Posts Tagged ‘lighting senser’

Using LED As A Light Sensor

This circuit shows how to use an ordinary LED as a light sensor. It makes use of the photovoltaic voltage developed across the LED when it is exposed to light. LEDs are cheaper than photodiodes and come with a built-in filter, which is useful when the application involves colour discrimination. The photo-voltage of a red LED (its bandgap voltage) is typically about 2V. The source impedance of this voltage is about 800M? in daylight, rising to infinity in darkness. A TL071 JFET input op amp is used to amplify and buffer this extremely high impedance signal.
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This is just over four times the 13mV maximum input offset of the TL071 op amp. R1 can be three 10M? resistors in series. Alternatively, I have found that a reverse-biased 1N4148 diode has an impedance of about 30M? (connect it in the circuit with the anode to ground). The output of the circuit is about 0V when the LED is in darkness. VR1 sets the gain of the op amp and it should be adjusted to give the required output voltage when the LED is exposed to bright light.
Author: Andrew Partridge – Copyright: Silicon Chip
Link : http://www.extremecircuits.net/

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solar cell LED lamp with LDR photo cell and extra capacitor

Reverse engineered circuit diagram of one more commercially produced solar lamp. This one is very similar to the one above, but it is brighter and contains an extra capacitor.

Read more original source: http://members.shaw.ca/novotill/SolarGardenLight/index.htm

6 Amp Solar Power Center by TLC2272

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).

Read more original source: http://www.solorb.com/elect/solarcirc/ccntlvd/