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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Radio control for 15 teams, 433.92 MHz. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Radio control equipment

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The system is designed for radio control of 15 loads, at a frequency of 433,92 MHz at a short distance, if desired, transmitters of higher power can be used, thereby increasing the transmission range. It can be used in systems such as smart home, controlled home or car alarm, as well as remote control of high voltage loads. For example, you can build 1 receiver and two or more transmitters tuned to the same frequency, it is not necessary to use all 15 buttons in the transmitter, for example, only 5 buttons can be wired.

The design has a number of advantages

  1. small dimensions
  2. no SAW resonators
  3. stable operation due to the use of superheterodyne receiver
  4. ease of setup
  5. free firmware

The encoder and decoder board can be used with other types of receivers and transmitters. For a receiver on the MAX1473, the transmitter must radiate at 423,2 MHz.

Radio control for 15 teams, 433.92 MHz. circuit diagram
(click to enlarge)

The receiving part (Fig. 1) consists of (MAX1473 receiver + ATMEGA8 command decoder).

The decoder works in two modes

1) When you press button 1 on the encoder, load 1 is turned on, pressing it again will turn it off.

2) pressed button 1, load 1 turned on for half a second, then turned off. Mode switching is carried out by jumper J1, if there is no jumper J1, it works in mode No. 1, and when the jumper is set, then mode No. 2 works, but before that, the MK must be restarted.

Operating principle

The receiver is switched on according to a typical circuit, built on a MAX1473 chip, which is superheterodyne, can operate at frequencies of 315/433 MHz, in this circuit it is tuned to a frequency of 433,92 MHz. the local oscillator frequency is stabilized by quartz ZQ1 13,2256 MHz, in the microcircuit it is multiplied 32 times, F (local oscillator) = 13,2256x32 = 423,21 MHz. The frequency to which the receiver will be tuned \u423,21d F (local oscillator) + F (intermediate frequency) \u10,7d 433,92 + 2 \u1d ~ 1473 MHz, more precise tuning is carried out by selecting elements L1 and subscript capacitor C8. The RF signal received at the antenna is amplified and separated in the MAXXNUMX chip, a rectangular signal coming from the internal comparator is fed through the inverter (VTXNUMX) to the input of the command decoder (ATMEGAXNUMX), in which the transmitter command is decoded, then it switches the necessary loads.

The length of the antenna is approximately 3-10 cm.

A plastic screwdriver rotates the disk of capacitor C1.

Radio control for 15 teams, 433.92 MHz
(click to enlarge)

The transmitting part consists of (MAX1479 transmitter + ATMEGA8L command encoder) fig. 2. The command is sent by pressing the SB1-SB15 buttons, the additional SB16 button is used to turn off all loads, the SB17 button is used to turn on all loads, The signal encoded by the microcontroller is fed through the inverter (VT1) to the input of the MAX1479 transmitter, which outputs a high-frequency amplitude-pulse signal to the antenna .

The transmitter is built on a special MAX1479 microcircuit, a low-power transmitter capable of operating at a frequency of 300-450 MHz, with amplitude-pulse modulation, the generation frequency is set by quartz with a frequency of 13,560 MHz, which is multiplied 32 times in the microcircuit, F (transmitter) \u13,560d 32x433,92 \u8d 2.7 .5.5 MHz. The encoder is built on the ATMEGAXNUMXL MK, in the L version, the MK is powered by a low voltage of XNUMX-XNUMXV.

All buttons are enabled in a matrix system, the lines of which are connected to diodes VD1-5, through them a signal is sent to the input of an external interrupt PD2, which causes the microcontroller to wake up from the reduced power consumption mode (Power-down). From pin 32 DD1, a signal is received that allows the transmitter power amplifier to work. A chain with an HL1 LED indicates the generation of a signal by the encoder.

The second version (Fig. 3) of the transmitter, built on a special MAX1472 chip, differs mainly in the size of the package, SOT23-8, i.e. 8 pins, it is easier to solder than MAX1479.

The length of the antenna is approximately 5-15 cm, a variant with a dipole is possible. The transmitter does not need basic configuration and works immediately.

The output power of the MAX1479/MAX1472 transmitters is 10 mW or less.

The transmitters are powered within 2.5-3.8 V (power, respectively), for example, 1 tablet for 3, or even better, a battery from a mobile phone / player, at 3.6 V.

Radio control for 15 teams, 433.92 MHz
(click to enlarge)

Details of construction

The receiver and transmitter board can be made separately in the form of radio modules, decoders and power switches are also on separate boards. Mounting is mainly performed by surface mounting elements, resistors and capacitors in the 0805 package, transistors in the SOT-23 package.

The radio modules are mounted on a two-sided textolite glass, the lower foil serves as a common conductor, the connection to the upper layer is made through holes, by wiring.

The gap of the bottom foil from the edges of the board is somewhere around 1-3mm.

The transmitter board (1) must first be tinned with a thin layer of solder, the microcircuit must be precisely placed so that all the leads (4 sides) match, the MAX1479 is soldered with a blow dryer at a temperature of about 400 degrees, with a short supply of hot air, it is important not to fry! And follow the anti-static rules.

The MAX1472 chip can be soldered with a soldering iron with a thin tip, or also with a hair dryer.

Receiver coils - L1 is a half-turn wide 6mm and 6mm high, wire diameter 0.6-0.8mm,

L2 - in the form of a bracket 8 mm long, 4 mm high, wire diameter 0.6-0.8mm,

L3- 3 turns with a wire with a cross section of 0.2-0.35 mm, wind on a mandrel 2.5-3 mm, for example, on a rod from a pen or on a drill.

Transmitter coils L1 - 3 turns with a pitch of 1 mm with a wire with a cross section of 0.5-0.8 mm L2 4 turns with a diameter of 2.5-3 mm. It is desirable that the coils be made of silver-plated wire, you can use silver-plated terminals of C2-33 0.5-2W resistors, or the central core of a PK type cable.

In principle, the receiving module can be replaced with others designed to operate at a frequency of 433,92 MHz.

The encoder/decoder is mounted on a one-sided textolite glass. The transmitter and encoder board (5 commands) can be placed in a small-sized case in the form of a remote control, for example; G430A, housing for electronic equipment 90x50x16 mm.

Radio control for 15 teams, 433.92 MHz

On fig. 4 shows one of the options for power switches for switching high voltages. The distance between the modules should preferably be shorter, otherwise a shielding cable of the PK or MGTFE type should be used for the encoder/decoder signal wire. It is also possible to shield the entire receiver for reliable noise immunity.

Replacing parts

ATMEGA8(L) FQN32 microcontroller can be replaced by ATMEGA8(L) in DIP-28 package,

You just need to take into account that it has a different pinout (port / output), and adjust the printed circuit board.

Transistor KT817 (npn) on KT815, KT972.

Transistor BC847 (npn) on BC846 KT3130 (smd) or kt315 for conventional mounting.

Transistor BC857 (pnp) on BC856 KT3129 (smd) or kt361 for conventional mounting.

Diodes for keys KD522 on KD521. and other low-power, imported in smd package DL4148 or DL4448.

Radio control for 15 teams, 433.92 MHz

A ceramic intermediate frequency filter at 10,7 MHz, can be any suitable in size, for example, L10.7 MS, SFELF10M7FAA0, and if you're lucky, find it in the smd package SFECV10M7HA00-R0. It is important not to forget about its pinout Fig.5. Quartz resonators are desirable to be in the HC-49SM (smd) or HC-49S package, which will have to bend the leads.

Tact buttons can be, for example, TS-A2PS-130, or smd DTSM-32N, and their other varieties. Structural capacitors (smd) types TZB4Z030BA10 or TZC3Z030A110, TZV2Z030A11B00.

Relays of power keys, you can take any for any number of contacts, for a response voltage of 9-14V, it basically depends on what voltage should be turned on.

Domestic low-power; RES15-12V, RES49-12V, RES60-6V, more powerful than RES90-12V. imported 833H-1C-C-12VDC, relay 12V/7A, 250V.

The DA1 positive voltage stabilizer chip can be replaced with any stabilizer with an output voltage of + 5V, in any suitable package.

The circuit uses 78L05, in the SOT89 smd package, there is our analogue in the TO92 package KR1157EN502.

Chains marked with "*" at the beginning may not be installed.

Radio control for 15 teams, 433.92 MHz

Programming

Programming is carried out with a simple STK200/300 type programmer, connected directly to the encoder / decoder board, Fig. 6 after programming, the wires of the programmer are disconnected. It is recommended to program with 5,25 V supply voltage and compare the Flash memory with the written firmware file.

When programming, it is necessary to set and flash the FUSE switches as in Fig.7.

Radio control for 15 teams, 433.92 MHz

The Decoder_v1.hex file is loaded into the decoder microcontroller, the Coder_v1.hex file is loaded into the encoder microcontroller, for the first and second options.

The Coder_ns.hex file for the encoder does not contain a sleep mode, while it is possible to exclude the chain of diodes that are part of the matrix keyboard.

Radio control for 15 teams, 433.92 MHz. Photo of the finished device

Download firmware and printed circuit boards

Author: Knyazev I.S. (Knazev33), Knazevis_[dog]mail.ru, ICQ: 455864760; Publication: cxem.net

See other articles SectionRadio control equipment.

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Comments on the article:

Sashko Kozhanovsky
Cool scheme!!! [lol] But maybe someone knows how to reduce the turn-off hour to a minimum in the second version of the decoder? I want to use it to manage models of equipment.

a guest
Why in both circuits the "reset" leg of the atmega is not pulled up through a resistor to the power plus?


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