The LX1970 light sensor can be used in conjunction with an LCD Front or Back Light Controller such as the LX1992 for LEDs or the LX1689 for CCFLs. This application note describes how to design in the LX1970.
Source: http://www.microsemi.com/micnotes/1403.pdf
This Circuit is easy, Light Relay Switch By BC547 & BC337.
Circuit Light Relay Switch By BC547 & BC337
PCB Light Relay Switch By BC547 & BC337
Circuit Precision LED Regulator by LM337T
I LED1 = 1.5V / R1
R2 Adjustable (+/-)15%
* ILED1 = 15mA , R1 = 100 OHM
Source :: http://www.zen22142.zen.co.uk/Circuits/Switching/darksw.htm
Circuit : Andy Collinson
Email: anc@mitedu.freeserve.co.uk
Description:
This circuit will activate a relay when light falls to a preset level. Light level can be adjusted with VR1 and the relay contacts may be used to operate an external light or buzzer.
Notes:
The light sensor used is the ORP12 photocell. In bright light the resistance of the ORP12 can be as low as 80 ohm and at 50lux (darkness) the resistance increases to over 1 Mohm. The 1M control should provide a wide range for light intensities, if not its value may be increased. The op-amp senses the voltage difference between pins 2 and 3. The control VR1 is adjusted so that the relay is off, the output of the op-amp will be around 2 Volts. When light falls, the resistance of the photocell increases and the difference in input voltage is amplified by the op-amp, the output will swing towards full supply and drive the transistor and relay. The 270k resistor provides a small amount of hysteresis, so that the circuit switches on and off with slightly different light levels. This eliminates relay chatter. Take great care if you decide to wire the relay to activate a mains lamp. Make sure the relay contacts provide adequate isolation and have ample rating for the load.
Parts List:
ORP12 Photocell (1)
RLY1: 12VSPDT (1)
U1: UA741 (1)
Q1: BC109 NPN (1)
D1: 1N4002 DIODE (1)
F1: 1A (1)
VR1: 1M RESISTOR (1)
ORP12: 500K RESISTOR (1)
R1,R3,R2: 10k RESISTOR (3)
R5: 4.7k RESISTOR (1)
R6: 1k RESISTOR (1)
R4: 270k RESISTOR (1)
Source :: http://www.zen22142.zen.co.uk/Circuits/Switching/ldet.htm
Kindly submitted by Mick Devine from the UK
Notes:
Variable resistor R1 adjusts the light threshold at which the circuit triggers. R1's value is chosen to match the photocells resistance at darkness. The circuit uses a CMOS 4001 IC. Gate U1a acts as the trigger, U1b and c form a latch. S1 resets the circuit. The output device may be a low power piezo buzzer.
Circuit Super Flashing Light by C1061
PCB Super Flashing Light by C1061
The LED voltage is buffered by a junction FET transistor and then applied to the inverting input of an op-amp with a gain of about 20. This produces a change of about 5 volts at the output from darkness to bright light. The 100K potentiometer can be set so that the output is around 7 volts in darkness and falls to about 2 volts in bright light.
source : http://ourworld.compuserve.com/homepages/Bill_Bowden/
As a keen cyclist I am always looking for ways to be seen at night. I wanted something that was a novelty and would catch the motorists eye. So looking around at my fellow cyclists rear lights, I came up with the idea of 'NITE-RIDER'. NINE extra bright LED's running from left to right and right to left continuously. It could be constructed with red LEDs for use on the rear of the bike or white LED's for an extra eye catcher on the front of the bike.
All IC's are CMOS devices so that a 9V PP3 battery can be used, and the current drawn is very low so that it will last as long as possible.
The circuit comprises of ...
1 555 timer IC4.
1 4027 flip flop IC1.
2 4017 Decade Counter IC2 and IC3.
3 4071 OR gate IC5, IC6 and IC7.
1 470 Ohm resistor 1/4 watt R3.
2 10K resistors 1/4 watt R1 and R2.
1 6.8UF Capasitor 16V C1.
9 Super brght LED's 1 to 9.
1 9V PP3 Battery.
1 single pole switch SW1.
1 Box.
How The Circuit Works.
IC4, C1, R1 and R2 are used for the clock pulse which is fed to both the counters IC2 and IC3 Pin 14.
IC1 is a Flip Flop and is used as a switch to enable ether IC2 or IC3 at pin 13.
IC7a detects when ether IC2 or IC3 has reached Q9 of the counter pin 11.
IC5, IC6 and IC7a protects the outputs of the counters IC2 and IC3 using OR gates which is then fed to the Anodes of the
LED's 1 to 9.
From : http://www.electronics-lab.com/
I ride my bike allot at night and sometimes I'm not sure if people can see me. This circuit will flash an incandescent light that you can purchase from Radio Shack. Adjust the VR's for your flash requirements and make sure that the lamp you use is designed to put out high brightness. The enclosure should be water tight. The Batteries can be replaced by a bike wheel generator and a diode. If you add the generator then you can still use rechargeable batteries and the batteries will charge while you are riding your bike.
From : http://home.maine.rr.com/randylinscott/mar20.htm
The way that this circuit works is as follows. The AC line voltage is rectified by D1 and D2 which connects to a voltage doubler circuit made up of the two 22uf capacitors. The Flash Freq. Pot and the 10uf capacitor charge up which triggers the Diac and causes the triac to turn on. This allows the trigger transformer T1 to send a very High Voltage to the flash tube and lighting it. The flash timing is adjusted by the flash freq. pot.
from ::http://home.maine.rr.com/randylinscott/sep99.htm
I have had many requests for this circuit. It was a very popular unit years ago. The basic idea of the project is to make different colored bulbs light at different frequencies of music. The circuit connects to the speaker outputs of your stereo or to the back of your speaker. The music passes through the transformer and the volume level is adjusted by the 5k ohm pot. Each light bulb is turn on by a different frequency of sound based on the resistor & capacitor combination in the gate circuit of the SCR. If the resistors R1, R2, or R3 are changed, the frequency of sound that will trigger the SCR will change. The isolation transformer is for protection.
From :: http://home.maine.rr.com/randylinscott/jan99.htm
This circuit was requested from an email. It will allow your car headlights to flash on and off at the same time or it will cause them to flash alternately. The circuit is based on the 555 timer. It is used in the astable mode. The 555 timer output will go high for an adjustable period of time and then turn off. It will then repeat the procedure. The time is adjusted by R1. To hook up the circuit to your car you must locate the positive wire from the fuse box to the headlights. Cut the wire and insert the relay contact and bypass switch. The bypass switch will allow you to bypass the relay contact for normal headlight operation. In the alternating headlight configuration you must cut the positive wire to each headlight and wire in the relay contact.
From :: http://home.maine.rr.com/randylinscott/sep98.htm
