DIY radio control. The simplest single-command radio control circuit for models (3 transistors) How to make a radio control

Many people wanted to assemble a simple radio control circuit, but one that would be multifunctional and for a fairly long distance. I finally put together this circuit, spending almost a month on it. I drew the tracks on the boards by hand, since the printer does not print such thin ones. In the photo of the receiver there are LEDs with uncut leads - I soldered them only to demonstrate the operation of the radio control. In the future I will unsolder them and assemble a radio-controlled airplane.

The radio control equipment circuit consists of only two microcircuits: the MRF49XA transceiver and the PIC16F628A microcontroller. The parts are basically available, but for me the problem was the transceiver, I had to order it online. and download the payment here. More details about the device:

MRF49XA is a small-sized transceiver that has the ability to operate in three frequency ranges.
- Low frequency range: 430.24 - 439.75 MHz (2.5 kHz step).
- High frequency range A: 860.48 - 879.51 MHz (5 kHz step).
- High frequency range B: 900.72 - 929.27 MHz (7.5 kHz step).
The range limits are indicated subject to the use of a reference quartz with a frequency of 10 MHz.

Schematic diagram of the transmitter:

The TX circuit has quite a few parts. And it is very stable, moreover, it does not even require configuration, it works immediately after assembly. The distance (according to the source) is about 200 meters.

Now to the receiver. The RX block is made according to a similar scheme, the only differences are in the LEDs, firmware and buttons. Parameters of the 10 command radio control unit:

Transmitter:
Power - 10 mW
Supply voltage 2.2 - 3.8 V (according to the datasheet for m/s, in practice it works normally up to 5 volts).
The current consumed in transmission mode is 25 mA.
Quiescent current - 25 µA.
Data speed - 1kbit/sec.
An integer number of data packets are always transmitted.
Modulation - FSK.
Noise-resistant coding, checksum transmission.

Receiver:
Sensitivity - 0.7 µV.
Supply voltage 2.2 - 3.8 V (according to the datasheet for the microcircuit, in practice it works normally up to 5 volts).
Constant current consumption - 12 mA.
Data speed up to 2 kbit/sec. Limited by software.
Modulation - FSK.
Noise-resistant coding, checksum calculation upon reception.

Advantages of this scheme

The ability to press any combination of any number of transmitter buttons at the same time. The receiver will display the pressed buttons in real mode with LEDs. Simply put, while a button (or combination of buttons) on the transmitting part is pressed, the corresponding LED (or combination of LEDs) on the receiving part is lit.

When power is supplied to the receiver and transmitter, they go into test mode for 3 seconds. At this time nothing works, after 3 seconds both circuits are ready for operation.

The button (or combination of buttons) is released - the corresponding LEDs immediately go out. Ideal for radio control of various toys - boats, planes, cars. Or it can be used as a remote control unit for various actuators in production.

On the transmitter circuit board, the buttons are located in one row, but I decided to assemble something like a remote control on a separate board.

Both modules are powered by 3.7V batteries. The receiver, which consumes noticeably less current, has a battery from an electronic cigarette, the transmitter - from my favorite phone)) I assembled and tested the circuit found on the VRTP website: [)eNiS

Discuss the article RADIO CONTROL ON A MICROCONTROLLER

In some cases, a single-command remote control system is required, which is quite simple, cheap, and has a good range. For example, in rocket simulation, when at a certain moment you need to throw out a parachute. Typically, for such purposes, a system consisting of a simple super-regenerative receiver and transmitter is used. Of course, such a circuit is very simple in terms of the number of transistors, but to obtain good sensitivity, the super-regenerator receiver needs painstaking tuning and adjustment, which is also easily confused under the influence of such external factors as the influence of external capacitors, changes in temperature, and humidity. And the problem is not only in the deviation of the tuning frequency (this is not so scary), but in the fact that the feedback coefficient in the super-regenerator, the transistor mode, changes, which ultimately turns the super-regenerative receiver into a regular detector receiver or into a generator.

More stable parameters with the same simplicity (in terms of the number of parts) can be achieved if the receiving path is built using a superheterodyne circuit on an integrated circuit. But specialized microcircuits for communication equipment are not always available. But surely every radio amateur will have a K174XA34 microcircuit or even a ready-made broadcast receiving path based on it. Some time ago there was a craze for designing VHF-FM broadcast receivers based on it. Now many of them have been sent “to the distant shelf.”

Let me remind you that the K174XA34 microcircuit (analogue of TDA7021) is a superheterodyne radio receiving path of the VHF-FM range, operating at a low intermediate frequency (70 kHz). Such a low IF allows, in the simplest version, to limit ourselves to just one circuit - a heterodyne circuit. Get rid of LC or piezoceramic IF filters (the filters are made using op-amps using RC circuits). And the result is a receiving path that requires almost no adjustment - if everything is soldered correctly, it works right away - just adjust the local oscillator circuit and you're done.

K174XA34 microcircuits were produced in 16 and 18-pin packages. Interestingly, their pinouts are almost the same. They can even be plugged into the same board by bending or cutting off the extra leads, or leaving two holes empty. You just need to mentally imagine that the 18-pin case does not have pins 9 and 10. If you do not take them into account, then the numbers are the same as for the 16-pin version. I had a chip in a 16-pin package.

And so, the 16-pin version has pin 9 (the same as pin 11 for the 18-pin version), so this pin was usually either not used or served as a fine-tuning indicator. The voltage on it varies depending on the magnitude of the input signal. So, if this voltage is applied from it to a transistor switch with an electromagnetic relay at the output, then when the transmitter is turned on (even without modulation), the relay will switch contacts.

In practice, we take a typical receiving path on the K174XA34 and use the 9th pin (Fig. 1). Now all that remains is to tune the receiving path to the desired frequency using the L1-C2 circuit. And adjust the relay response threshold with resistor R2.
The receiver antenna can be of any design, depending on the location where the receiving path will be installed. My antenna is a rigid steel wire 30 cm long.
Transmitter circuit shown in Figure 2. This is a single-stage RF generator with an antenna at the output.

The transmitter must be configured with the antenna connected. A wire rod at least 1 meter long can be used as an antenna. During the setup process, you need to tune the transmitter to a free frequency in the VHF-FM range. To do this, you need a control VHF-FM receiver with a fine-tuning indicator. The transmitter operates without modulation, so the fact of reception will be visible only by the fine tuning indicator. However, you can temporarily make modulation by applying some kind of audio signal to the base of transistor VT1 (Fig. 2.).

Setting the transmitter frequency with coil L1. The depth of the PIC can be changed by changing the ratio of capacitors C2 and SZ (it will be more convenient if you replace them with trimmers). Then you will need to fine-tune the frequency again.
The operating mode of the cascade is set experimentally by resistor R1 according to the best output, but the current consumption should not be more than 50 mA.

Details. The local oscillator coil of the receiving path is frameless. Its internal diameter is 3 mm. The wire is PEV 0.43, and the number of turns is 12. You can change the inductance of the coil by compressing and stretching it like a spring.
The transmitter coil has a similar design and its inductance is also regulated. But the internal diameter of the coil is 5 mm, and the number of turns is 8. The wire is also thicker - PEV 0.61.
In general, these coils can be wound with almost any winding or silver-plated wire with a cross-section from 0.3 to 1.0 mm.

Low-power electromagnetic relay with a 5V winding (RES-55A, winding resistance 100 Ohm). You can use another relay with a 5V winding. If you need to work with a relay with a winding at a higher voltage, you need to increase the supply voltage of the circuit accordingly, and connect a 4.5-5.5V zener diode in parallel with capacitor C14.

What I would like to say on my own is that it is an excellent solution in any remote control situation. First of all, this applies to situations where there is a need to manage a large number of devices at a distance. Even if you don’t need to control a large number of loads at a distance, it’s worth doing the development, since the design is not complicated! A couple of not rare components are a microcontroller PIC16F628A and microcircuit MRF49XA - transceiver

A wonderful development has been languishing on the Internet for a long time and is gaining positive reviews. It was named in honor of its creator (10 command radio control on mrf49xa from blaze) and is located at -

Below is the article:

Transmitter circuit:

Consists of a control controller and a transceiver MRF49XA.

Receiver circuit:

The receiver circuit consists of the same elements as the transmitter. In practice, the difference between the receiver and the transmitter (not taking into account the LEDs and buttons) consists only in the software part.

A little about microcircuits:

MRF49XA- a small-sized transceiver that has the ability to operate in three frequency ranges.
1. Low frequency range: 430.24 - 439.75 MHz(2.5 kHz step).
2. High frequency range A: 860.48 - 879.51 MHz(5 kHz step).
3. High frequency range B: 900.72 - 929.27 MHz(7.5 kHz step).

The range limits are indicated subject to the use of a reference quartz with a frequency of 10 MHz, provided by the manufacturer. With 11 MHz reference crystals, the devices operated normally at 481 MHz. Detailed studies on the topic of the maximum “tightening” of the frequency relative to that declared by the manufacturer have not been carried out. Presumably, it may not be as wide as in the TXC101 chip, since in the datasheet MRF49XA Mention is made of reduced phase noise, one way to achieve which is to narrow the tuning range of the VCO.

The devices have the following technical characteristics:
Transmitter.
Power - 10 mW.

The current consumed in transmission mode is 25 mA.
Quiescent current - 25 µA.
Data speed - 1kbit/sec.
An integer number of data packets are always transmitted.
FSK modulation.
Noise-resistant coding, checksum transmission.

Receiver.
Sensitivity - 0.7 µV.
Supply voltage - 2.2 - 3.8 V (according to the datasheet for ms, in practice it works normally up to 5 volts).
Constant current consumption - 12 mA.
Data speed up to 2 kbit/sec. Limited by software.
FSK modulation.
Noise-resistant coding, checksum calculation upon reception.
Work algorithm.
The ability to press any combination of any number of transmitter buttons at the same time. The receiver will display the pressed buttons in real mode with LEDs. Simply put, while a button (or combination of buttons) on the transmitting part is pressed, the corresponding LED (or combination of LEDs) on the receiving part is lit.
When a button (or combination of buttons) is released, the corresponding LEDs immediately go out.
Test mode.
Both the receiver and the transmitter, upon supplying power to them, enter test mode for 3 seconds. Both the receiver and the transmitter are switched on to transmit the carrier frequency programmed in the EEPROM for 1 second 2 times with a pause of 1 second (during the pause the transmission is turned off). This is convenient when programming devices. Next, both devices are ready for use.

Controller programming.
EEPROM of the transmitter controller.


The top line of EEPROM after flashing and supplying power to the transmitter controller will look like this...

80 1F - (4xx MHz subband) - Config RG
AC 80 - (exact frequency value 438 MHz) - Freg Setting RG
98 F0 - (maximum transmitter power, deviation 240 kHz) - Tx Config RG

82 39 - (transmitter on) - Pow Management RG.

The first memory cell of the second row (address 10 h) — identifier. Default here FF. The identifier can be anything within a byte (0 ... FF). This is the individual number (code) of the remote control. At the same address in the memory of the receiver controller is its identifier. They must match. This makes it possible to create different receiver/transmitter pairs.

Receiver controller EEPROM.
All EEPROM settings mentioned below will be written automatically into place as soon as power is supplied to the controller after its firmware is updated.
The data in each cell can be changed at your discretion. If you enter FF into any cell used for data (except ID), the next time the power is turned on, this cell will immediately be overwritten with default data.

The top line of EEPROM after flashing the firmware and supplying power to the receiver controller will look like this...

80 1F - (4xx MHz subband) - Config RG

AC 80 - (exact frequency value 438 MHz) - Freg Setting RG
91 20 — (receiver bandwidth 400 kHz, maximum sensitivity) — Rx Config RG
C6 94 - (data speed - no faster than 2 kbit/sec) - Data Rate RG
C4 00 - (AFC disabled) - AFG RG
82 D9 - (receiver on) - Pow Management RG.
The first memory cell of the second row (address 10 h) — receiver identifier.
To correctly change the contents of registers of both the receiver and transmitter, use the program RFICDA by selecting the chip TRC102 (this is a clone of MRF49XA).
Notes
The reverse side of the boards is a solid mass (tinned foil).
The range of reliable operation in line of sight conditions is 200 m.
The number of turns of the receiver and transmitter coils is 6. If you use an 11 MHz reference crystal instead of 10 MHz, the frequency will “go” higher than about 40 MHz. Maximum power and sensitivity in this case will be with 5 turns of the receiver and transmitter circuits.

My implementation

At the time of implementation of the device, I had a wonderful camera at hand, so the process of making a board and installing parts on the board turned out to be more exciting than ever. And this is what it led to:

The first step is to make a printed circuit board. To do this, I tried to dwell in as much detail as possible on the process of its manufacture.

We cut out the required size of the board. We see that there are oxides - we need to get rid of them. The thickness was 1.5 mm.

The next stage is cleaning the surface; for this you should select the necessary equipment, namely:

1. Acetone;

2. Sandpaper (zero grade);

3. Eraser

4. Means for cleaning rosin, flux, oxides.

Acetone and means for washing and cleaning contacts from oxides and experimental board

The cleaning process occurs as shown in the photo:

Using sandpaper we clean the surface of the fiberglass laminate. Since it is double-sided, we do everything on both sides.

We take acetone and degrease the surface + wash off the remaining sandpaper crumbs.

And veil - a clean board, you can apply a signet using the laser-iron method. But for this you need a signet :)

Cutting out from the total amount Trimming off the excess

We take the cut out seals of the receiver and transmitter and apply them to the fiberglass as follows:

Type of signet on fiberglass

Turning it over

We take the iron and heat the whole thing evenly until a trace appears on the back side. IMPORTANT NOT TO OVERHEAT!Otherwise the toner will float! Hold for 30-40 seconds. We evenly stroke the difficult and poorly heated areas of the signet. The result of a good transfer of toner to fiberglass is the appearance of an imprint of tracks.

Smooth and weighty base of the iron Apply a heated iron to the signet
We press the signet and translate.

This is what the finished printed sign looks like on the second side of glossy magazine paper. The tracks should be visible approximately as in the photo:

We perform a similar process with the second signet, which in your case can be either a receiver or a transmitter. I placed everything on one piece of fiberglass

Everything should cool down. Then carefully remove the paper with your finger under running water. Roll it with your fingers using slightly warm water.

Under slightly warm water Roll up the paper with your fingers Cleaning result

Not all paper can be removed this way. When the board dries, a white “patina” remains, which, when etched, can create some unetched areas between the tracks. The distance is small.

Therefore, we take thin tweezers or a gypsy needle and remove the excess. The photo shows it great!

In addition to the remains of paper, the photo shows how, as a result of overheating, the contact pads for the microcircuit have stuck together in some places. They need to be carefully separated, using the same needle, as carefully as possible (scraping off part of the toner) between the contact pads.

When everything is ready, we move on to the next stage - etching.

Since we have double-sided fiberglass and the reverse side is a solid mass, we need to keep the copper foil there. For this purpose, we will seal it with tape.

Adhesive tape and protected board The second side is protected from etching by a layer of adhesive tape Electrical tape as a “handle” for easy etching of the board

Now we etch the board. I do this the old fashioned way. I dilute 1 part ferric chloride to 3 parts water. All the solution is in the jar. Convenient to store and use. I heat it up in the microwave.

Each board was etched separately. Now we take the already familiar “zero” in our hands and clean the toner on the board

Hello everyone, three months ago - while sitting “on the answers of mail ru” I came across a question: http://otvet.mail.ru/question/92397727, after the answer I gave, the author of the question began to write to me in a personal message, from the correspondence it became known that Comrade “Ivan Ruzhitsky”, also known as “STAWR”, builds a remote control car whenever possible without “expensive” factory hardware.

From what he purchased, he had RF modules at 433 MHz and a “bucket” of radio components.

I wasn’t exactly “sick” with this idea, but I still began to think about the possibility of implementing this project from the technical side.
At that time, I was already quite well versed in the theory of radio control (I think so), in addition; some developments were already in service.

Well, for people who are interested - the Administration came up with a button......

So:
All the nodes were made “on the knee”, so there is no “beauty”, the main task is to find out how feasible this project is and how much it will “come out” in rubles and in labor.

REMOTE CONTROLLER:
I didn’t make a homemade transmitter for two reasons:
1. Ivan already has it.
2. Once I tried to stir up 27 MHz - nothing good came of it.
Since the control was designed to be proportional, all sorts of remote controls from Chinese rubbish disappeared by themselves.

I took the encoder circuit (channel encoder) from this site: http://ivan.bmstu.ru/avia_site/r_main/HWR/TX/CODERS/3/index.html
Thank you very much to the authors, it was because of this device that I had to learn how to “flash” the MK.
I bought the transmitter and receiver right there at Park, although at 315 MHz, I just chose the cheaper one:
The website with the encoder has everything you need - the circuit itself, a printed circuit board “for ironing” and a whole bunch of firmware with various costs.

The body of the remote control is soldered from fiberglass, the sticks were taken from a helicopter remote control with IR control, it was also possible from a computer gamepad, but my wife would kill me, she plays “DmC” on it, the battery compartment is from the same remote control.

There is a receiver, but in order for the car to move, you also need a decoder (channel decoder), so I had to look for it for a very long time - even Google was sweating, well, as they say, “let the seeker find” and here it is: http://homepages .paradise.net.nz/bhabbott/decoder.html

There are also firmwares for MK.

Regulator: Initially I made the simpler one:

But driving only in front is not ice and this one was chosen:

Link to website: http://vrtp.ru/index.php?showtopic=18549&st=600
The firmware is also there.

I searched through a mountain of motherboards and video cards and did not find the necessary transistors, namely for the upper arm (P-channel), so the H-bridge (this is the unit that powers the motor) was soldered on the basis of a Toshiba microcircuit from the “TA7291P” video recorder,

the maximum current is 1.2A - which suited me quite well (not TRAXXAS - I do it), I drew the board with a marker for 20 rubles, etched it with ferric chloride, soldered it from the side of the tracks. This is what happened.

“Pure” PRM is emitted into the air, of course this is not good, I won’t put this on an airplane, but for a toy it will do just fine.
The car was taken from the factory, from the Chinese brothers, the entire tribune except the running engine was removed and in its place they put in my and Ivan’s project, even though we are busy with it separately, it was his idea!

Spent:
Set of RF modules – 200 RUR
Two PIC12F675 MKs - 40 rubles each.
Serva - TG9e 75r
+3 pm.

If you have any questions, I’ll be happy to answer (I didn’t write about many things)
Best regards, Vasily.

For radio control of various models and toys, discrete and proportional action equipment can be used.

The main difference between proportional-action equipment and discrete equipment is that it allows, at the operator’s commands, to deflect the model’s rudders to any desired angle and smoothly change the speed and direction of its movement “Forward” or “Backward”.

The construction and installation of proportional-action equipment is quite complex and is not always within the capabilities of a novice radio amateur.

Although discrete-action equipment has limited capabilities, they can be expanded by using special technical solutions. Therefore, next we will consider single-command control equipment suitable for wheeled, flying and floating models.

Transmitter circuit

To control models within a radius of 500 m, as experience shows, it is enough to have a transmitter with an output power of about 100 mW. Transmitters for radio-controlled models typically operate within a range of 10 m.

Single-command control of the model is carried out as follows. When a control command is given, the transmitter emits high-frequency electromagnetic oscillations, in other words, it generates a single carrier frequency.

The receiver, which is located on the model, receives the signal sent by the transmitter, as a result of which the actuator is activated.

Rice. 1. Schematic diagram of the radio-controlled model transmitter.

As a result, the model, obeying the command, changes the direction of movement or carries out one instruction that is pre-built into the design of the model. Using a single-command control model, you can make the model perform quite complex movements.

The diagram of a single-command transmitter is shown in Fig. 1. The transmitter includes a master high-frequency oscillator and a modulator.

The master oscillator is assembled on transistor VT1 according to a three-point capacitive circuit. The L2, C2 circuit of the transmitter is tuned to the frequency of 27.12 MHz, which is allocated by the State Telecommunications Supervision Authority for radio control of models.

The DC operating mode of the generator is determined by selecting the resistance value of resistor R1. The high-frequency oscillations created by the generator are radiated into space by an antenna connected to the circuit through the matching inductor L1.

The modulator is made on two transistors VT1, VT2 and is a symmetrical multivibrator. The modulated voltage is removed from the collector load R4 of transistor VT2 and supplied to the common power circuit of transistor VT1 of the high-frequency generator, which ensures 100% modulation.

The transmitter is controlled by the SB1 button, connected to the general power circuit. The master oscillator does not operate continuously, but only when the SB1 button is pressed, when current pulses generated by the multivibrator appear.

High-frequency oscillations created by the master oscillator are sent to the antenna in separate portions, the repetition frequency of which corresponds to the frequency of the modulator pulses.

Transmitter parts

The transmitter uses transistors with a base current transfer coefficient h21e of at least 60. Resistors are MLT-0.125 type, capacitors are K10-7, KM-6.

The matching antenna coil L1 has 12 turns PEV-1 0.4 and is wound on a unified frame from a pocket receiver with a tuning ferrite core of grade 100NN with a diameter of 2.8 mm.

Coil L2 is frameless and contains 16 turns of PEV-1 0.8 wire wound on a mandrel with a diameter of 10 mm. An MP-7 type microswitch can be used as a control button.

The transmitter parts are mounted on a printed circuit board made of foil fiberglass. The transmitter antenna is a piece of elastic steel wire with a diameter of 1...2 mm and a length of about 60 cm, which is connected directly to socket X1 located on the printed circuit board.

All transmitter parts must be enclosed in an aluminum housing. There is a control button on the front panel of the case. A plastic insulator must be installed where the antenna passes through the housing wall to socket XI to prevent the antenna from touching the housing.

Setting up the transmitter

With known good parts and correct installation, the transmitter does not require any special adjustment. You just need to make sure that it is working and, by changing the inductance of the L1 coil, achieve maximum transmitter power.

To check the operation of the multivibrator, you need to connect high-impedance headphones between the VT2 collector and the plus of the power source. When the SB1 button is closed, a low-pitched sound corresponding to the frequency of the multivibrator should be heard in the headphones.

To check the functionality of the HF generator, it is necessary to assemble a wavemeter according to the diagram in Fig. 2. The circuit is a simple detector receiver, in which coil L1 is wound with PEV-1 wire with a diameter of 1...1.2 mm and contains 10 turns with a tap from 3 turns.

Rice. 2. Schematic diagram of a wave meter for setting up the transmitter.

The coil is wound with a pitch of 4 mm on a plastic frame with a diameter of 25 mm. A DC voltmeter with a relative input resistance of 10 kOhm/V or a microammeter for a current of 50...100 μA is used as an indicator.

The wavemeter is assembled on a small plate made of foil fiberglass laminate 1.5 mm thick. Having turned on the transmitter, place the wave meter at a distance of 50...60 cm from it. When the HF generator is working properly, the wave meter needle deviates at a certain angle from the zero mark.

By tuning the RF generator to a frequency of 27.12 MHz, shifting and spreading the turns of the L2 coil, the maximum deflection of the voltmeter needle is achieved.

The maximum power of high-frequency oscillations emitted by the antenna is obtained by rotating the core of the coil L1. Setting up the transmitter is considered complete if the voltmeter of the wave meter at a distance of 1...1.2 m from the transmitter shows a voltage of at least 0.05 V.

Receiver circuit

To control the model, radio amateurs quite often use receivers built according to a super-regenerator circuit. This is due to the fact that the super-regenerative receiver, having a simple design, has a very high sensitivity, on the order of 10...20 µV.

The diagram of the super-regenerative receiver for the model is shown in Fig. 3. The receiver is assembled on three transistors and is powered by a Krona battery or another 9 V source.

The first stage of the receiver is a super-regenerative detector with self-quenching, made on transistor VT1. If the antenna does not receive a signal, then this cascade generates pulses of high-frequency oscillations, following with a frequency of 60...100 kHz. This is the blanking frequency, which is set by capacitor C6 and resistor R3.

Rice. 3. Schematic diagram of a super-regenerative receiver of a radio-controlled model.

Amplification of the selected command signal by the super-regenerative detector of the receiver occurs as follows. Transistor VT1 is connected according to a common base circuit and its collector current pulsates with a quenching frequency.

If there is no signal at the receiver input, these pulses are detected and create some voltage on resistor R3. At the moment the signal arrives at the receiver, the duration of the individual pulses increases, which leads to an increase in the voltage across resistor R3.

The receiver has one input circuit L1, C4, which is tuned to the transmitter frequency using the coil core L1. The connection between the circuit and the antenna is capacitive.

The control signal received by the receiver is allocated to resistor R4. This signal is 10...30 times less than the blanking frequency voltage.

To suppress interfering voltage with a quenching frequency, a filter L3, C7 is included between the super-regenerative detector and the voltage amplifier.

In this case, at the filter output, the voltage of the blanking frequency is 5... 10 times less than the amplitude of the useful signal. The detected signal is fed through separating capacitor C8 to the base of transistor VT2, which is a low-frequency amplification stage, and then to an electronic relay assembled on transistor VTZ and diodes VD1, VD2.

The signal amplified by the transistor VTZ is rectified by diodes VD1 and VD2. The rectified current (negative polarity) is supplied to the base of the VTZ transistor.

When a current appears at the input of the electronic relay, the collector current of the transistor increases and relay K1 is activated. A pin 70...100 cm long can be used as a receiver antenna. The maximum sensitivity of a super-regenerative receiver is set by selecting the resistance of resistor R1.

Receiver parts and installation

The receiver is mounted using a printed method on a board made of foil fiberglass laminate with a thickness of 1.5 mm and dimensions of 100x65 mm. The receiver uses the same types of resistors and capacitors as the transmitter.

The superregenerator circuit coil L1 has 8 turns of PELSHO 0.35 wire, wound turn to turn on a polystyrene frame with a diameter of 6.5 mm, with a tuning ferrite core of grade 100NN with a diameter of 2.7 mm and a length of 8 mm. The chokes have inductance: L2 - 8 µH, and L3 - 0.07...0.1 µH.

Electromagnetic relay K1 type RES-6 with a winding resistance of 200 Ohms.

Receiver setup

Tuning the receiver begins with a super-regenerative cascade. Connect high-impedance headphones in parallel with capacitor C7 and turn on the power. The noise that appears in the headphones indicates that the super-regenerative detector is working properly.

By changing the resistance of resistor R1, maximum noise in the headphones is achieved. The voltage amplification cascade on transistor VT2 and the electronic relay do not require special adjustment.

By selecting the resistance of resistor R7, a receiver sensitivity of about 20 μV is achieved. The final configuration of the receiver is carried out together with the transmitter.

If you connect headphones in parallel to the winding of relay K1 in the receiver and turn on the transmitter, then a loud noise should be heard in the headphones. Tuning the receiver to the transmitter frequency causes the noise in the headphones to disappear and the relay to operate.