2B-AUTOMATIC NIGHT LAMP
In the modern electronic age with the development and changes in this field a lot of project about cordless automotive type have come-up. This project is used at a place where light is required when sun sets. This project is very useful for the home when a bulb connected in this circuit comes ON whenever sun sets. For the electric supply people when evening sets, the street light should be ON or the garage where cars are kept we have to search for the light switch while taking car IN or OUT. By putting the automatic night lamp in a secret place, it informs about the entrance of new comer.
TECHNICAL DESCRIPTION AND WORKING
This project has been developed and tested O.K. in our TV Engineers Technical Lab. The components and PCB used in the projects published in our books are available for sale at resonable price.
In this project LDR has been used. The full name of LDR is light dependent resistance. The value of the resistance depends upon the amount of light falling on it. Its value decreases in the light and in dark resistance of LDR increases. This LDR has been used in the input of operational amplifier IC741. There are two inputs in this amplifier. One is given +ve Voltage whereas in another -ve voltage is given. Out of these two inputs that input having more DC voltage will amplify the signal and gives its output. In the circuit of this project input signal has been given to the pin no. 2. LDR whose value depends upon the light also connected to the input no. 2. In the second input on pin no. 3 voltages are not stable. When ever light falls on the LDR and its value decreases at that moment we get output voltage on pin no. 6. Pin no. 7 of IC are given +ve voltage and pin no. 4 has been grounded. The output voltage obtained at the output of this operational amplifier works as bias voltage for the transister BC558. The output of this transister is available on the collecter of this transister and through a diode and a preset it is connected to the gate of SCR. It get triggered on getting +ve voltage and this +ve voltage is controlled by the preset 20K. By adjusting the value of preset we keep SCR on the triggering point. SCR is a kind of a diode which is having the anode and a cathode and it allows to flow the current in one direction. But there is special point in it that it is having a gate electrode whereas in a diode it is not there. When gate is triggered it starts conducting. After that even when the +ve voltage is removed, it continuous. After that the lamp gets the supply voltage and it gets lighted.
PRECAUTIONS WHILE ASSEMBLING THE PROJECT:-
* First of all check the all components whether they are according to the project or not.
* While soldering give attention to the cleanliness. There should not be any short in the print or PCB.
* Use an IC Base.
* Use the value of the resistances as given in the circuit diagram.
* Check the anode and cathode of a Diode.
PCB [CODE 6TP02]=1
BEL188=1,SCR 604=1 , LDR =1
DIODE IN4007 =5
ZEENER 9V =1
15K=1, 10K=2, 2K7=1, 1K2=1, 33K/2W=1
Load or BULB [60Watt] =1