This is a common control voltage in industrial and telecommunications equipment, so the relays are common in surplus equipment. Many will actuate equally well on AC or DC, which makes them an easy solution when the control voltage is switched mechancially, as in the case of limit switches or magnetic reed switch sensors. Unfortunately, they`re not so simple to interface directly to microcontrollers as they
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require a separate supply and level shifting circuitry. Even so, one can easily control them with a separate supply and optoisolator. An optoisolator uses the illumination of a (mostly infared) LED to trigger a photosenitive resistor or transistor. This provides galvanic isolation between the control circuit and the device being switched, which also means that the power supplies don`t have to be the same voltage, or even share a common ground. Additionally, transistor-type optoisolators in DIP packages are extremely common and cheaply available if you don`t have a few in the parts bin. They also provide an easy method to control devices using a current loop. Using a current loop and a control current rather than a control voltage makes interfacing with a wide range of control voltages easy. I came across a few things that made this project possible and/or necessary. First, I had a large supply of 24V relays sitting around. Second, I had a few trays of Prem board-mount transformers with dual primaries (120/240 VAC operation) and dual secondaries that could be series-wired for 24 VAC output. Finally, I came across a bunch of 24V coil relays that could handle 5 Amps @ 125 VAC and came with sockets that could be board or panel mounted. I used one of them and a point-to-point controller in this relay-controlled receptacle project: The controller worked fine and could be driven by 3. 3/5/12 Volt control circuits without...
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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