Nothing really new: a JFET is used to sense the electric field generated by high voltage electric line; the JFET amplifies the signal very little, but it lowers the impedence and provide current to a level suitable for transistor amplification. The two transistor can be any low power NPN scavenged from anywhere. The two-transistor are configured a
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s a sort of thresholded amplifier: when the voltage at R2 rises at above 3V circa, Q1 starts pumping current into the LED with a step curve providing a better go-no/go rensponse. The circuit is the same as the one used in the Korg Monotron to drive the LFO LED. A low current LED could have been connected directly between V+ and the Drain of the JFET and removing TR1, TR2 and R3 through R7: in this case the LED would light up in a linear way, no threshold. See bottom of post for a description of what TR2 is there for. Stray charge may escape from the tip of R1 for tip-effect letting the intrinsic capacitance at the gate of the JFET charge positively giving a positive read after a little while. So, a curled tip and a very high resistance path to ground in the form of a few turns of thin wire around resistor R1, help keep things in balance. In case, a very very high resistor can be connected between gate and ground (R8), but this will limit sensitivity very much. Resistor R1 is there to provide a protection to the delicate gate of the JFET and the delicate heart of the operator in case of contact to a live line. Here, the higher the value of the resistor, the better. R1 also provides for the sensing tip.
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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