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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Wireless remote control device Cyclops. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Clocks, timers, relays, load switches There are situations when you need to control equipment (TVs, VCRs) according to a specific program without the participation of an operator. This may be necessary, for example, in video surveillance systems. Conventional universal memory remotes for radio equipment are of little use here, since a certain sequence of actions is required, which depends on an external control signal. The proposed device performs this task. Recently, the circle of household video equipment (TV, VCR) has been replenished with new devices - door video cameras, cameras for monitoring a territory or an object, etc. This implies the need for a device capable of controlling the device on / off according to a given program, and preferably without altering them. One such device is shown below. It is designed for remote control of household television and video equipment as part of surveillance systems. With this device, you can automatically turn on the TV and VCR, this will simplify the use of the video eye and hidden cameras, as well as eliminate the need to purchase a monitor. "CYCLOPS" is a small device with a digital display, three control buttons, with an IR receiver window on the side and a remote IR emitter. The device can be placed in any place convenient for the user, and the IR emitter is attached to the wall or furniture opposite the TV and VCR. Scheme "of the device is shown in Fig. 1.
Let's start with a brief description of the principle of transmitting commands from remote controls for household equipment. There are several ways to encode information for transmission over the IR channel. The first is high frequency modulation. A carrier frequency close to 43,5 kHz is modulated with a relatively low-frequency information package. This allows you to get rid of the constant component of the infrared background of the room. The second way - the command is presented in the form of the "MANCHESTER" code, which does not have long zero or single states and is therefore well protected from interference. Some manufacturers use the one-time code transmission method to conserve the battery life of the remote control. When you press a key on the remote control, a packet with the command code is first transmitted, and then relatively short parcels with the code of holding the pressed key follow. The task of the device is to receive and decode commands, write them to non-volatile memory, and then, having received a signal from the outside, broadcast these commands in a certain sequence. The quality of work largely depends on the accuracy of receiving commands. Module BL1 - a standard single-chip photodetector from a color TV - is designed to enter commands from the remote control. From the output of the module, the inerted digital sequence, cleared of the constant component, is fed to the input P3.2 of the microcontroller DD1. It is better to use a ready-made photodetector, since rather high requirements are imposed on it in this device. Photodetectors of various types are now on sale in stores. The processed information about the received commands in a special form is stored in the DS1 ROM. The generated code sequence from the output P1.0 of the controller DD1 is fed to the input of the element DD2.4, which together with DD2.3 forms a pulse generator with a repetition period of 27,2 μs. This parameter must be maintained as accurately as possible, since most single-chip photodetectors, household equipment for receiving commands from remote controls are unified and have the same carrier frequency parameters. From the output of the element DD2.4, the code sequence is fed to the current amplifier - transistor VT2. The transistor is loaded with two IR emitter diodes BI1 and BI2. They also manage the video equipment itself. Diodes of different types - AL156A and AL145A - were not chosen by chance. The fact is that the wavelength of radiation from remote control panels of different television and video equipment from different manufacturers may vary. Therefore, two different diodes are used to get a wider emission spectrum. If there is not enough power (this happens when the equipment is located in different places), you can increase the number of LEDs by choosing a resistor R15. The CYCLOP device has two universal inputs. Input 1 - with galvanic isolation on optocoupler U1 - is designed for an input DC voltage of 12 V, but if it is connected through a quenching capacitor, then it can also work from a ~ 220 V network (for example, connect a house bell). Input 2 is the input of the Schmitt trigger, assembled on the transistor VT1 and element DD2.2. This input can be used for both 12 V and any analog signal from a microphone amplifier or audio intercom. The signals from both inputs pass through a digital filter, the transmission coefficient of which is set by software. Both inputs are capable of triggering on any edge, allowing the device to be used with a variety of sensors. The device is assembled on a printed circuit board (Fig. 2) from one-sided foil fiberglass 1,5 mm thick. Resistors R17-R32 - R1-12 or others for surface mounting (they are soldered to the printed circuit board from the side of the conductors). If there are no surface mount resistors, you can drill holes and mount conventional MLT 0,125 vertically. The digital LED indicator HG1 (King Bright) is soldered to the board from the print side over the resistors R23, R24, R31, R32. In addition, it is located points up. The control buttons are also located on the print side. Stabilizer DA1 is screwed to the board, the foil under it acts as a heat sink.
The program is written taking into account the fact that the frequency of the master oscillator is 24 MHz. By the way, you can use a quartz resonator for a different frequency - from 10 MHz or more. IR photodetector BL1 - from TVs and VCRs Funai, Samsung, LG. Throttle L1 - DM-0,1. The DD1 microcontroller (ATMEL) is installed in a panel soldered to the board. When programming the device, the connecting wires should be as short as possible in order to reduce the effect of interference. It is desirable to close the photodetector window with a light filter that transmits only IR rays. The remote control should be placed at a distance of 10...60 cm from the device. Commands from the remote control of the TV or tape recorder are entered into the memory of the device. On command from the external sensor of the call button, the device will execute the specified program: turn on or switch the TV and VCR. The control panel has three buttons and a display. The user can select different options using the buttons. The device memory is divided into 16 sections (programs), each of which can consist of 16 steps (hardware control commands). For normal and efficient operation of the device in the video surveillance system, it is necessary to correctly enter the program into memory. To better understand the principle of programming, consider an example. Let's say, on a doorbell call, you need to turn on the TV for 15 seconds, then turn it off, and turn on the VCR for recording for 30 seconds and then turn it off too. Since some TVs are not immediately capable of receiving commands from the remote control after switching on, you must wait 5 seconds before turning on the TV's video input (AV) to which the video eye is connected. Imagine how you can perform these operations using the TV and VCR remotes.
And now let's try to translate this control algorithm into a program for the CYCLOP device.
You need to be very careful when designing your program. The considered example does not take into account all the features of the operation of the surveillance system, and household equipment often works according to different algorithms, with different response times. The device has five modes of operation. MODE "PROGRAM" - PROGRAMMING The "PROGRAM" mode is turned on by pressing the SB1 "Mode" button. The display will show '00 (a leading dot indicates programming is on). If the programs have already been entered and some of them need to be corrected, it is selected using the SB2 "<<<" or SB3 ">>>" buttons. The character in the first familiarity of the display is the number of the program being dialed in hexadecimal code (0 - first, F - sixteenth), and in the second - the ordinal number of the step (command) in the program, also in hexadecimal code. Pay attention to the type of control panel used. The fact is that in remote control systems several types of commands are used. Differences in working with a TV or VCR may not be visible at all, however, these commands are entered into the CYCLOP device in different ways. For simple commands (without power saving) everything is simple: one click - one command. When entering commands of a different type, it will be necessary to make three clicks on the same button on the remote control so that the "CYCLOPS" understands the transmitted command. The difference will be visible immediately on the operation of the device. Until the command is reliably determined, there will be no transition to the next step! Having determined the command, the device proceeds to the next programming step - the number on the display will increase by one. Now you can enter the pause time between commands or the next command into the program. The pause time is dialed with the "<<<" or ">>>" buttons, it can be changed from 1 to 256 s. Each press adds a delay of 1 s, the total time in seconds the display shows in hexadecimal code. Each time these buttons are pressed, the display will indicate for approximately one second the duration of the delay that will be executed AFTER the command just given. By default, it has the minimum possible value - 1s. After setting all the steps of the program by pressing the SB1 "Mode" button, you can interrupt the programming and use the SB2 and SB3 buttons to select the next program to enter. Pressing the "Mode" button again will cause the device to switch to the "WORK" mode (this will be discussed below). If during programming a command that has already been entered earlier is entered, it is not allocated a separate place in memory, and only its number is placed in the program. You can distinguish between the initial and repeated introduction of a command as follows: during the initial input, when the device does not identify it with any of the commands already in memory, a dot appears on the indicator in the second familiarity of the display ('0'0) and remains until releasing the remote control button; in the same case, if the device finds the command being entered among those already stored in memory, the dot does not appear in the second familiarity. This feature is useful for determining whether a device is capturing a code. If you repeatedly enter the same command and all attempts or some of them, except for the first, are accompanied by the appearance of a dot in the second familiarity, then the code is determined uncertainly. You should choose the distance between the device and the remote control or get rid of the excessive infrared background in the apartment (say, draw the curtains if the sun is shining brightly in the yard). It is worth noting here that sometimes there are remotes that, when you press the same button twice, generate codes that are slightly different from one another. For example, the remote control of one of the SAMSUNG TVs, with each odd press, gave the last bit equal to one, while for each even this bit was equal to zero. This feature does not affect the operation of the device. "TEST" MODE The "TEST" mode is intended for debugging and checking the program. It consists of two sections: checking commands and programs. You can enter these modes from the programming mode. By pressing the buttons SB2 and SB1 at the same time, the display will show L0. The symbol L means checking the command, and the number 0 indicates its number - the first one. You can select the command to be checked using the SB2 and SB3 buttons. When you press the SB1 button, the device will play the selected command. When you press the buttons SB3 and SB1 at the same time, the display will show NO. In this mode, you can check the whole program. You can select the program to be checked using the SB2 and SB3 buttons. When you press the SB1 button, the device will play the selected program. Thus, you can check the operation of each individual command and the program as a whole. If at least one command fails, it is necessary to reprogram the device more carefully. If an error is found in the execution of the program, it will be possible to return to the "PROGRAM" mode and reprogram only it. You can exit the "TEST" mode by pressing again the same buttons that were pressed when entering. WORK MODE The "WORK" mode is the main one. The user can choose the number of the program recorded in the memory, according to which the device will work. Examples of display readings in the "WORK" mode: flashing characters 10 or 3- or 04. This is the waiting mode for a pulse from any input. The first digit shows the number of the program that will be started from input 1, and the second digit shows the number of the program that will be started from input 2. If the display shows a dash instead of a number, this means that the corresponding input is disabled and the device will not respond to the impulse. When two dashes flash on the display, both inputs are disabled and "CYCLOPS" will not execute any program. You can select a program for each input using the SB2 and SB3 buttons. If within a certain time the input pulse is not received, the display turns off, and the device continues to work in the "WORK" mode without indication. This function is needed so that the display does not attract undue attention. The display can be turned on by pressing the SB2 or SB3 button. The time interval before the display turns off is set in the device parameters. ACTIVE MODE If the device is in "WORK" mode and any of its inputs, for which a program is defined, receives a pulse, it goes into "ACTIVE" mode. The pulse duration must exceed a certain value (parameter P0 or P1 in the parameters section). This is necessary to prevent false alarms of the device from short pulses that may appear as a result of interference penetration. Immediately after switching to the "ACTIVE" mode, the CYCLOP starts executing the program defined for this input. The display shows a special symbol in the form of three horizontal lines and the number of the command being transmitted. At this time, the device is not able to perceive button presses or repeated input pulses. After finishing the program, the device will return to the "WORK" mode. PARAMETER MODE This mode is required only during device programming. You can enter it from the programming mode by simultaneously pressing the buttons SB2 and SB3. We list the parameters that can be set in this mode.
Parameters RO and P1 are set in hundredths of a second and, accordingly, can take values from 0,01 to 2,56 s. Setting the parameters RO or P1 equal to zero ensures that the device is triggered by the first change in the signal level. The active level for inputs is the level opposite to that which was available at the input at the moment the device switched to the "WORK" mode. If it is necessary to apply an alternating voltage with a frequency of 2 Hz to input 50, then the parameter P1 must be set equal to zero, since in this case the input will have a pulsating voltage with a frequency of 50 Hz and a duration of less than 0,01 s. Parameter P2 sets the number of sending the command code when the device executes each step of the program. This parameter is needed in situations where the controlled object (TV or VCR) is uncertain about sending commands. Usually a value of 2-3 is sufficient. The meaning of parameter P3 is the interval between sending commands in a burst, expressed as a percentage of the length of the command (its duration in time). It was introduced just in case, since the "proprietary" interval between commands from the remote control is not measured and is not recorded in memory. Practice has shown almost complete non-criticality of this parameter within the specified adjustment limits. Parameter P4 is changed in the case of using a quartz resonator with a frequency different from that indicated in the diagram. This parameter is used solely for the correct generation of time intervals between commands and guard intervals. Do not forget that the lower the clock frequency, the worse the accuracy of recording and playback of commands. The default frequency of the quartz resonator is 24 MHz. Parameters P6 and P7 are for reference, they reflect the numbers of programs assigned to inputs 1 and 2, respectively. In "PARAMETER" mode, they cannot be changed. Parameter P8 defines the time in seconds between the last button press and the display turning off. During programming, "CYCLOPS" may indicate errors. Almost all errors are reset automatically. Here is their description:
If the device memory is full, it is necessary to perform an erase operation. To do this, enter the "PROGRAM" mode and press all three buttons at once. The display will show flashing characters in the form of three horizontal lines. Without releasing the buttons, you need to wait for the dashes to appear, while all information in the memory of commands and programs will be erased. Device settings remain unchanged. Software for the microcontroller Authors: D.Bespyatykh, A.Kolesnikov, Pervouralsk, Sverdlovsk region.
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