It is well known that through such simple everyday activities as walking on a carpet or moving in a chair, the body accumulates a static charge - sometimes many thousands of volts. Due to its extreme sensitivity, this circuit will detect not only such charges but also EMF-induced voltages in the body, which are generally far smaller. This means th
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at, whether you happen to be "charged up" on any particular day or not, your body will almost certainly trigger this circuit. An interesting twist is that the sensor does not need to be made of metal. Provided it is isolated from ground, the sensor can be any conductor, including a plant in a pot. The circuit is a comparator based on an LF351 FET-input op amp (IC1). The has the benefit of a high impedance input which is crucial for detecting a static charge. The other aspect which is crucial is that the 0V side of the circuit must be connected to earth (eg, a metal stake driven into the ground). Without the grounded connection, the circuit will yield poor results. Notice that the sensor connections are taken through diodes D1 and D2. This means that both negative and positive charges will cause the voltage at IC1`s inverting input to exceed that of the non-inverting input (the voltage at the inverting input rises or that at the non-inverting input falls). Trimpot VR1 and the two 470kO resistors across the supply are used to set the inverting and non-inverting inputs (pins 2 and 3) at around half-supply (ie, +2. 5V), while the two 470kO input resistors protect IC1 against damage from static. The sensitivity of the circuit is adjusted by VR1. While higher static charges will brightly flash the red LED, small and very rapid discharges through the sensor may barely illuminate it. The way around this is to feed the output at pin...
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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