Light

This page shows different ways to improve the response time of a photo transistor circuit...

The circuit uses a very inexpensive C-MOS IC that is connected to a small photodiode. Using a unique inductive feedback network, the circuit provides high sensitivity under high ambient light conditions. It is a great circuit when you want to extend the range of an optical remote control transmitter...

This circuit has a very low standby current requirement yet has very high sensitivity toward the light flashes from a xenon lamp. When connected to a flip/flop it can serve as an on on/off controller...

This circuit is a simple visible light or IR detector for testing any equipment which outputs light. The circuit can be also used for measuring ambient light levels. This circuit is based on one photodiode which is used in photocell mode so that the photodiode generates a voltage and current signal when it get light...

How do we achive 10nA operation? By using diodes in place of pull up resistors, and by isolating the DC load from the trigger circuit via junction drops and the 10nF capacitor. If there is too much power comming from the solar cell then the motor might run too often or even continuously. You can avoid this by putting a 100K ohm resistor in series with the solar cell...

Reverse engineered circuit diagram of a popular mass produced solar light. The light automatically turns on when there is no light falling upon the solar cell, so the parts count is minimal. The charging circiut is not particularly efficient since the battery must charge through a plain diode...

The Sun-Up Alarm can be used to provide a audible alarm for when the sun comes up or it can be used in a dark area and detect when a light comes on. It can also be used to detect a light beam, headlights etc. The circuit works as follows. The phototransistor is very sensitive to light. (Any phototransistor will work fine) The sun shining on this device will provide a high to one of the NAND gates. This will cause another NAND gate to oscillate which will drive another gate to output a 100hz tone. The transistor provides drive for the speaker...

A pair of LEDs having different wavelengths can supply the stimulus for a rudimentary spectral analysis during quality-control sorting operations. By measuring the reflectance of each LED, the circuit in Fig 1 can provide information about the spectral response of the object under test. The circuit`s operation is akin to the human eye`s using three receptors to deduce information about the entire visible spectrum...

The circuit on this page is for a simple light detector circuit board that has 8 detectors that can be used with visible or infrared light systems. The detectors use LM339 voltage comparators as the active element. Phototransistors or CdS photocells can be used as sensors for this circuit. If phototransistors are used the circuits can also be used as infrared light detectors. These detectors can be used as part of other light detector circuits shown on other pages at this site such as these Light Activated Detector Circuits at this site...

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...

This circuit is used to measure the current from a solar panel. It has very low power loss for currents in the 0-10A range. It also works as a general purpose DC current meter. The circuit can be used on either the positive or negative side of a DC circuit...

The SPC2 is a solar power center, it can be used to handle all of the power functions for small 12 Volt solar powered devices. It contains a photovoltaic charge controller and a low voltage load disconnect circuit. The low voltage disconnect has a load on-off switch, and a battery low voltage indicator. By using the SPC2 as the center of a solar powered device, long battery life is assured. The SPC2 is primarily designed to be a solar lighting controller, it can be used to power radios and other high capacitance loads with a minor switch and circuit modification (shown in dotted lines on the schematic)...