reflected infrared light switch
This circuit employs an infrared (IR) LED and a photodiode to create a simple yet effective switch mechanism. When a finger comes within approximately 1 inch of the sensor, it reflects the IR light emitted by the LED back toward the photodiode. The presence of this reflected light is detected by the photodiode, which generates a small current in response. This current is then processed to trigger a switching action, allowing the circuit to perform a specific function, such as turning on an LED or activating a relay.
The circuit operates efficiently with a low current draw of only 30 µA from a 3 V power supply, making it suitable for battery-operated devices where power conservation is critical. The choice of components, namely the infrared LED and photodiode, is crucial as they must be well-matched to ensure optimal performance. The LED should emit light at a wavelength that the photodiode can effectively detect, typically around 850 nm for common infrared applications.
In terms of implementation, the circuit can be designed on a printed circuit board (PCB) for compactness and reliability. Proper placement of the IR LED and photodiode is essential to maximize the detection range and ensure that the emitted light is efficiently reflected back to the photodiode. Additionally, the circuit may include a simple amplifier to boost the signal from the photodiode, enhancing sensitivity and allowing for greater detection distances.
Overall, this infrared switch circuit exemplifies a practical application of optical sensing technology, providing a low-power, effective solution for touchless activation in various electronic devices.Infrared light reflected off a finger is used to activate this switch circuit. Drawing only 30uA from a 3v supply, this circuit will detect a human finger with a range of about 1 inch. The sensor uses an inexpensive infrared LED and a matching photo diode. 🔗 External reference
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