Interference-proof telecontrol system. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Radio control equipment

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On the pages of amateur radio literature, the units of discrete radio control of models [1, 2] have been described more than once, using various methods of command coding. The most acceptable for many practical cases is the digital method. However, such systems have insufficient protection against impulse noise.

As you know, the source of impulse interference can be not only lightning discharges, but also the executive engines of the model, as well as various equipment that is used in the national economy and medicine and operates at frequencies close to those used for telecontrol. These noises, getting to the input of the decoder, create a false signal at its output, and the model executes a false command.

The control system considered below has increased protection against impulse noise due to the special design of the decoder. It uses the number-pulse principle of commanding.

(click to enlarge)

Schematic diagram of the encoder is shown in fig. 1. A clock generator is assembled on the logic elements D01.1 and DD1.2. Its frequency depends on the resistance of the resistor R1 and the capacitance of the capacitor C1. Node DD2.1, DD2.2 - eight-bit shift register. Transistor - VT1 electronic key.

Let's consider the process of forming groups of impulses on the example of the "Stop" command. When the supply voltage is applied to the encoder, the clock generator generates a sequence of rectangular pulses with a frequency of 200 Hz and a duty cycle equal to two (Fig. 2, a). These pulses are simultaneously fed to the counting input

registers DD2.1 and DD2.2 and to the top input of the element DD1.3 according to the scheme. If the command buttons SB1-SB4 are in the position shown in the diagram, then pulses with a duration of 30 ms will appear at the lower input of this element (Fig. 2, b). At the output of the DD1.4 inverter, groups of pulses separated by a pause will be formed (Fig. 2, c). For the duration of the pulse, the transistor VT) opens, and the voltage from the power supply GB1 is supplied to the transmitter modulator.

When the power is turned off by switch SA1, capacitor C2 quickly discharges through resistor R2. If it is not discharged, then when the power is turned off, the voltage on it will decrease slowly and the transmitter antenna will radiate into space for some time not command groups, but a sequence of clock generator pulses. The work of the decoder will be broken.

It is easy to understand how groups of impulses of the remaining commands are formed by examining the table.

To avoid simultaneous submission of two or more commands by accidentally pressing several buttons, the encoder uses buttons with switching contacts [3].

For the correct operation of the protection device against interference impulses, it is necessary that, when moving from one command to another, the buttons SB1-SB4 are at least for a while in the unpressed position. In this case, after each command sent, the model will execute the "Stop" command.

Schematic diagram of the noise-proof decoder is shown in fig. 3. The decoder consists of a node that determines the pauses between the command groups of pulses - a single vibrator on the logic elements DD1.2, DD1.3; zeroing pulse shaper on elements DD1.4, DD2.1 and inverter DD2.2; counter DD3 of the number of command pulses in each group and node protection against interference pulses DD4, DD5, VD1-VD16, counting groups of command pulses. Register DD4.1 counts the groups of pulses of the command "Left", DD4.2 - "Right", DD5.1 ​​- "Forward" and DD5.2 - "Back". Diode VD17 prevents the negative pulses of noise generated by the motors of the model from passing through the power circuit. Capacitors C3, C4 reduce the voltage ripple that occurs during the operation of the model.

(click to enlarge)

Consider the operation of the decoder with the "Stop" command in the absence of interference. Let us assume that when power is supplied to the decoder, the counter DD3 and the registers DD4, DD5 are set to their initial state, i.e., the output 0 of the counter DD3 will be level 1, and all the outputs of the registers will be level 0. This state of the decoder is considered to be on duty, set after turning on the power of the model first, and after a while - the transmitter.

If now the first group of pulses of the "Stop" command (Fig. 1.1, a) is received at the input of the inverter DD4, then the front of the first pulse will start the one-shot and at its output (terminal 11 of the element DD1.4) level O will appear (Fig. 4, b). But the command pulses will also go to the counting input of the counter DD3. With each pulse of the group, a high level will move from one output of the counter DD3 to another in the direction of increasing their numbers, and information from the input D will be written to the first bits of the registers DD4, DOS in turn.

On the decline of the sixth pulse of the group, level 1 from the output 6 of the counter DD3 through the appropriate diodes will go to the installation input R of all registers and confirm their initial state. After a period of time equal to 6T (it is set by selecting the resistor R1), level 1 will appear at the output of the single vibrator, and a short pulse of negative polarity will form at the output of the reset pulse generation unit (pin 4 of the DD2.1 element) (Fig. 4, c). The pulse duration (about 0.25 ms) is set by selecting capacitor C2. From the output of the inverter DD2.2, a pulse (Fig. 4, d) will go to the input R of the counter 003 and set it to its initial state. Then the second, third, fourth, etc. groups will come to the input of the decoder, and the considered process will be repeated each time.

Now it will be easy to understand the operation of the decoder when receiving a command, for example, "Back" in the presence of interference. Each group of this command contains five clock pulses. Let us assume that groups of pulses with noise arrive at the input of the decoder - the first and third groups contain one noise pulse each, i.e., these groups will correspond to the groups of pulses of the "Stop" command.

In this case, at the end of the first group, register DD5.2 will remain in its original state. At the end of the second group, level 1 will appear at output 1 of this register, which, through the corresponding diodes, will go to the input R of the remaining registers and prohibit writing information to them at input D. After the third group, register DD5.2 will return to its original state, and at the inputs R of the remaining registers will be set to 0.

At the end of the fourth group of pulses, level 1 will appear again at output 5.2 of the DD1 register. Then, after the fifth, sixth and seventh groups, level 1 will appear at outputs 2, 3 and 4 of the DD5.2 register, respectively. As a result, the electronic key of the "Back" channel will work and the model will execute the command.

If now a group of impulses of the “Back” command with noise arrives at the decoder input, then all registers will return to their original state for a very short time - 37,5 ms, a logical zero level will appear at the “Back” output and the electronic key will close and reopen. Even if the actuator of the model has time to work for this time, this will practically not change the position of the model.

Consider another example - the passage of the "Forward" command, when groups of pulses with noise arrive at the input of the decoder. In each group of this command - four impulses. Let's assume that only one noise pulse was added to the first group of this command. Then the fifth pulse will transfer the registers to their original state and further recording will not occur in them. But since the second and subsequent groups of interference pulses do not contain, no command will appear on any of the outputs of the control voltage decoder (since writing to register DD5.1 ​​is prohibited) and then the operator will have to briefly release the "Forward" command button on the transmitter and click on it again. In other words, a false exit command will not work.

The encoder used capacitors K50-6 (C2), KM (O). Command buttons - KM1-1. Power source GB1 - battery "Krona". Capacitors in the decoder - K50-6. Diode D220A can be replaced with D220B, D311A, D311B.

When establishing the encoder, the resistor R1 is selected so that at a clock frequency of 200 Hz, the duty cycle of the pulses would be equal to two. By selecting the resistor R1 in the decoder, they make sure that the duration of the single vibrator signal is 6T. The current consumed by the encoder in the "Stop" command mode is not more than 3 mA, and by the decoder - not more than 5 mA.

The noise-immune telecontrol system described above is designed for five teams. However, it is not difficult to increase their number. To receive nine commands, it is necessary to use a twelve-bit shift register in the encoder and add four command buttons. In the decoder, it is necessary to use the free outputs of the counter 003, add the appropriate number of registers and diode-resistor nodes, and also set the duration of the output pulse of the one-shot equal to UT.

With the described decoder, you can use a ready-made tuned (or self-made) receiver from the Signal-1 transceiver kit. The transmitter can also be used from this kit. An improved version of this kit was published in the article by V. Borisov and A. Proskurin "Modified "Signal-1" in Radio", 1984, No. 6, pp. 50, 51.

Literature

1. V. Kozlov. Knots of equipment for controlling models. - Radio, 1983, No. 4, p. 24, 25.
2. V. Inozemtsev. Encoder and decoder of telecontrol commands. - Radio, 1985. No. 7, p. 40, 41.
3. S. Alekseev. Quasi-sensor switches on microcircuits. - Radio, 1984. No. 3, p. 26-29.

Author: A. Proskurin, Moscow; Publication: N. Bolshakov, rf.atnn.ru

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