is positive terminal and small one is negative terminal. Now you able to identify the terminal of light emitting diode then connect the positive terminal with 330 Ω resistor as shown are figure. Now come to the 220 Ω resistor, again resistor is not polarity sensitive. One side of this resistor is already connected with the battery, but the other side of resistor is connected to LDR sensor, LDR sensor is light dependent resistor, it can senses light. If light is present or not. Light dependent resistor is not polarity sensitive, so you can connect as you can. The other leg of light dependent resistor is connected to the negative side of battery. Now our circuit is all most create.


Automatic Switch:


Now we have to make automatic switch. To make this switch we need BC547B transistor. First of all we need to study about transistor and how to use? There are two type of transistor available in the market NPN and PNP transistors. In our cause we need NPN transistor. NPN transistor is divided into three parts first part is collector, base and emitter. In the NPN transistor cause collector and emitter are made from negative partial and base by positive partial. I hope that you will understand the structure of the NPN transistor. Let talk about the working of NPN, the working of the transistor is depending upon the condition. First you have to identify which are emitter, collector and base. The shortcut method to identify legs, the center leg is always indicating base. The emitter and collector are quite difficult, but not worry about it, pick up the transistor in front for you. You observer that the transistor is in D shape, so pick the plain area. The most left is emitter and you know the middle leg is base. The most right is collector. Now place plain shape toward the battery. The collector in connected with light emitting diode. The base is connected between 220 ohm resistor and light dependent resistor. The last one is emitting is connected with the negative side of the battery.

Working of automatic street light:

When we connect the positive terminal to the circuit that with have design. Current is passing and in the presences of light. LDR resistor is to high so path is not complete. Current try shot path then it move toward transistor. It is place forward bias. It dose not allow to flow current. So to flow current we have to apply have current on base for flow current, so we off the light. Resistance of LDR is low current will flow it and apply on base. When current is passes from base current will also flow have transistor then passes form led. LED is on, again when you on the light led off.

Dome Video of automatic street light:


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