This circuit represents another version of an Armstrong Oscillator. This particular example uses a crystal in addition to the LC tank circuit used by the previous Series-Fed Armstrong Oscillator. By definition the Armstrong Oscillator uses a tickler coil for feedback, from the tuned circuit, as seen in the schematic. This oscillator is the shunt-
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fed type, using a separate path for the supply voltage and bypassing the tank circuit. This circuit version uses a PNP transistor as the amplifier. Virtually any PNP transistor may be used as long as it exhibits gain at the desired frequency of operation. Either a 2N3904 PNP Transistor or 2N3906 PNP Transistor may be used and both offer operation over 100MHz. The only important criteria is that the transistor provides amplification in the frequency range of oscillation. Because this is a PNP transistor, the supply voltage [Vcc] is reversed from the previous circuit. The frequency of the circuit operates at the frequency of the crystal, changing the crystal changes the frequency. Refer to this page for Crystal Oscillator Vendors. Transformer T1 operates as both an inductor in the tank circuit [T1 & C1] and the tickler coil, providing feedback from the output circuit [collector] to the input circuit [base] of the transistor. Of course the windings of the transformer are coupled together providing the regenerative feedback the circuit requires to oscillate [180 degree phase shift]. Note that the crystal is in series with the ticker coil. The variable capacitor C1 makes the tank circuit tunable. There are a number of possible styles of Trimmer Capacitors, and a number of different Manufacturers making Trimmer Capacitors. The tank circuit is the frequency determining component of the oscillator. The frequency of oscillation is...
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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