This article demonstrates basic circuits for pulsing infrared LEDs and low power visible semiconductor lasers using components which are inexpensive and fairly readily available. Many interesting and useful applications can be found in the references cited here, as well as several online web pages. This article focuses on the basic circuits. The i
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nfrared LEDS fabricated from GaAs or GaAlAs discussed here are PN semiconductor junction diodes fabricated from GaAlAs or GaAs and typically emit at wavelengths in the range 850 - 950 nm (with 880 and 915 nm being two readily available choices). Uses include infrared remote controls for consumer appliances. Typical specifications are DC optical power output ranging from 1 to 10 mW at DC forward currents of 20 to 100 mA with forward voltages from about 1. 3 to 1. 7 V. Considerably higher peak power outputs can be achieved if the LEDs are pulsed with short pulses in the range of 1 us to 100 us with low duty cycles of 1 to 10%. Optical pulse rise/fall times available from these LEDs range from ~ 500 ns to 20 ns (corresponding to bandwidths on the order of 1 MHz to 20 MHz). Visible semiconductor lasers found in common laser pointers emit at about 650 +- 20 nm and are commonly in the Class IIIA Laser Product category, emitting less than 5 mW under DC bias conditions from 4. 5 to 6. 0 V powered by three or four 1. 5V button cells. (Visible LEDS at this wavelength are also commonly used in audio digital optical output interfaces (S/PDIF) but power levels are only about 30 microWatts). Evidently the laser chips in most low cost laser pointers use no protection or biasing circuitry at all and the chips are reported to have modulation bandwidths of several hundred MHz extending the range of useful application considerably beyond that...
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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