Here`s something that might intrigue you Crystal Radio builders out there: A one-transistor (Silicon, yet!) AM broadcast receiver that derives its power from ambient AC hum and `spherics [static crashes]! Gotta give credit when I can: The germ of the schematic was borrowed from Darryl Boyd`s `Stay Tuned` website which features over 170 articles an
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d plans on crystal radio construction. The URL for the site is and my No-Power - or, more accurately, Free-Power - circuit was derived from #2 of the 3 circuits found in the site`s project #153, "How to Build Free-Power Radios. " That website has three jpeg pages which are copies of the original article, by Terry L. Lyon, from an old Popular Electronics magazine issue. The 2nd page is the page containing the 3 schematics of single-transistor, free-power receivers. My version has some modifications of the original circuit, which I will describe below. Terry Lyons` original circuit was designed around a common-emitter amplifier, with emitter grounded; mine has a 100K ohm potentiometer inserted between the emitter and ground. The wiper of the pot connects to a tap on the antenna coil, 5 turns up from ground, with the pot determining how much of the emitter current is permitted to flow through the coil winding in a Hartley Oscillator feedback configuration, so that a fraction of the incoming RF signal is fed back into itself after having been boosted by the transistor. With enough battery voltage present, advancing the pot to full clockwise would connect the transistor`s emitter directly to the coil tap, causing the circuit gain to increase through positive feedback (regeneration) until the circuit "plops" into oscillation at the tuned frequency. In our "free-power" receiver, there isn`t enough voltage or current to achieve...
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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