simple automatic street light system


Posted on Feb 5, 2014

The left hand side transistor T1 is rigged as a voltage comparator using a resistive network. The resistor at the upper arm is the LDR and the lower arm resistor is the preset which is used to set the threshold values or levels. T2 is arranged as an inverter, and inverts the response received from T1. Initially, assuming the light level is less, t


simple automatic street light system
Click here to download the full size of the above Circuit.

he LDR sustains a high resistance level across it, which does not allow enough current to reach the base of the transistor T1. This allows the potential level at the collector to saturate T2 and consequently the relay remains activated in this condition. When the light level increases and becomes sufficiently large on the LDR, its resistance level falls, this allows more current to pass through it which eventually reaches the base of T1. The transistor T1 conducts, pulling its collector potential to ground. This inhibits the conduction of the transistor T2, switching OFF its collector load relay and the connected lamp. The whole circuit can be built over a small piece of vero board and the entire assembly along with the power supply may be housed inside a sturdy little plastic box. The LDR must be placed outside the box, meaning its sensing surface should be exposed toward the ambient area from where the light level is required to be sensed.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    DC motor PWM speed control
    Line Powered Phone Messager (PIC16C819)
    Packet Radio with AVR
    Capacitor internal resistor meter
    Dual Power Supply 15V
    Acid rain monitor
    Variable Voltage Regulator
    Laptop Audio-Out Splitter
    Remote control using telephone
    The uTracer V3 a miniature Tube Curve Tracer
    12v 10 minute Off-Delay timer
    Gate automatic lamp circuit
    A 555 four-base integrated circuit delay circuits
    By setting the cutoff frequency of the programmable digital low-pass filter



    Top