In the project LED Touch Sensing by Jeff Han, I saw a magic happen on a LED matrix. That LED matrix not only lighted but also sensed the touch of fingers. At first, I thought there should be some secret behind and the LED matrix he used must be a special one. After discussing and simple trial with Tom Igoe, I found that any LED could be used as photdiode! Actually, the
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LED, as its name (Light Emitting Diode) implies, is electrically a diode and can be used as a detection device similar to a photodiode. But there are some restrictions: LEDs will only detect light of wavelength shorter than the wavelength of light that the LED would emit if it was put in a circuit that forward biased the LED. To use the LED as an optical detector, do not forward bias the LED into quadrant # 1 of the current-voltage (I-V). (Quadrant 1 is when the operating voltage and current are both positive. ) Allow the LED to operate in the solar cell mode, quadrant #4 (operating voltage is positive, current is negative), or in the photodiode mode quadrant #3 (operating voltage is positive, current is negative - ). I am also working on touch panel simultaneously as an input device for my project daPass. However, I prefer to use LED which can be both input and output device for my project if I can conquer hopefully. The test is doing when I cover the poarta. 0 LED dark enough (seria data value <= 2), tehn the LED on portb. 7 will be triggered to light up. Porta. 0 LED is reversed by its pins to get negative voltage. Below is my code: DEFINE OSC 4 TRISA = %11111111 ADCON1 = %10000010 tx var portc. 6 rx var portc. 7 n9600 con 16468 adcVar var word main adcin 0, adcVar serout2 tx, n9600, [DEC adcVar, 13] if adcVar<=2 then high portb. 7 else low portb. 7 endif pause 100 goto main In this step, I used 2x2 LED matrix as...
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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