Analog radio control system. Scheme, description

Free technical library

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

Analog radio control system. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Radio control

Comments on the article

To control ship models at a distance of up to 150-200 meters, simple analog systems are usually used, built on the principle of frequency coding of commands. The transmitter of such a system is built according to the scheme of a high-frequency generator, the frequency of which is determined by the LC circuit without the use of a quartz resonator ("self-fornication"). Modulation is carried out using a multivibrator, the frequency of which is changed either by connecting different resistors or capacitors, or smoothly using a variable resistor, on the handle of which there are marks that make it possible to set frequencies that specify different commands. The receiver of such a system is built according to the super-regenerator circuit with a set of low-frequency LC circuits and transistor detector switches at the output.

Such a scheme has been used for more than a dozen years, and it can rightfully be called a classic. Its main advantage is its relative simplicity. At the same time, there are significant drawbacks: instability of the super-regenerative receiving path, the need to use scarce low-frequency ferrite cores and wind multi-turn coils for the decoder on them. The transition to a digital coding method is certainly progressive, but the need to transmit and receive a clear pulse sequence, in which each modulating pulse is taken into account, leads to malfunctions during control in conditions of interference from propulsion motors and other actuators. Therefore, it is necessary to greatly complicate the circuits of digital encoders and decoders.

This article describes a modern version of an analog three-command radio control system with frequency coding. Compared to the classic, there are many differences. The frequency channel has been moved to the VHF-FM broadcasting range (a section free from broadcasting stations is selected), frequency modulation. The modulating multivibrator is built on a digital MOS chip (K176LE5). The receiving path is made according to a superheterodyne circuit with a low IF on a specialized microcircuit designed to build the receiving path of a VHF FM broadcasting receiver (KXA058 microassembly). The low-frequency filters of the receiving path decoder are made according to active circuits on operational amplifiers without the use of LC circuits. As a result, the transition to a higher frequency range and the use of frequency modulation increases the noise immunity of the entire system. The higher sensitivity of the superheterodyne receiving path, in comparison with the superregenerator, makes it possible to reduce the output power of the transmitter, which, together with the low consumption of the master oscillator built on the K176 microcircuit, increases the service life of the transmitter's galvanic batteries. The implementation of the decoder on active RC filters and operational amplifiers does not require complex winding work.

The schematic diagram of the transmitter is shown in Figure 1.

Analog radio control system
Fig. 1

The transmitter itself is built according to the LC circuit of a high-frequency generator based on a transistor VT1 with a voltage boost circuit R1 C5. The peculiarity of such a circuit is that the maximum output radiation power, with the correct selection of the ratio of resistors R2 and R3, is combined with the minimum current consumption of the transistor. For each instance of the GT311I (or Zh) transistor, you need to select the values of these resistors in such a way as to obtain maximum high-frequency radiation, and at the same time, the generator current consumption should decrease.

The modulating target consists of a VD1 varicap and a capacitor C6 connected in series with it. FM is produced in the emitter circuit VT1.

The source of modulating pulses is a multivibrator on a D1 chip. Variable resistor R8 sets the frequency corresponding to the desired command, and then press the button S1. The multivibrator will generate pulses as long as this button is pressed. The pulses are fed to the varicap and modulate the RF radiation.

The scheme of the receiver with a decoder is shown in Figure 2.

Rice. 2 (click to enlarge)

The receiving path is made on a hybrid chip A1 - KXA058, which is the receiving path of a VHF-FM broadcasting receiver. The tuning frequency depends on the tuning frequency of the heterodyne circuit L1 C3. The low-frequency signal is taken from pin 15 A1 and fed to the inputs of three active filters on operational amplifiers A2-A4. The filter on A2 is set to 390Hz which corresponds to the first command, the filter on A3 is set to 820Hz which corresponds to the second command, and the last filter on A4 is set to 1100Hz which is the third command.

The voltage divider R15-R16-R17 is used to set the bias voltage equal to half the supply voltage for supply to the direct inputs A2-A4, so that these operational amplifiers can operate with a single supply.

At the outputs of the filters, transistor keys-detectors are connected, which control electromagnetic relays, the contacts of which are not shown in the diagram. The power of these relays depends on the particular application of the radio control system.

If the first command is transmitted, the AC voltage is amplified by the operational amplifier A2 to a level sufficient to open the transistor VT1. It begins to open periodically, charging capacitor C20 with collector current pulses. As it charges, the voltage on it increases, and at a certain level, the transistor VT2 opens. As a result, relay P1 is activated, and its contacts (not shown in the diagram) turn on the actuator, which should be triggered when the first command is given.

At this time, the other two relays are de-energized because the frequency of the modulating signal lies outside their resonant bands, and amplifiers A3 and A4 do not amplify the signal.

Similarly, relays P2 and P3 are turned on when the other two commands are given.

The receiver and transmitter coils are frameless; for their winding, a temporary mandrel with a diameter of 4 mm is used (drill shank with a diameter of 4 mm). Winding is carried out with a PEV 0,3-0,5 wire. The coil is wound on the drill shank, then its leads are formed, cleaned and tinned. After that, the resulting "spring" is removed from the drill and installed on the board. The coils are the same, for the range of 64-75 MHz they contain 12 turns each, for the range of 88-108 MHz - 7 turns each. Electromagnetic relays are used small-sized type RES-55A for a response voltage of 6-10V. You can use the relay RES-47, RES-43, RES-10, RES-15 with a winding for a voltage of 6-10V. The role of the receiver antenna is performed by a wire pin about 50 cm long, as the transmitter antenna, a telescopic antenna 75 cm long from a transistor receiver or radio tape recorder is used.

Operational amplifiers K140UD6 can be replaced by 140UD6. K140UD7, 140UD7, K140UD608, K140UD708.

The GT311I transistor can be replaced with a GT311Zh; during installation, the output of the transistor case must be connected to the power minus. KT315 transistors can be replaced with any of the KT315, KT3102, KT342, KT316 series. KT814 transistors - for any of the KT814, KT816 series.

Ceramic tuning capacitors, type KPK-1M. Permanent capacitors operating in high-frequency circuits such as KT or KD. or similar imported ones with a minimum TKE. Capacitors operating in low-frequency filters of the K10-7, KPS, KM or similar decoder. Electrolytic capacitors - K50-35 or imported.

In the absence of a KXA058 chip, the receiving path can be assembled on K174XA34, K174XA42 or K1066XA1 microcircuits according to typical schemes that have been repeatedly described in the literature.

Tuning should begin with the receiving path. By connecting the input of any UZCH to the output of the A1 microcircuit (to pin 15), by rotating the rotor C3, tune the receiver to any VHF station (this way you can check its operation). Then, guided by the scale of the factory receiver, tune the receiving path to the part of the range where there are no radio stations.

Then turn on the transmitter, close S1 and by rotating the rotor C1 (Figure 1) adjust the transmitter so that its signal can be heard from the speaker of the control amplifier. Further, by selecting the ratings of R2 and R3 (and slightly adjusting C1), set the VT1 operation mode (Figure 1), which will provide the maximum communication range between the receiver and transmitter.

Next, disconnect the amplifier from the output of the receiver, and while observing the electromagnetic relays, turn the variable resistor R8 of the transmitter, keeping the S1 button closed. Make three visible marks on the R8 knob corresponding to the relay being turned on. If necessary, you can choose the value R7 or C8 (Figure 1).

The range of the system when controlling a ship model is about 150 meters in the line of sight.

Author: R. Lyzhin

See other articles Section Radio control.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

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 ... >>

Primium Seneca keyboard 05.05.2024

Keyboards are an integral part of our daily computer work. However, one of the main problems that users face is noise, especially in the case of premium models. But with the new Seneca keyboard from Norbauer & Co, that may change. Seneca is not just a keyboard, it is the result of five years of development work to create the ideal device. Every aspect of this keyboard, from acoustic properties to mechanical characteristics, has been carefully considered and balanced. One of the key features of Seneca is its silent stabilizers, which solve the noise problem common to many keyboards. In addition, the keyboard supports various key widths, making it convenient for any user. Although Seneca is not yet available for purchase, it is scheduled for release in late summer. Norbauer & Co's Seneca represents new standards in keyboard design. Her ... >>

The world's tallest astronomical observatory opened 04.05.2024

Exploring space and its mysteries is a task that attracts the attention of astronomers from all over the world. In the fresh air of the high mountains, far from city light pollution, the stars and planets reveal their secrets with greater clarity. A new page is opening in the history of astronomy with the opening of the world's highest astronomical observatory - the Atacama Observatory of the University of Tokyo. The Atacama Observatory, located at an altitude of 5640 meters above sea level, opens up new opportunities for astronomers in the study of space. This site has become the highest location for a ground-based telescope, providing researchers with a unique tool for studying infrared waves in the Universe. Although the high altitude location provides clearer skies and less interference from the atmosphere, building an observatory on a high mountain poses enormous difficulties and challenges. However, despite the difficulties, the new observatory opens up broad research prospects for astronomers. ... >>

Random news from the Archive

Ultrasonic Microphone Jamming Wristband 24.02.2020

Researchers at the University of Chicago have created an experimental bracelet that uses 24 speakers to generate ultrasonic noise to suppress most microphones, regardless of their directionality.

The gadget uses the non-linear distortions of the built-in amplifier to "leak" ultrasonic noise into the audio range, thus excluding the possibility of recording the conversation.

Such an unusual design of the bracelet is by no means a tribute to fashion. It not only generates omnidirectional interference, but also eliminates blind spots (when sensors cancel each other) when moving the wrist. As a result, the bracelet is even more effective than specialized stationary jammers and can even suppress hidden microphones.

Ultrasound is imperceptible to others, except perhaps young people and dogs, but all nearby microphones will only detect high frequency noise instead of other sounds.

Such a gadget can be useful for owners of smart devices, since smart speakers, calls, and the like have a microphone almost always on. According to statistics, one in five American adults owns a smart speaker, and recordings of conversations "overheard" and recorded by smart devices have repeatedly appeared on the Web.

Other interesting news:

▪ The length of the day on Venus is constantly different

▪ Logs in glass

▪ digital tombstone

▪ Updated Efinix Titanium FPGA line

▪ Smart speakers help save lives

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Voltage stabilizers. Article selection

▪ article Illusions due to structural features of the eye. Encyclopedia of visual illusions

▪ article How was glass discovered? Detailed answer

▪ article Preparer of padding and flooring materials, engaged in cutting upholstery fabrics. Standard instruction on labor protection

▪ article Nickel plating of copper, iron and steel. Simple recipes and tips

▪ article Current switch KR1055KT1A. 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