Digital output from a microcontroller is typically a low-amperage signal. For example, when you put a pin HIGH on the microcontroller (in Wiring/Arduino, it`sG‚ digitalWrite(somePin, HIGH); ), the voltage coming from that pin is typically +3. 3V or +5V, and the amperage coming from it is typically 10 milliamps or less. This is fine if you`re contro
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lling an LED, whose required amperage is tiny. Most devices you`d want to control require more current than that. In order to control them, you need something in between your microcontroller and the device that can be controlled with this small voltage and amperage. Relays and switching transistors are most often used for this purpose. A relay is a switch that`s controlled by a small electric current. Relays take advantage of the fact that when you pass an electric current through a wire, a magnetic field is generated surrounding the wire as well. When you place an iron shaft inside a coil of wire and pass current through the wire, the magnetic field moves the iron shaft. If that iron shaft is part of a switch, the switch can be turned on and off by putting current through the coil, which moves the shaft, closing the contact (see diagram below). Note the diode in parallel with the load here. This is used only when the load is a motor, solenoid, or some other inductive load, and when it is switched off, will generate a blowback voltage. The diode protects against this. See my motes on motors for more detail. The current needed to move the shaft in the coil is very low (less than 10 milliamps) so the coil can be energized by an output pin of our microcontroller. The current that can flow through the switch, however, is much higher. The lamp circuit is mostly separate from the microcontroller. A separate power source, with 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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