An error amplifier is formed from Tr1 and Tr2, wired as a differential amplifier (often called a long-tailed pair - look at those collector leads). One input of this diff. amp is taken from the zener diode which provides a stable 4. 7 volts, the other diff. amp input is a fraction of the output. Any difference between the two will cause the curren
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t through R3 to alter and so will alter the voltage across it and hence to the base of Tr3. Tr3 and Tr4 are connected as a darlington pair, this produces a very high gain to aid stability of regulation. This darlington pair can be visualised as a single transistor connected in an `emitter-follower` configuration, the emitter voltage will follow the base voltage (less the 1. 2v required to forward bias the two base-emitter junctions), but with a much greater current capacity. Current limiting is provided by Tr5 which will be forward biassed by a fraction of the voltage drop across the current sensing resistor, R5, set by Vr1. As the current through R5 increases so does the voltage dropped across it, this begins to bias Tr5 on and in so doing causes Tr3/Tr4 to be deprived of base current and so reduces the output voltage. Tr4 needs a heatsink of at least 10 degrees C/Watt (10C / W) and R5 is expected to carry (1A * 4R) = 4 Watts, so it will need to be a 5W device or four 1R 1W devices in series, mount them on a peice of metal as they will get hot! As there is no current measurement built in to the unit, a useable scale could be marked around the potentiometer Vr1`s knob such that a known current could be chosen in advance of connecting a load. To do this, connect an ammeter directly across the power supplie`s output - this will instantly overload the supply and cause the current limiting to operate. Adjust Vr1 so that the...
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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