Photocell based night light
Description.
Many automatic night light circuits had been published here. This one uses a photocell for detecting the light intensity. At full light the resistance of the photocell will be few ten ohms and at darkness it will rise to several hundred ohms. The IC1 uA741 is wired as a comparator here. At darkness the resistance of photocell increases and so the voltage at the inverting input of the IC1 will be less than the reference voltage at the non inverting input. The output of the IC1 goes to positive saturation and it switches ON the transistor to activate the relay. By this way the lamp connected through the relay contact glows. The diode D1 works as a freewheeling diode.
Circuit diagram.
Notes.
- The circuit can be assembled on a Vero board.
- Use 9V DC for powering the circuit.
- POT R7 can be used to adjust the sensitivity of the circuit.
- The relay K1 can be a 9V, 200 Ohm SPDT type.
- L1 can be a 230V,60W lamp.
- R8 can be a ORP 12 photocell.
12V DC can also be used if 9V is unavailable. You will find that a 9V relay can quite happily operate from 12V and vice versa.
If uA741 is unavailable, use CA3140 as it is a uA741 pin for pin replacement.
R1 is to ensure that Q1 swithches off entirely and can be ommitted if required.
Q1 can be any NPN tranny as long as it can switch the current requirements of the relay.
All in all a very good little circuit.Very reliabe. I have been driving LED’s on my fish tank for about 3 years now with a very similar circuit.
please what is the difference between photocell and light dependent resistor?
2. also what are their similarities?
I am in need of a miniproject… can u send me any titles along with circuit within 2 days to my mail id.. plz…… am waiting for reply.. thanks in advance…
Am doing my Electronics and Communication Engg.. (B.Tech 3rd yr)..
nee project related to electronics side…
HI,
I HAVE BEEN ASKED TO DO A MINIPROJECT CALLED A CODED LIGHT FLASHER.IF ANYBODY CAN HELP ME OUT AND SEND ME THE CIRCUIT TO MY E-MAIL.
WAITTING FOR YOUR REPLAY
xx
FYI, I can’t see this correctly on the latest Halon browser.
I am in need of a electronics based miniproject… can u send me any links.please help me.
Read more: http://www.circuitstoday.com/photocell-based-night-light#ixzz0stCEz7oj
Under Creative Commons License: Attribution