The circuit on this page is for a visible and infrared light detector circuitboard that has 8 detectors. LM339 voltage comparators are the active element. 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. For phototransistors a valu
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e of 470K ohms will work for most room light situations. If the light is dim, selecting a higher value resistor such as 1Megohm will give better sensitivity. This High Impedance Test Voltmeter circuit can also be used for testing phototransistors installations. For CdS photocells it is usually best to install the cell and then measure its resistance under the normal lighting conditions. A resistor with a value that is 3 to 5 times the measured resistance of the cell is then selected for R1. A 1K ohm resistor will allow about 10 milliamps to flow through a typical LED if the supply voltage is 12 volts. The value of the resistors at the outputs of the comparators can changed depending on the desired current through the LEDs. The following diagram shows the circuit that is on the printed circuit board. There are 8 independent photo-detectors with open collector outputs that can sink up to 15 milliamps each. All of the comparators on the PCB are wired so that when the photosensors are exposed to light, the output of the comparators will be LOW and the LEDs will be ON. The detection voltage level for the circuit as shown is set at 1/2 of the supply voltage. If a lower or higher detection level voltage is needed, the values of resistors R9 / R10 and R19 / R20 can be adjusted. This circuit does not need a regulated power supply and can operate on supply voltages of up to 32 volts. For more general information on Voltage...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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