Radio control device (radio key) for 3 commands. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Radio control device (radio key) for 3 commands. 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 device *radio control for 3 commands or coded access device is designed to switch 3 different loads. The scope of such devices is very wide. It can be used to control garage doors, lighting, as a radio key for home or car alarms.

Small size allows you to place it in a case from a keychain or from a pager.

It should be noted that each pair of receiver-transmitter has its own individual code, i.e. the transmitter of the other pair will not be able to influence the "foreign" receiver in any way.

However, on an individual order, it is possible to manufacture (or flash) different combinations of the algorithm for operating devices like:

1. One transmitter controls multiple receivers.

2. Multiple transmitters control one or more receivers.

Transmitter

(click to enlarge)

It consists of an encoder and an RF generator with a power amplifier. Encoder - PIC 12 F 675. Encodes information about the pressed button and controls the master oscillator with a power amplifier. ZG and UM are standard circuit solutions that have proven themselves in work.

Receiver

(click to enlarge)

It consists of an RF part (RX 5000 microassembly) and a decoder. RX 5000 is an AM receiver with a sensitivity of at least 0,6 μV manufactured by RFM. It incorporates an active low-pass filter and a comparator (not used).

Decoder - PIC 12 F 675. Digitizes the incoming analog signal, decodes and executes commands.

The receiver has 2 modes of operation:

1. With fixation of commands (there is no jumper, a 10 kΩ resistor is soldered between 1 and 4 controller outputs - not in the photo), the LED remains on after the button is released until another command arrives.

2. Without fixing the commands (the jumper is soldered) The corresponding LED is on only while the button of its command is being held.

Controller Firmware

Demo (they are also debugging) versions of firmware are laid out for free use below.

What do they represent.

The transmitter - in the demo version becomes a generator with a frequency of 1,6 kHz (intermediate modulation frequency) immediately after power is applied to it.

Receiver - only the controller's internal comparator is involved in the demo version. The output of the comparator is programmatically connected to pin 5. On it, using the ULF, the transmitter signal is recorded to debug the device.

When tuning, you should achieve by selecting a 27 kΩ resistor (comparator response threshold), indicated on the diagram with an asterisk, for confident signal transmission from long distances and the absence of noise when the transmitter is turned off.

Download firmware

Features

Any AM and FM devices can be used as a receiver and transmitter (for example, a super-regenerator from a radio control system for 12 commands).

The device is also able to work via wires and infrared channel.

Due to the use of intermediate modulation, an increased noise immunity of the device was achieved.

Supply voltage 3 volts (but not more than 3,7)

Transmitter power - 5 mW. At the same time, the range of confident work with antennas 15 cm long is 100 m in open areas.

The frequency of the devices is 433,9 MHz.

Radio control device (radio key) for 3 commands. Photo of the finished device

Author: Sergey, Kremenchug, 8-050-942-35-95 or by mail: blaze @ vizit - net. com; Publication: cxem.net

See other articles Section Radio control equipment.

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