Electronic Projects | Electronic Circuits

 

 

 

Automatic light schematic

In above circuit R1 can be used to adjust the sensitivity. And the working of the circuit is very simple. The LDR will have very low resistance during day time so the transistor Q1 will be in OFF condition. And during night time the resistance will be very high so automatically the transistor Q1 will be ON.

The Q1 is PNP transistor and the emitter of Q1 is given to base of Q2. So the Q2 transistor will be ON only if the transistor Q1 is ON. The TRIAC is used in the circuit to make is circuit complete. As the TRIAC will allow voltage to pass from either directions only when there is a certain threshold voltage in gate terminal. And the gate of TRIAC is controlled by transistor Q2.

So totally the lamp will be ON during night time and will be again switched off during day light. To change the sensitivity of the circuit to light adjust R2.

If you have any doubts, do not hesitate to comment below. We will come to you with an appropriate solution.

 

Automatic Light Switch with PhotoTransistor

This is an automatic light switch circuit that turns ON a light bulb in absence of light. The IC 4060 works as an oscillator and generates a signal that is applied to the base of T4 transistor. Phototransistor T3 BPW40 is in conduction when light is present and it keeps the T5 transistor’s base at ground potential.

When light goes out and it doesn’t reaches the phototransistor, it gets in insulation. T3 reaches positive potential through 22kohm. T4 and T5 both gets in conductance. The oscillator signal reaches the optic coupler and then turns on the lamp.

 

3V to 9V DC Converters

 Here are some 3V to 9V DC converter circuits that were requested by some of our visitors. It may be helpful to have one of this converters when no 9V battery is available or if you consider that they are too expensive. The first circuit is very simple, it uses the TL496 power supply controller, a coil and a electrolytic capacitor.
  TL496 3 to 9 volt converter circuit
The maximum output voltage is actually 8.6V and current is around 80mA.
The input current (the current drawn from the batteries) is 405mA at the maximum output current. Without load the current consumption is 125µA and the batteries life is around 166 days.
Here is another 1.5… 4.5V to 9V converter

3 volt to 9 volt with LMC555
This dc converter is built with the CMOS version of 555 timer. You can get 12V too if you change the zener diode to a 12V version.

Probably there are more 3 to 9 volt dc converters but for the moment those are the only ones presented in this article.