Radio control of three loads on RF modules. Scheme, description

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Radio control of three loads on "RF modules" using microcontrollers. 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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See also: RF - do-it-yourself modules

At present, the widespread use of digital technology, microcontrollers are confidently gaining a leading position in terms of the popularity of their use in structures for various purposes. Due to their high reliability and low cost, truly immense possibilities have opened up for many radio amateurs to implement their ideas with minimal costs for radio components.

The described radio control device is an example of accessibility for repetition even for beginners on their way into the fascinating world of amateur radio electronics. Despite its simplicity, it has sufficient noise immunity, thanks to a software-implemented system for confirming the control code, which leads to almost zero probability of false positives, unlike products of a similar nature from Sino-Deribasov "brands".

Described radio control unit for 3 independent loads allows you to control 3 electromagnetic relays at a distance of about 100 m in open areas. It is programmed to work in two modes depending on the position of the jumper on the receiver board.

The first algorithm of the device operation with fixing the command (the jumper is present).

This mode is designed to turn on the corresponding relay by pressing the button, and turn it off by pressing it again. This is true for all 3 teams. They work independently of each other. The commands generated by the transmitter controller have multiplicity. That is, a command to turn on is emitted once, and a second press is the turn off of the corresponding load.

The second mode of operation of the device (there is no jumper) provides for the closure of the corresponding relay only while the button is being held. Upon releasing it, the relay will turn off after 0,5 seconds. In this mode, the commands are also independent of each other.

Receiver

The heart of the receiver is the incoming command decoder based on the popular 12F675 controller.

As the radio frequency part, a super-regenerator assembled on a BFP67 transistor was used. If the elements indicated in the diagram are used during assembly, its adjustment consists only in pushing the turns of the loop coil to get the receiver into the frequency band emitted by the transmitter. During the tuning period, it is convenient to control the signal from pin 1 of the LM358 (output of the first op-amp of the microcircuit). It is worth emphasizing that one should not expect a lot of noise from the receiver in the absence of a signal (an indicator of the performance of most super-regenerators). This receiver, having a sensitivity of about 1 μV, practically does not make noise. To put it more precisely, it makes noise at a higher frequency than is usually accepted in this type of circuit design.

After the first low-frequency amplifier, the signal is fed to the comparator, from where it is already in digital form to the controller input.

In the photo, the contour coil of the receiver is flooded with zapon varnish, which inevitably leads to the tuning of the superregenerator down by several MHz. It is necessary, while the varnish is liquid, to slightly push the turns of the coil and periodically monitor the transmitter signal from pin 1 of the LM358 until it dries completely.

(click to enlarge)

Transmitter

It consists of an encoder made on a 12F675 controller and an RF part.

The encoder polls the buttons, generates a code sequence, and controls the RF part. The RF part consists of a generator and a power amplifier. The scheme is standard. Provided that the details indicated in the diagram are used, it works immediately and does not need to be configured.

The actual high-frequency parts are taken from "RF - do-it-yourself modules"with minor changes due to the use of a different type of transistors in the transmitter. The receiving RF module is "merged" into one board with a command decoder.

Antennas and receiver and transmitter quarter-wave pieces of wire 16 cm long.

Demo version of the firmware can be downloaded from the link below. "Demo" consists of a limited time use of both the receiver and the transmitter.

That is, after some time of operation, the executive part stops responding to commands (it is necessary to re-flash the controller).

(click to enlarge)

Download board layout files in lay format and demo firmware version in HEX format

Radio control of three loads on "RF modules" using microcontrollers. Radio control of three loads on "RF modules" using microcontrollers. Receiver photo

Radio control of three loads on "RF modules" using microcontrollers. Radio control of three loads on "RF modules" using microcontrollers. Transmitter photo

Radio control of three loads on "RF modules" using microcontrollers. Radio control of three loads on "RF modules" using microcontrollers

Author: Sergey, Kremenchuk, 8-050-942-35-95, blaze@vizit-net.com, blaze2006@ukr.net; Publication: cxem.net

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