This circuit allows you to set a limit on the maximum output current available from your PSU. It`s very useful when you power-up a project for the first time - or carry out a soak-test. By setting an upper limit on the current available from your PSU - you can protect both your power supply - and any device connected to it. It offers a simple and
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cheap alternative to the Current Limiting Power Supply. The basic circuit is shown in the first schematic. The two diodes fix the voltage on the base of the Power Transistor at about 1v4. This means that the voltage across R2 is fixed at about 0v7. If R2 is 10 ohms, then the maximum emitter current is (0v7 G ½10) about 70mA. Since the collector current is always more or less equal to the emitter current - you cannot draw more than 70mA from the output terminals. If you try to do so - the output voltage will fall. I used a BD131 because that was what I had available. However, any NPN Power Transistor with a similar - or better - spec should work fine. I had no special reason for chosing a 70mA maximum. If you want to set a different current limit - change the value of R2. The formula is in the diagram. Always remember that if you increase the current - you`ll also increase the watts. The second schematic has a couple of added features. If you don`t want to use a voltmeter on the output - use an LED instead. If the output voltage falls - the LED will dim or extinguish completely. This is enough to let you know that the load on the output is excessive. Where the Current Limiter is to be left unattended for any length of time - say during a soak-test - the Buzzer is useful. Should a problem develope - and the output voltage fall by 2-volts or more - the circuit will sound the alarm. The layout provided is for the second...
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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