High-current electronic key with touch control. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

High-current electronic key with touch control. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

Comments on the article

This design is intended for switching various devices that consume high current (up to 30 ... 40 A) and are powered by a DC source with a voltage of fractions of a volt. The basis of the key is a powerful field-effect switching transistor IRLR2905 or similar (see the reference sheet "Powerful field-effect switching transistors from International Rectifier" in Radio, 2001, No. 5, p. 45). The resistance of its open channel does not exceed 0,027 Ohm, and to control (open) it is enough to apply a voltage of more than 2 V to the gate.

If the supply voltage is less than 5 V, a device variant should be used, the circuit of which is shown in fig. 1. It works like this. When touching the sensor element E1, the pickup voltage through the capacitor C1 is supplied to the rectifier assembled on the zener diode VD1. The negative half-wave is closed to a common wire through a zener diode, and the positive one is limited by it and passes through the resistor R2 to the gate of the transistor VT1. Capacitor C3 smooths out the ripple of the rectified voltage. A positive gate voltage turns on the transistor and current flows through the RH load.

High current electronic key with touch control

The key can operate at a supply voltage of up to 55 V and switch a load that consumes the maximum current determined by the transistor used (40 A in our case). If the load resistance is inductive in nature, then it is desirable to introduce a VD2 diode into the device.

If the supply voltage is more than 5V, it can be used to drive the transistor. In this case, the sensor element is made of two plates - E1 and E2 (Fig. 2), and its resistance changes when both of them are touched. In the initial state, the resistance between the plates is high, the voltage at the gate of the transistor is close to zero, so it is closed. When you touch the finger plates, the resistance between them decreases, there will be a constant voltage at the gate of the transistor and it will open.

High current electronic key with touch control

Diode VD2 and zener diode VD1 protect the transistor from pickups and charges of static electricity, and the zener diode also limits the maximum value of the constant voltage at the gate. As in the first option, the key will be open as long as the touch element is touched.

The device can use any transistor, highlighted in color in the table above the mentioned reference sheet. In this case, of course, the maximum current switched by the timer will be determined by the type of transistor used. Capacitors - K10 - 17, KLS, resistors - MLT, C2 - 33, P1 - 4, P1 - 12. Zener diode - any low-power small-sized stabilization voltage of 5,1 ... 10 V with a low minimum stabilization current. For a low-power inductive load, the VD2 diode in fig. 1 - KD102, KD103, KD105 with any letter index, and for powerful - KD109A - KD109V, KD212A, KD212B or similar.

For the first version of the device, the sensor element can be made in the form of a small contact pad. For the second option, it can be made in the form of a plate of one-sided foil fiberglass with two conductive pads and a gap between them of 1 ... 2 mm.

If the load current is significant, the connecting wires must be of the appropriate section.

Author: I. Nechaev, Kursk

See other articles Section Beginner radio amateur.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Traffic noise delays the growth of chicks 06.05.2024

The sounds that surround us in modern cities are becoming increasingly piercing. However, few people think about how this noise affects the animal world, especially such delicate creatures as chicks that have not yet hatched from their eggs. Recent research is shedding light on this issue, indicating serious consequences for their development and survival. Scientists have found that exposure of zebra diamondback chicks to traffic noise can cause serious disruption to their development. Experiments have shown that noise pollution can significantly delay their hatching, and those chicks that do emerge face a number of health-promoting problems. The researchers also found that the negative effects of noise pollution extend into the adult birds. Reduced chances of reproduction and decreased fertility indicate the long-term effects that traffic noise has on wildlife. The study results highlight the need ... >>

Wireless speaker Samsung Music Frame HW-LS60D 06.05.2024

In the world of modern audio technology, manufacturers strive not only for impeccable sound quality, but also for combining functionality with aesthetics. One of the latest innovative steps in this direction is the new Samsung Music Frame HW-LS60D wireless speaker system, presented at the 2024 World of Samsung event. The Samsung HW-LS60D is more than just a speaker system, it's the art of frame-style sound. The combination of a 6-speaker system with Dolby Atmos support and a stylish photo frame design makes this product the perfect addition to any interior. The new Samsung Music Frame features advanced technologies including Adaptive Audio that delivers clear dialogue at any volume level, and automatic room optimization for rich audio reproduction. With support for Spotify, Tidal Hi-Fi and Bluetooth 5.2 connections, as well as smart assistant integration, this speaker is ready to satisfy your ... >>

A New Way to Control and Manipulate Optical Signals 05.05.2024

The modern world of science and technology is developing rapidly, and every day new methods and technologies appear that open up new prospects for us in various fields. One such innovation is the development by German scientists of a new way to control optical signals, which could lead to significant progress in the field of photonics. Recent research has allowed German scientists to create a tunable waveplate inside a fused silica waveguide. This method, based on the use of a liquid crystal layer, allows one to effectively change the polarization of light passing through a waveguide. This technological breakthrough opens up new prospects for the development of compact and efficient photonic devices capable of processing large volumes of data. The electro-optical control of polarization provided by the new method could provide the basis for a new class of integrated photonic devices. This opens up great opportunities for ... >>

Random news from the Archive

Turbine from the other side of the world 01.07.2004

In 2009, the Three Gorges power plant on the Yangtze River (China) is to be put into operation.

The reservoir, the creation of which had to relocate almost two million people from 13 cities, 116 towns and about 4500 villages, is larger in area than Switzerland. For the first stage of the power plant, eight turbines were ordered in France, three of them will be delivered from there, and five were built by French specialists at a plant in China.

The first of three turbines has just arrived on site. The turbine plant is located in Grenoble, and the cargo was supposed to be sent from the port of Marseille. However, since not all bridges on the road from Grenoble to Marseille could withstand a load with a diameter of 11 meters and a weight of 450 tons, the turbine was delivered to Marseille in parts and assembled there. For this, an assembly shop was built on the shores of the Mediterranean Sea.

Having sailed 20 kilometers on a ship to Shanghai, the turbine was loaded onto a barge and followed the river almost to the very dam. The last 30 kilometers had to be overcome by land, on a cargo platform with 288 wheels.

Other interesting news:

▪ Heat resistant bioplastic

▪ Protein nanomachines from bacteria

▪ New series of PMEG Schottky diodes

▪ Cost-Effective Wi-Fi Chips for Consumer Electronics

▪ The perfect snack for heart health

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Signal limiters, compressors. Article selection

▪ article Workers of the sea. Popular expression

▪ article Who made the first table? Detailed answer

▪ article Hawthorn smoothed. Legends, cultivation, methods of application

▪ article Modernization of the electric drill. Encyclopedia of radio electronics and electrical engineering

▪ article Automatic power switching. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews