This was a quick experimental prototype I put together based on an elegantly simple design by Doug Forbes, which uses common vacuum tubes. (Since Mr. Forbes`s original site is no longer available I have taken the liberty of reproducing his schematic and text above. ) In its simplest form a theremin works by mixing two high-frequency oscillators, on
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e fixed and one tuned by the capacitance of the player`s body, and extracting the audio-frequency difference between the two signals. Typically a second capacitively tuned oscillator is used to control the amplitude of the audio output. I had the requisite 12AU7 tubes and most of the other components already on hand, but had some difficulty finding information about the coils shown in the schematic. The solution is best summarized by this Usenet post from 2001: I`ve been working on an experimental model of this same circuit, and I was unable to find a value for the coil in question. I believe it`s available from Antique Electronic Supply as part no. P-C70-OSC, rather than PC-70-OS as listed in the accompanying text, but didn`t want to blow $7x3 to find out otherwise. So I read through the archive of the Levnet theremin enthusiast`s mailing list and found this message pertaining to the Forbes theremin schematic: ". Take a plastic film can-this will become your coil form. Use number 30 enamelled magnet wire (it winds very easily) and wind, in a single layer with the turns of wire laying neatly side by side, 66 turns of wire. Pull out some wire from the end of the winding (about five or six inches is fine), then with this "center tap" pulled out, continue winding an additional 33 turns of wire. Secure the ends of the coil, and the center taps, with silicon caulk. "The smaller coil (between the center tap and the end of the 33...
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....
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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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