Above is a schematic diagram of a type of audio oscillator known as a twin `T` phase shift oscillator. It gets its name from the phase shift network made up of R3, R4 and C3 plus C1, C2 and R2 which shifts the phase of the signal fed back from the collector to the base by 180 degrees for the feedback to make the oscillator oscillate. You will noti
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ce that the emitter of Q1 is not connected. Bringing this connection to ground will turn on the oscillator or "key it" as it`s called. You could connect this to a telegraph key and make a code practice oscillator. Now we need to be able to connect a speaker to it so we can hear the tone. To do this we need an audio amplifier, this is in order to have enough power from the oscillator to drive a small speaker. This part of the project uses an intergrated circuit or `IC` as the active component. IC`s contain many parts such as transistors, diodes and resistors all inside a very small package. This IC is designed to be an small low power audio amplifier and is not too easily damaged. Build these circuits one at a time or put them all on the same board. If you build them separately be sure to keep the connecting cables as short as possible. On the right is a diagram of the LM386 IC. Use this to find the correct pins to solder to. Actually, it`s best to use an IC socket and not to solder directly to the pins of the IC. Also make sure that all the grounds are tied together on all the boards if you do it in pieces. Government Surplus Auctions are an amazing source of cheap parts and good equipment! You might even find a car or a boat you always wanted for next to nothing! Get their list of auctions for your area. This is a little off the subject, but if you have ever heard of Nikola Tesla you might know about his involvement with...
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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