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

More stable parameters with the same simplicity (in terms of the number of parts) can be achieved if the receiving path is built according to a superheterodyne circuit on an integrated circuit. But specialized chips for communication equipment are not always available. But for sure, every radio amateur has a K174XA34 chip or even a ready-made broadcasting receiving path based on it. Some time ago there was a simpleton craze for the design of VHF-FM broadcast receivers based on it. Now many of them have been sent "to the far shelf."

Let me remind you that the K174XA34 chip (analogous to 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 be limited to just one circuit, a heterodyne one. Get rid of LC or piezoceramic IF filters (filters are made on the op-amp according to RC circuits). And the result is a receiving path that requires almost no tuning - if everything is soldered correctly 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 extra leads, or leaving two holes empty. You just need to mentally imagine that the 18-pin package does not have pins 9 and 10. If you do not take them into account, then by numbers everything is like in the 16-pin version. I had a chip in a 16-pin package.

And so, the 16-pin version has pin 9 (the same pin 11 for the 18-pin), and 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 key 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 K174XA34 and use the 9th output (Fig. 1). Now it remains only to tune the receiving path to the desired frequency with the L1-C2 circuit. And adjust the threshold of the relay with the resistor R2.
The receiver antenna can be of any design - it depends on the place 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.

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

Setting the frequency of the transmitter coil L1. The depth of the PIC can be changed by changing the ratio of capacitors C2 and C3 (it will be more convenient if you replace them with trimmers). Then you need to fine-tune the frequency again.
The operating mode of the cascade is set experimentally by the resistor R1 for the best return, but the current consumption should not exceed 50 mA.

Details. The local oscillator coil of the receiving path is frameless. Its inner 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 inner 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 winding of 5V. If you need to work with a relay with a winding for 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 the capacitor C14.

In this article, you will see how to make a radio control for 10 commands with your own hands. Range this device 200 meters on the ground and over 400 meters in the air.

The scheme was taken from the site vrtp.ru
Transmitter

Receiver

The buttons can be pressed in any sequence, although everything works stably at once. With it, you can control various loads: garage doors, lights, aircraft models, cars, and so on ... In general, anything, it all depends on your imagination.

To work, we need a list of parts:
1) PIC16F628A-2 pcs (microcontroller) (link to aliexpress) pic16f628a )
2) MRF49XA-2 pcs (radio transmitter) (link to aliexpress) MRF49 XA )
3) Inductor 47nH (or wind it yourself) - 6pcs
Capacitors:
4) 33uF (electrolytic) - 2 pcs
5) 0.1UF-6pcs
6) 4.7 pF-4 pcs
7) 18 pF-2 pcs
Resistors
8) 100 ohm-1pc
9) 560 ohm - 10 pcs
10) 1 set - 3 pieces
11) 1 LED
12) buttons - 10 pcs
13) Quartz 10MHz-2 pcs
14) Textolite
15) Soldering iron
As you can see, the device consists of a minimum of parts and is within the power of everyone. You just have to want. The device is very stable, after assembly it works immediately. The circuit can be done as on a printed circuit board. So and hinged mounting (especially for the first time, it will be easier to program). First, we make a payment. Print out

And we charge a fee.

We solder all the components, it is better to solder the PIC16F628A last, since it will still need to be programmed. Solder the MRF49XA first.

The main thing is very neat, she has very subtle conclusions. Capacitors for clarity. The most important thing is not to confuse the poles on the 33 microfarad capacitor, since it has different conclusions, one +, the other -. Solder all other capacitors as you wish, they have no polarity on the terminals

Coils can be used purchased 47nH but it is better to wind it yourself, they are all the same (6 turns of 0.4 wire on a 2 mm mandrel)

When everything is soldered, we check everything well. Next, we take PIC16F628A, it needs to be programmed. I used PIC KIT 2 lite and a homemade socket
Here is the link to the programmer Pic Kit2 )

Here is the wiring diagram

It's all simple, so don't be intimidated. For those who are far from electronics, I advise you not to start with SMD components, but to buy everything in DIP size. I did it myself for the first time

And it really worked the first time.

Open the program, select our microcontroller

I settled on unlocking the fourth axis of control and installing a bunch of buttons, switches and LEDs in the console. Then it was up to the circuit, soldering iron and firmware. As it turned out later, the buttons and connectors were not enough, I had to reinstall.

Diagram of a homemade radio remote control

The circuit is based on the Atmega8 microcontroller. His legs were literally enough "back to back". To see a large diagram - click on the picture (the diagram is also located in the archive, which is at the end of the article.

Let's calculate: 10 buttons / switches + 2 LEDs + 2 legs per quartz (we need a time-accurate PWM signal) + 5 channels of ADC + 2 legs on UART + 1 channel to output the PPM signal to the RF module = 22 MK legs. Just as much as the Atmega8 has, which is configured for in-circuit programming (I mean the RESET pin, aka PC6).

I connected the LEDs to PB3 and PB5 (MOSI and SCK programming connectors) Now, while uploading the firmware, I will observe a beautiful wink (useless in a sense - but here I was chasing a beautiful visual effect).

Let me remind you how it all started - I had an RF module from Hobicking's equipment (it was replaced by the FrSky RF module), and there was helicopter equipment. Since there were no knobs in the equipment (and why should they?), it turns out out of six channels I will normally (normally) use only 4 (two for each stick). I decided to spend one channel on 8 independent buttons / switches, another one - to programmatically simulate the rotation of the twist (for example - a beautiful chassis release - I clicked the switch, and the chassis was released for 10 seconds). Another switch is still undecided what to do with it.
LEDs showing the state of the switches - work independently of the microcontroller. One of the software-controlled LEDs is responsible for indicating a low battery, the second one shows the current state of the software twist.

In addition to buttons and LEDs, I also wanted to add a standard (for me) UART connector to the case (for communication with a PC, then I will write my own setup program), and a connector with a PPM signal output for connecting the remote control to the simulator. Having suffered with the connector for the programmer, I realized that it didn’t suit me, and also brought it out. The only thing that is bad about this is that there is a danger of shorting the connector pins, although they are "drowned" in the case. But this can be treated with 220 ohm series resistors (which gives a 99% guarantee that the microcontroller will remain intact)

When I came close to using the equipment, I realized that I had forgotten about the Bind button (when pressed, the transmitter switches to the receiver search mode). I had to add this

The printed circuit board of the controller of the radio remote control

Very unpretentious - most of the legs are simply brought out. There is a 5 volt stabilizer on the board, and an input voltage measurement circuit. Why use a DIP package? I just had it ... besides - why not DIP ...

When I was soldering all this, a thought came through - would this cloud of wires work ?!
But still it works. Usually my boards are clean of rosin ... but here I was constantly fiddling with the divider, until it turned out that I had a software problem and not an “iron one”. Powered by a two-jar lipolka (what once remained from a normal three-jar after it was forgotten to be disconnected from the load. As a result, one of the cans went into full discharge). Despite this, he provided for the possibility of working from finger batteries. You never know

As a result, I got a four-channel equipment with my own firmware, in which I can change everything I want. That's about the firmware and software I'll write later.

And now you can download the current firmware version. So far, it is not configurable at all (i.e. there are no settings for reverse, costs, offsets and other “goodies” yet). The state of the knobs is simply read and a PPM signal is generated. Buttons and switch MOD does not work yet. But the virtual servo works (on channel 5) and the measurement of the input voltage level. If it is too low, the IND LED will start flashing (the firmware automatically determines how many cans the lithium polymer battery has). And yet - the costs for channel 4 (where I added my potentiometer) are too high to compensate for the incomplete range of rotation of the potentiometer.

This article is a modeler's story about making a homemade RC Range Rover 4x4 from a plastic model. It reveals the nuances of manufacturing axle drives, installing electronics and many other nuances.

So, I decided to make a car model with my own hands!

I bought an ordinary bench model Range Rover in the store. The price of this model is 1500 rubles, in general it is a little expensive, but the model is worth it! Initially I thought about making a hammer, but this model is much more suitable in design.

I had electronics, well, I took some parts from a trophy called "cat" which I had not needed for a long time and was disassembled for parts!

Of course, it was possible to take other prefabricated models as a basis, but I wanted just such an off-road jeep.

It all started with bridges and differentials that I made from copper pipes and soldered with a regular 100w soldering iron. The differentials here are ordinary, the gear is plastic, the rods and drive bones are iron from the trophy.

These tubes can be purchased at any hardware store.


I took the differential gear from a regular printer. I didn’t need him for a long time and now I decided that it was time for him to rest.

Everything turned out pretty reliably, but it’s rather inconvenient to work with a soldering iron!

After I made the differentials, I had to close them with something, I closed them with pill caps.

And painted it with regular car paint. It turned out beautifully, although beauty is hardly needed for a trophy.

Then it was necessary to make steering rods and put bridges on the frame. The frame was included and to my surprise it turned out to be iron, not plastic.

It was not easy to do this, since the scale of the parts is very small and it was not possible to solder here, I had to bolt it. Steering rods I took from the same old trophy that I dismantled.

All parts of the differentials are on bearings. Since I made the model for a long time.

I also ordered a gearbox with a reduction gear, the gear will be switched on by a microservo machine from the remote control.

Well, in general, then I installed a plastic bottom, cut a hole in it, installed a gearbox, cardan shafts, a home-made gearbox, an ordinary collector engine for such a small model, it makes no sense to put a bc and the speed is not important to me.

The engine is from a helicopter, but in the gearbox it is quite powerful.

The most important thing is that the model does not move in jerks, but smoothly without delay, the gearbox was not easy to make, but I had a heap of details, the main thing is ingenuity.

The reducer was screwed to the bottom, it kept perfectly, but to attach the bottom to the frame I had to tinker.

Then I installed electronics, shock absorbers, battery. At first I installed the electronics rather weak and the regulator and the receiver were a single unit, but then I installed everything separately and the electronics were more powerful.

And finally, painting, installation of all the main components, decals, headlights, and more. I painted everything with regular plastic paint in 4 coats then painted the fenders brown and sanded the parts to give a shabby and worn look.

The body of the model and the color are completely original, I found the color on the Internet and the photo of the real car did everything according to the original. This color combination exists on a real car and was painted in this color at the factory.

Well, here are the final photos. I will add a video with the test a little later, and the model turned out to be very passable, the speed was 18 km / h, but I did it not for speed. In general, I am satisfied with my work, and it is up to you to evaluate it.

The machine is not large, the scale is 1x24 in size and there is the whole point of the idea, I wanted a mini trophy for myself.

The model is not afraid of moisture! Germetil himself simply varnished the electronics, very reliably, no moisture is terrible.

Servo machine micro park from the aircraft for 3.5 kg.

The battery lasts for 25 minutes of riding, but I will install more powerful electronics and a battery, because this one is not quite enough.

Even the bumpers are the same as on the original. And fastenings on them too. The drive on it is not 50-50%, but 60-40%.

In general, the Range Rover turned out in a rustic style, I didn’t even think that it would turn out to be so high-quality to paint because I really don’t know how to paint, although there’s nothing difficult!

I forgot to add for the sake of beauty, I also installed a roll cage and a full spare tire. Spare wheel and frame were included with the kit.

More about radio-controlled models:

Misha comments:

Tell me how the four-wheel drive is arranged, what is inside the bridge besides the transfer case? There must be a steering knuckle after all.

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

The main difference between proportional and discrete equipment is that it allows, at the operator's command, to deflect the model's rudders to any required angle and smoothly change the speed and direction of its movement "Forward" or "Back".

The construction and adjustment of proportional action equipment is quite complex and not always within the power of a novice radio amateur.

Although discrete action equipment has limited opportunities, but by applying special technical solutions, they can be expanded. Therefore, further 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, experience shows that it is enough to have a transmitter with an output power of about 100 mW. RC model transmitters typically operate within a 10m range.

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 one 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 triggered.

Rice. 1. circuit diagram radio controlled transmitter.

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

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

The mode of operation of the generator for direct current is determined by the selection of the resistance value of the resistor R1. The high-frequency oscillations created by the generator are radiated into space by an antenna connected to the circuit through a 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 the transistor VT2 and fed into the common power circuit of the transistor VT1 of the high-frequency generator, which ensures 100% modulation.

The transmitter is controlled by the SB1 button included in the common power circuit. The master oscillator does not work continuously, but only when the SB1 button is pressed, when current pulses appear, generated by the multivibrator.

The 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 details

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

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

The L2 coil is frameless and contains 16 turns of PEV-1 0.8 wire wound on a mandrel with a diameter of 10 mm. As a control button, you can use a microswitch type MP-7.

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

All parts of the transmitter must be enclosed in an aluminum case. The control button is located on the front panel of the case. A plastic insulator must be installed at the point 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. It is only necessary to make sure that it works and, by changing the inductance of the coil L1, to achieve the maximum power of the transmitter.

To check the operation of the multivibrator, you must turn on 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 operability of the RF generator, it is necessary to assemble the wavemeter according to the scheme of Fig. 2. The circuit is a simple detector receiver, in which the L1 coil 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 the wavemeter 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. As an indicator, a DC voltmeter with a relative input resistance of 10 kOhm / V or a microammeter for a current of 50 ... 100 μA is used.

The wavemeter is assembled on a small plate of foil fiberglass with a thickness of 1.5 mm. Turning on the transmitter, place the wavemeter from it at a distance of 50 ... 60 cm. With a working RF generator, the wavemeter needle deviates by some angle from the zero mark.

By tuning the RF generator to a frequency of 27.12 MHz, shifting and expanding the turns of the L2 coil, the maximum deviation 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. The transmitter tuning is considered completed if the wavemeter voltmeter 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 the super-regenerator scheme. 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 scheme 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 other 9 V source.

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

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

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

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

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

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

To suppress interfering voltage with a quenching frequency, a filter L3, C7 is connected between the superregenerative detector and the voltage amplifier.

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

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

When current appears at the input of the electronic relay, the collector current of the transistor increases and relay K1 is activated. As a receiver antenna, you can use a pin with a length of 70 ... 100 cm. The maximum sensitivity of the super-regenerative receiver is set by selecting the resistance of the resistor R1.

Details and installation of the receiver

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

The coil of the L1 super-regenerator circuit 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 brand 100NN with a diameter of 2.7 mm and a length of 8 mm. Chokes have inductance: L2 - 8 μH, and L3 - 0.07 ... 0.1 μH.

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

Receiver setup

Receiver tuning begins with a super-regenerative stage. Connect high-impedance headphones in parallel with capacitor C7 and turn on the power. The noise that appeared in the headphones indicates the correct operation of the super-regenerative detector.

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

By selecting the resistance of the resistor R7, a receiver sensitivity of the order of 20 μV is achieved. The final adjustment of the receiver is made together with the transmitter.

If you connect headphones in parallel with the winding of relay K1 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.