What is a radio controlled car made of? Chinese radio-controlled car
Such a system was conceived for a friend who wanted to drive a car from a distance. Manage is too strong a word because scheme was designed to drive just two 15 amp loads. I decided not to torture myself and bought a ready-made radio control module for two teams. This scheme is from a Chinese typewriter with a range of 15-20 meters, the typewriter itself costs only $5.
The module can execute two commands, designed to work with the electric motor of the machine. When moving back and forth, only a polarity reversal occurs, so it was necessary to conceive a circuit that could work with two separate loads, while only due to a polarity reversal of the input signal. Everything that is presented below is completely the author's development and is published in the set for the first time. Go!
So, the task was to make two independent channels of electronic switches, let's consider the operation of one of the channels. When commanded from the control panel, the radio module sends a signal to the switch circuit, which activates the load, the load should be turned off only when the command is repeated from the control panel, therefore, it was necessary to make a permanent button circuit.
This scheme can easy to implement on your favorite 555 timer, it works in a wide range of input voltages, no jambs or failures during operation have been observed so far. The signal is amplified by a powerful bipolar transistor KT818, although you can also use medium power from the KT814/816 series, since the transistor itself is designed to control the relay. The relay is selected for the desired current (in my case, 15 Amperes). Similar relays can be obtained from uninterruptible power supplies or bought at an auto parts store, they cost about $ 3
During operation, the transistor does not heat up, so there is no need for an additional heat sink.
Two separate channels were assembled on compact breadboards, everything worked perfectly. Now the question was - we have two channels, and the radio module can only power one. To do this, it was decided to take a tricky step - the switch circuits are activated only if you press the buttons, and instead of the buttons we will have optocouplers. At the first command, a direct signal goes to the first optocoupler, which works, by that time the second one does not work, since the built-in emitter is connected in the opposite direction.
The circuit itself can also work from a reduced voltage source. The whole circuit turns out to be quite compact and can be mounted in any convenient plastic case. Literally any optocouplers are suitable, for example, from computer power supplies (in other words, they can be found literally in any switching power supplies).
In such a simple way, I managed to solve the task, although in the future the radio module was replaced with a more powerful one.
A load of up to 15 Amperes is already connected to the relay contacts, a friend uses the system to activate the illumination of the car interior, the second command was needed to remotely turn on the subwoofer - everything that is simple is ingenious, but I say goodbye to you, but not for long ...
Any modeler should understand how his model works. This is simply necessary, since it will periodically need to be maintained, adjusted and repaired. In this article, we will look at what parts it consists of. Components of the car:
- Chassis
- Suspension
- Power point
- Energy source
- Transmission
- Servo drives
- wheels
- Body
- Radio control equipment
Chassis
The chassis is the basis of any radio-controlled car. As a rule, this is a metal or plastic plate to which all other elements are attached. Chassis in the form of a metal plate is used on buggies and truggies, plastic and carbon on road models. Monster and crawler models usually have the most complex chassis in the form of one or more intricately shaped parts. Often, the word "chassis" also means the chassis of the model complete with suspension and transmission.
Plastic chassis type "bath"
Suspension
The suspension of the model provides a smooth ride of the car when passing bumps, constant contact of the wheels with the road to improve handling, and for off-road models, it also absorbs shock when landing after jumps. The suspension of most models uses oil-filled shock absorbers mounted vertically, one for each wheel. In simple models, friction shock absorbers can be used. Some monsters have two shock absorbers for each wheel.
Power point
The role of the power plant of the model model can be performed by an electric motor or an internal combustion engine (ICE). The power plant of the electric model consists of a motor and a speed controller. If there are usually no questions about the purpose of the motor, then the function of the speed controller is not always immediately clear. In short, the regulator is an intermediate link between the battery and the motor, providing the right voltage to the motor contacts so that it rotates at the required speed. Electric motors can be divided into two types: collector and brushless. The collector engine in car modeling can be considered somewhat outdated, but power plants based on it are much cheaper and are used quite often. The disadvantage of this type of motor is the presence of brushes, which wear out rather quickly and the motors require constant maintenance (or replacement) during intensive use. Brushless motors are more expensive, powerful, and virtually maintenance-free. The main external difference between a brushless motor and a collector motor is that it has three wires instead of two.
Internal combustion engines used in car models can be divided into incandescent and gasoline. Most models are equipped with incandescent internal combustion engines, they operate on special fuel. Not on petrol! The working volume of the glow engine usually varies from 2 to 6 cubic centimeters. Often the volume is indicated in cubic inches, for example: an engine with a volume of 0.21 cubic inches (it can also be called "twenty-first", naming only hundredths of the volume in inches) \u003d 3.44 cm 3.
Gasoline engines are used on large scale models, this is due to the fact that the minimum volume of a gasoline engine is about 20 cm 3, it is quite large and heavy. Typically, engines with a volume of 20-30 cm 3 are used.
Gasoline engines develop significantly less power per cubic centimeter of their volume, but have more torque and are much more economical.
Most car engines are single cylinder.
Glow engine 0.21 in 3
Gasoline engine 23 cm3
Energy source
Electric cars run on batteries (not batteries like toys). The most commonly used battery types are NiMH and LiPo. The voltage from which the car works is usually from 7.4 to 22.2 volts. When choosing a battery, you should take into account the characteristics of the speed controller installed on the model, the type of battery and its voltage will depend on it.
Special fuel for glow engines consists of methanol, nitromethane and oil. Extreme care must be taken when handling this fuel - methyl alcohol is extremely poisonous! The cost of such fuel is quite high, about 200-500 rubles per liter. The standard tank of the model, with a volume of 120-150 cm 3, is consumed in about 10 minutes (depending on the engine size, there are real gluttons).
Just like incandescent, two-stroke model gasoline engines, it means that they must be filled with a mixture of gasoline and a special oil for two-stroke engines. The path behind him lies in any petrol equipment store.
Transmission
The transmission transmits power from the engine to the wheels. To transmit torque, gears, cardans and belts are used. Most models have four-wheel drive (4WD), although rear-wheel drive (2WD) models are also quite common. Differentials are installed between the wheels on the same axle, and often also a center differential.
Servo drives
To turn the wheels when taxiing, as well as to control the gas and brakes on models with internal combustion engines, servos are used (in the common people - "servos", in English "servo"). Servos are small boxes with an electric motor and gear that can turn their output shaft to a given angle and hold it in that position.
Servo internals
wheels
Unlike the wheels of a real car, the wheels of car models are not inflated with air, its role is played by soft inner inserts. When choosing wheels for a sports car, you should be guided only by their characteristics, and not by their appearance. Beautiful wheels with chrome-plated spokes and a powerful tread can only be afforded by monsters and drift models. Models designed for racing are content with solid discs without spokes and tires with a special small tread.
Body
The body of the vast majority of car models is made of Lexan - a thin, durable and flexible sheet of transparent plastic. This body is very light and perfectly protects the model in collisions and coups. Lexan bodywork is painted with special paints from the inside. The Lexan body is mounted on special racks and secured with clips. Unlike a real car, such a body is not an integral part of the model and can be easily replaced with another one. Therefore, it is almost pointless to choose a model only on the body or say "I bought a Porsche 911 model." With intensive use, a model can change several bodies in its life, gradually becoming unusable.
Radio control equipment
And, finally, the model becomes radio-controlled only when radio control equipment or simply "equipment" is installed on it. The equipment consists of two parts - transmitter and receiver. To control car models, as a rule, a pistol-type transmitter is used, the trigger of which controls acceleration and brake, and the steering wheel controls the rotation of the model. On the market there is a huge selection of the most diverse equipment costing from a couple of tens to several hundred dollars. Recently, almost all new equipment operates at a frequency of 2.4 GHz, while many models can be launched simultaneously in one place without interfering with each other.
Conclusion
If you are buying a ready-to-run model (RTR, Ready to Run, Ready to Race), then you will only need to purchase batteries or fuel. And professional models are often supplied in the form of a self-assembly kit (Kit), which, at a minimum, will also require equipment and a power plant.
Previously, there was not even close to such an abundance of goods in general and toys in particular. And in many ways, the modern children's paradise is due to progress in electronics. Talking robots, multicopters - all this is not just in stores, but is sold at a very inexpensive price, for many. In addition, toys are sometimes so advanced in terms of electronic filling and interesting in work that it’s time to buy them not for children, but for yourself. Especially if the father is a radio amateur :) In general, by chance passing by the shop window "Everything for a Dollar" I noticed a box with a Chinese radio-controlled car, which cost only $ 10! Naturally, this is for the whole set.
Complete set of R/U machines
- Car - racing car
- Remote control
- Four 1.2V 600mAh batteries
- Charger 4.8V 250mA
Characteristics of a car on radio control
- Machine food - 4 pcs. 1.2V nickel cadmium batteries
- Remote control power - 3 AA batteries
- Charging time - 5 hours
- Working time - half an hour
- Radio channel frequency - 27 MHz
- Range of the radio channel - 10 meters
On the box everything is written in Chinese - not a single not only Russian - not even an English word. Well, it's time to learn Chinese or develop intuition :) In theory, there is nothing complicated: I put batteries in the car, three batteries in the remote control - and off we go.
Machine control panel
Please note that the kit does not include batteries for the remote control, only for the car. So you need 3 AA elements of 1.5 V.
The remote control immediately attracted attention with the complete absence of buttons, not counting the power button.
The thing is that here the commands to turn left and right, move forward and backward, are given by tilt. If you open the remote control and examine the board with parts, you can see 4 position sensors. Inside these cylinders, soldered with an inclination, there are sensors in the form of balls.
The DIP transmitter chip itself, like the rest of the parts, is why the remote control is very compact and lightweight. A 3-knee telescopic antenna is bolted to it in front. It is long when unfolded - about 30 cm. If you are standing next to the car - you can not unfold it. But at a distance of more than 5 m, this is necessary.
Radio-controlled car
Before you install the batteries in the battery compartment of the car, you need to charge them. To do this, the kit includes a small charger, naturally pulsed.
The board inside it is a copy of the usual charging from a mobile phone. And the parameters (and circuit) are similar - a pulse converter on a transistor of about 2-3 watts.
When you turn on the button of the machine (it is on the bottom), all 4 wheels will immediately start flashing blue and red LEDs installed from the inside. It is both beautiful and convenient - it is immediately clear that the power is activated. So that there is no situation in which they played and forgot to de-energize the car by planting or even ditching the batteries.
Let's take it apart and take a look under the cover. The receiving part is assembled on the basis of a microcircuit RX-2B. You can turn on the circuits, they are standard for most radio-controlled models of 27 MHz, short range.
And the C945 transistors switch two motors - the main one, which is located in the back of the car, and the auxiliary one, which is responsible for turning the front wheels.
The front headlights come on when the car is moving forward. When reversing, they immediately go out. It is interesting that not LEDs were used here, but light bulbs. This is of course more realistic, but the power consumption increases by almost 100 mA, so to save money, I simply cut the wires going to them from the control board with scissors.
Video of the machine
In general, the Chinese once again surprise not so much with technology, although they keep their finger on the pulse and constantly replenish the market with new interesting devices, but with an outrageously low price. Think about how much 4 batteries would cost separately? And the charger? Not to mention the rest. As for the quality: the child has been playing for more than a month and nothing, the car is alive and well, although it has already been recharged 20 times.
The best price for an RC car can only be if the car is self-made, mostly from junk and with a few inexpensive parts. Previously, cars made on Arduino were already considered, which has a small price, but the cost can be further reduced if you use not a ready-made board, but a home-made one with an ATmega8 microcontroller. The ATmega8s were in older versions of the Arduino which had less features than the new ones, but nevertheless, in the older versions of the Arduino, the features are more than enough to create an RC car. If you load the Arduino bootloader into the ATmega8, then this microcontroller "turns" into almost an Arduino and this makes it possible to use the Arduino IDE development environment with libraries for nrf24l01 + radio modules, SG09 servo motors and generally easier code writing, which greatly simplifies the whole process of creating a radio-controlled machine. At a time when microcontrollers were not as widespread as they are now, making electronics for a radio-controlled car was a very difficult thing, but now this business is available to a much larger number of people. In addition, self-creation of the machine makes it possible to make it what it should be, supplement and improve "to your taste." Consider the transmitter circuit.
Figure 1 - Transmitter
The NRF24L01+ radio module is connected to the microcontroller via SPI, the R2 potentiometer is a steering wheel on the remote control and its middle output is connected to one of the microcontroller’s ADC pins (Arduino IDE allows you not to write too cumbersome code to use the built-in analog to digital converter (ADC)). Buttons to control movement, headlights and flasher are connected to digital inputs and without additional pull-up resistors. the microcontroller has built-in ones and their conductivity is enough in this case. The quartz resonator is set to 16 MHz, if the quartz resonator is set to this frequency, then the bootloader for Arduino NG can be loaded into the ATmega8. There is also an SB2 reset button.
Figure 2 - Receiver
To control the motor, the L293D driver is used, which can output up to 600mA, so if the motor consumes more current, then another more powerful driver is needed. Two film capacitors C3, C4 with a capacity of 470nF each are connected to the terminals of the electric motor, if these capacitors are not installed, the motor will create great interference and the machine will not work as it should. Also, capacitors are placed between the power plus and ground (supply zero, power minus), capacitor C6 with a capacity of 470nF is placed directly on the power terminals of the NRF24L01+ radio module, capacitor C7 is placed elsewhere on the board. The circuit is powered by one lithium-ion battery with a voltage of 3.7V, which can be obtained, for example, from a power bank, which can also be used as a charger for this battery (the main thing to remember is where you need to put the plus of the battery and where the minus). Red LEDs are connected to one of the outputs of the L293D driver, which indicate the movement of the machine backwards, if after assembly these LEDs light up when the machine moves forward, then you need to connect these LEDs to another output of the driver. The SG09 servomotor is used to turn the front wheels. The servomotor for this purpose turned out to be better than a stepper motor. the servomotor does not need a driver (it is inside the servomotor), only one pin of the microcontroller is used to control the servo motor (4 pins need to be spent on the stepper motor), the servo motor works faster than the stepper motor, you can make more convenient control with it, it is also cheaper, lighter, in general you can forget about using a stepper motor for turns. Two white LEDs VD1 and VD2 are the headlights of the car that can be turned on by pressing the corresponding button, so that you do not have to keep the button pressed all the time when the headlights are on - instead of a button, you can put a switch or a button with fixation. The headlights turn on through the transistor. the current consumed by the two LEDs is too high for the microcontroller. Also in the car there is a flasher and a siren. A flasher is an RGB LED that shines alternately with blue or red light, Siren is a low-power piezo speaker that is connected directly to the outputs of the microcontroller. The speaker must be PIEZOELECTRIC and low power if you put a speaker with a winding, then it may have too low active resistance; moreover, when switching on the winding, large voltage surges occur, which can lead to burnout of the microcontroller. From the diagrams above, it can be seen that there are still free conclusions on the microcontrollers of the transmitter and receiver, which means that the machine can still be supplemented with some elements, for example, you can put a shooting tower, bucket or claw on servomotors, additional LEDs, etc.
Sketches can be downloaded from the links below, they are long but not complicated.
For transmitter.
In recent years, radio-controlled car models have attracted more and more interest from both children and adults. These can be models on an electric motor or even on an internal combustion engine.
Within the framework of this article, we will reveal the topic of the device of various types of radio-controlled models, and consider the principle of their operation, so that those who are interested in designing their own radio-controlled models or simply buying them know what they have to deal with.
As for radio-controlled car models, first of all, you need to pay attention to the fact that the scales are very different, ranging from 1:5 to 1:28. The most popular scales today are 1:8 and 1:10, and as for the 1:5 scale, these are very large models, which are mainly ICE models. An internal combustion engine is larger than an electric motor.
According to the volume of cylinders, internal combustion engines are divided into classes: 12, 15, 18, 21, 25. These are numbers indicating the engine's displacement in cubic inches, in accordance with the American classification. Obviously, the higher the engine class, the higher its power. So, for example, the engine power of class 15 is on average 0.9 hp.
Internal combustion engines for radio-controlled models usually run on a mixture of oil, methanol and nitromethane. Such fuel in cans can be purchased at stores that sell radio-controlled models. Proprietary fuel is a guarantee of long-term operation of the motor.
Speaking of electric motors, it should be noted that they are usually powered by batteries collected in a battery, and the total battery voltage is 7.2 V or more.
Radio-controlled model stores sell such batteries, both in the form of individual 1.2 V cells, and in the form of ready-made batteries of various capacities. The motors themselves are classified by the number of turns of the stator winding, usually from 10 or more, and the fewer turns, the higher the rotor speed.
The basis of the model is the chassis, because it is on the chassis that both the engine itself and the electronics are located and attached. Chassis are of various types, with different modifications of drives, depending on the purpose of the model. Formula 1 cars are usually rear-wheel drive (more often) or all-wheel drive (less often) in order to develop high speed on a flat surface.
In buggies that drive on gravel, on sand, most often all-wheel drive, less often rear-wheel drive. Like buggies, trucks most often use four-wheel drive. Monsters with huge wheels, basically all-wheel drive. Road models, for driving on flat surfaces, more often with all-wheel drive.
When it comes to choosing between an electric motor or an internal combustion engine, it is important to compare all the advantages and disadvantages of both types of engines in order to make a rational choice.
So, liquid fuel models are capable of reaching tremendous speeds - up to 80 km / h, but think about the dangers of accidents, head-on collisions at such speeds. It is worth accidentally crashing into a wall, and expensive repairs will be required.
Will you pull regular gas stations with quality fuel, which is more expensive than gasoline? Although the engine size is small, and a 4-liter canister will last for a long time, but still. The advantage of the internal combustion engine is that the duration of the ride in time is quite significant, while the sound of the engine is very realistic. ICE models are more expensive than electric models.
From here you can see the main disadvantage of radio-controlled models on electric motors - they run out of battery pretty quickly, and riding on a single charge is unlikely to last more than a quarter of an hour. But models on electric motors, in comparison with models on internal combustion engines, drive very quietly, the engine is almost inaudible, there are no emissions, high acceleration, although the speed is low. However, you will have to fork out for a good battery and a charger in order to charge from the mains or from a car cigarette lighter.
In principle, the radio control of the models does not depend on the scale, it is installed on the model in the Ready to run format, if you buy the model, and does not require anything from the consumer except to pick up the remote control and start driving. However, some models are sold as a kit, and finally, someone will want to make a model themselves. Therefore, let's still consider the principle of operation of the radio control system.
Models with electric motors (as well as models with internal combustion engines) have a receiver installed. When the trigger is pressed on the remote control or the steering wheel is turned, the receiver inside the model immediately receives the signal sent from the remote control. The signal is processed in the receiver and the corresponding device in the model design is activated.
When you turn the steering wheel (on the remote), the servo will make the wheels turn through the rods. When you press the throttle trigger, the speed controller will receive a signal to change the engine speed, and through the transmission (cardan or belts), the wheels will begin to rotate faster or slower. The motor, as well as the receiver electronics with speed control, is battery powered.
If we talk about models with internal combustion engines, then when you press the gas trigger on the remote control, or when you turn the steering wheel on the remote control, a signal is still sent to the receiver. The receiver processes the signal and turns on the appropriate devices.
When you turn the steering wheel on the remote control, through the linkage system, the servomotor will make the wheels turn. When you press the gas, the second servomotor will move the carburetor damper, and the fuel-air mixture will be fed into the cylinder with a flow of a certain volume - the speed will change. A battery is used to power the servomotors.
So, as you understand, the design of a radio-controlled model includes the following integral components: a control panel, a receiver, servos, an engine (electric or internal combustion engine), and a speed controller for electric motors. These parts are sold as kits or individually.
Let us dwell in more detail on the principle of operation of the transmitter and receiver electronics. The transmitter is in its simplest form a high-frequency generator and a low-frequency modulator. The modulator turns on a high-frequency generator with the command frequency. Radiated by the console's antenna, a modulated high frequency signal is received by the receiver mounted on the model.
The receiver contains a low frequency amplifier, a high frequency stage and an electronic relay. The high-frequency stage amplifies and detects the received signal, then the signal is filtered, and the filtered signal is fed to the input of the low-frequency amplifier. The low frequency current of the command signal acts on the emitter follower, which leads to the operation of the relay in the power supply circuit of the corresponding motor.
In its simplest form, a radio-controlled model is able to drive forward and turn, this depends, of course, on the number of servos. So, a quadrocopter can have six drives.
As for commands, they can be transmitted over the radio, over wi-fi, over bluetooth, and over IR, due to the fact that the signal is always encoded after all and does not interfere, and the receiver easily recognizes its signal, thanks to presetting.
Now let's focus on batteries for models with an electric motor. Three types of batteries are common today: . A voltage of 7.2 V is typical for the first two types, and 7.4 volts for lithium. Lithium batteries are now becoming more and more popular, their capacity reaches tens of milliamp-hours, although the price, of course, is appropriate.
As for liquid fuels, here, as mentioned above, a special fuel is required that contains nitromethane. Nitromethane enhances the performance of the internal combustion engine, and the content of this component usually lies in the range of 16-25%. The oil in the fuel provides lubrication to the engine. The fuel canister indicates the percentage of nitromethane in the fuel, as well as the type of models for which this fuel is suitable.
The bodies are made of polycarbonate, a light and elastic material resistant to impacts. On sale there are models with a body and without. The body for your model can be purchased separately. Fortunately, the choice of bodies today is very large.
There are transparent and dyed options. Transparent ones can be painted from the inside with polycarbonate paint, such paint is sold in model stores. For beginners, a more elastic body is best, so that the control of an inexperienced driver would not lead to its rapid destruction from emergency impacts.