At present, many devices controlled by the GSM (Global System for Mobile Communication) standard are already being produced industrially - a digital standard for mobile communications or a mobile phone that is now familiar to everyone. These are various control cabinets for industrial equipment, or even just individual sockets, as shown in Figure 1.
The design looks like a regular adapter that plugs into a wall outlet. The load can be switched on by calling or sending sms via mobile phone. Manual control is also possible using two buttons located on the front panel. The power switched by such sockets, depending on the model, is in the range of 1 - 5 kW, which allows you to turn on almost any load.
Multi-channel sockets are also produced, like a computer “bast shoes”, which allow you to independently control the operation of several loads. Such devices are one of the, and therefore, their price is quite high: if you search on the Internet, then prices range from 1000 to 3500 or more rubles.
Picture 1. Remote module sms management
For example, a socket with a remote control via sms (can be controlled by 5 users) with a built-in temperature sensor. With the help of a sensor, the socket can automatically turn off and turn off household appliances in accordance with the ambient temperature:
Figure 2. Socket outlet with remote control sms
Even more expensive than individual sockets are industrial modules. As an example, Figure 2 shows an offer from an online store for the sale of a DTMF control module.
Figure 3
It was from this drawing that the abbreviation DTMF, which is still incomprehensible, appeared on the surface. Let's see what it is below.
DTMF signals
In old phones, dialing was done by rotating the disk: the dialer spring was wound up with a finger for the required number of digits, the disk was spinning back, closing the contact, and clicks were heard in the handset. Such a set was called impulse. Pulse dialing was also used in modern push-button telephones.
Currently, the so-called tone dialing is used. Try to dial a number on a landline phone - sounds of different tonalities are heard in the handset. It listens to DTMF signals, - Dual-Tone Multi-Frequency, - two-tone multi-frequency signal. Figure 4 shows a table that forms the numbers and some characters transmitted when dialing a number.
Figure 4
For example, the number "1" corresponds to a combination of frequencies 697 and 1209 Hz, and the number "9" corresponds to 852 and 1477 Hz. Frequencies are selected in such a way that when transmitted together, they do not form harmonics. To decrypt tonal bursts, there are specialized microcircuits - decoders, for example IL9270N, HM9270, MT8870. They are just different companies. They may even differ in the number of pins, or, as now in a foreign manner, pins (from the English pin), but they perform the same functions.
In addition to these specialized decoders, DTMF signals can be decoded on digital computers using the Herzel algorithm. Naturally, these signals can also be decoded using microcontrollers or, as they are sometimes called, embedded computers.
In addition to dialing a DTMF telephone number, the technology is widely used in smart home systems, alarm and burglar alarms. DTMF tags are also used in commercial broadcasting.
The DTMF system was developed back in 1961, but reached Russia only in the nineties of the last century. At first, tone dialing was provided as a paid service, and even then not everywhere, since tone dialing is possible only at modern digital telephone exchanges. In general, antediluvian relay stations are still in operation in many places, which allow you to use only pulse dialing.
And now, try to do this experiment: call on a cell phone, well, at least to your work colleague, because you are in the same room all day. After he “picks up the phone”, press any numbers on your phone: DTMF signals in the form of short musical sounds will be heard in the speaker of his phone. (According to the laws of physics, sounds that have a certain frequency are called musical). For example, the noise on the street cannot be considered a musical sound.
The same sounds are also present in the speaker of the telephone headset: the matter is small - just plug the DTMF decoder into the headset jack and here you are, the finished control device. In some cases, the number of managed loads is just one, and it is required to turn it on or off at any time.
Homemade remote devicestelephone control
A few words about the operation of the scheme. The basis of the device is a polarized relay. As can be seen from the diagram, it has two coils connected in such a way that when voltage is applied to one coil, the relay armature is attracted to one core, and remains in this position even if there is no longer voltage on the coil - there is a magnet inside the relay.
In order to snap the armature into the opposite position, it is required to apply voltage, at least a pulse of sufficient duration and amplitude, to another coil. The armature will remain in the attracted state, even when the supply voltage is removed. Isn't it very reminiscent?
The device is powered from the mains, through a half-wave rectifier D1, R1, R2, C1. Capacitor C1 produces a voltage of about 24V. Of course, this is done in violation of all safety rules, but the author assures that if you don’t get too impudent and don’t go where you don’t need to, then ... Well, in general, everything will work out!
The phone must have a vibrating alert: it is to its contacts that the optocoupler relay IC1 will be connected, in the diagram it is the resistor R4 and the output of the optocoupler 1. The polarity of the connection is indicated in the figure. When connected to the phone, the polarity of the voltage on the vibrating alert should be checked using a multimeter or an LED with a resistor.
When the vibration is triggered, the output transistor opens inside the optocoupler (pins 5 and 6). Capacitor C4 is charged from the power supply through the right winding of the relay and the open transistor of the optocoupler. The armature of the relay switches to the left coil, and with contact K1.2 it turns on, and with contact K1.1 it prepares the left coil for the next switching.
Capacitor C4 is discharged through resistor R3 for about five minutes, during which time the status of the device will not be changed from the phone. With all the obvious simplicity, the device has one significant drawback: the ability to get an exotic polarized relay, and even the right passport, is now practically zero. Even the author of the scheme himself writes about this in his description.
Another simple control device is shown in Figure 5.
Figure 5.
Made on a specialized chip - signal decoder DTMFMT8870. The purpose of this device in the author's performance is to remotely turn on and restart the computer. The device works as follows. After you have called this number, dial 1 or 2 after picking up the handset, which corresponds to turning on the computer "POWER" or rebooting "RESET".
The circuit is powered directly from the cell phone, the output transistors of the optocouplers are connected in parallel with the corresponding computer buttons. PC817 optocouplers are widely used in switching power supplies, from computers to mobile phone chargers.
The device is connected to the headset jack, to the speaker outputs, on which, as described above, DTMF signals appear. The main problem with this scheme, when repeated, is that the phone, when a headset is connected, must auto-pick up the handset. But not all phones have this option.
Figure 6.
The circuit is implemented in hardware, i.e. does not contain microcontrollers that require software, all the logic of operation is achieved through the circuit itself.
The phone call is received by a microphone, amplified to the desired level by an amplifier, as a result of which a relay is activated, the contacts of which are connected to the Answer button (hook up). After this relay trips, a time delay of about 7 seconds starts. If during this time you have time to press the necessary keys, then the DTMF signal will be sent to the DA1 decoder, the output signals of which through the DD3 decoder through the relay can connect - disconnect up to 12 loads.
After 7 seconds, the “Hang up” relay will work (its contacts are connected to the “hang up” button), for subsequent control, one more call will be required. Thus, it turns out that the phone will simply be wrapped with wires: wires from the relay to the buttons, and even the DTMF signal output from the headset jack.
A simpler scheme, meaning by the number of parts, is shown in Figure 7.
Figure 7. Scheme of the load control device by phone (click on the picture to enlarge)
This is where the phone with auto-hookup is used with a headset connected, so you don’t need to solder to the buttons, you just need to connect the headset jack. This circuit provides control of 8 loads, the control commands are shown in the description of the circuit.
But these schemes are not at all those that were called the most complex and serious at the beginning of the article. There are those who use an embedded SIM300D GSM module instead of an old cell phone. Its price is 4200 rubles, although it has already been discontinued. It is in this module that the SIM card is inserted.
For more information on how to independently assemble and program a remote control device in the author's development, read here:
Step-by-step instructions on how to independently assemble and configure a load control device on a mobile phone -
Schematic diagram of a set-top box for a cell phone for remote control and monitoring of the load status, not a complicated circuit on the KR1008Vzh18, K561LA7 microcircuits. There have already been several articles on the pages of the Radioconstructor magazine on the topic of remote control using a cell phone.
Usually, this is taken from a cell phone with an auto-answer mode. And from it the signal is fed through the headset to the DTMF decoder. Next up is the relay. With all the advantages, such a scheme also has an important drawback - it is not known what state the load is in, that is, it is on or off.
After all, we do not see what we control, and situations can be very different, for example, a power outage, or for another reason, the switched on load may not turn on or turn off if it is turned off.
circuit diagram
In this scheme, a solution to this problem is proposed - during the on state of the load, a repeating single-tone sound signal is applied to the microphone input of the cell phone headset, repeating at a frequency of about 0.3 Hz. That is, every three seconds. To determine the load is currently on or off, you need to call the object and listen. If there is a repetitive sound, the load is on; if it is not there, it is off.
The repetition period is chosen so large (3 seconds) that it is possible to give a command to turn off in the pause of the sound signal so that the sound does not interfere with the control. The device allows using a cell phone to control one load, switched on by an electromagnetic relay.
Rice. 1. Principal diagram of the set-top box for remote control and monitoring using a cell phone.
The diagram shows a standard headset with two earpieces, a microphone, and a button to control a cell phone. Now, most of the inexpensive cell phones come with just such headsets. When a headset is connected, the phone enters headset mode. When a call comes in, it vibrates, the display lights up, and a call tone is heard in the headphones.
You need to first transfer the phone to auto answer mode, this can be done in the settings for working with the headset, referred to in different phones - “car”, “hands free”, “auto answer”, “answer mode - automatically” or otherwise. In this mode, the phone itself will “pick up the phone” when any incoming call arrives.
Auto answer mode is available on most cell phones with wired headset jacks. However, there are those in which this mode is not available, despite the presence of a wired headset. This needs to be checked first. And so, an incoming call comes in, and the cell phone, being in auto-answer mode, “picks up the phone”.
After the incoming call is accepted, the DTMF decoder circuit on the D2 chip comes into operation. Since you will need to manage by pressing the buttons of the cell phone from which the call came. In this case, the tone code of these buttons will be transmitted, and through the headset it will go to the decoder on the D2 chip.
The RF signal is input to the D2 chip through C4-R4. The gain of the input ultrasonic microcircuit depends on the resistance of the resistor R4. When establishing, through trial and error, using this resistor, you need to set the optimal sensitivity of the D2 chip.
To give a command, you need to press one of the numeric buttons on your cell phone. In this case, to turn on relay K1, you need to press the button "1". To turn off - the button "2" (or another).
If a two-tone DTMF signal arrives at the input, the signal is decoded and as a result, a command binary code appears on pins 11-13. If the "1" button was pressed, then the unit will be at pin 11. A logical unit occurs, and the key on the transistor VT1 will open. Relay K1 included in its collector circuit with its contacts (not shown in the diagram) will turn on the load.
To indicate the on state, a repeating sound signal generator is assembled on the D1 chip. It consists of two multivibrators. The multivibrator on the logic elements D1.1 and D1.2 generates pulses with a frequency of about 0.3 Hz. These pulses are fed to pin 8 of element D1.3, which is part of the second multivibrator that generates pulses with a frequency of about 2.5 kHz.
When relay K1 is turned on, there is a logic one at pin 11 of D2. It goes to pin 2 D1.1 and starts the repeating sound signal generator. A repetitive sound signal through the resistor R3, which, when adjusted, sets the optimal signal level, is fed to the microphone input of the headset.
And the user hears a repeating beep as confirmation that the load is on. When the load is off, there is a logic zero at pin 11 D2. It goes to pin 2 D1.1 and turns off the repeating beep generator. And the user does not hear a repeated beep, which is a confirmation that the load is turned off.
Pin 10 of the D2 chip is connected to the positive of the power source, so after each command is received, the relay state will be maintained until the next command arrives. Relay type WJ118-1C or can be replaced by some other low-powered one with a winding of 12V and a winding resistance of at least 200 Ohms, and make contacts.
Myasnikov S. V. RK-2017-01.
Literature: 1. Myasnikov SV - The answering machine opens the gate. RK-7-2015.
A friend of mine turned to me with such a request: they say, I want the garage to turn on the fireplace on a call from a cell phone. He has a workshop there, and it’s cold in the mornings, so he wants to turn on the fireplace two or three hours before he arrives. Everything is very simple: he turns on the fireplace by phone, and in two hours, if he does not come, the fireplace will simply turn off by itself.
Talk about making it easier if you buy a programmable relay did not convince him. Apparently, he could not appear there on some days, and this, when programming the relay, could not be taken into account. And the counter would have been spinning there while the fireplace warmed the empty room.
At present, many devices controlled by the GSM (Global System for Mobile Communication) standard are already being produced industrially - a digital standard for mobile communications or a mobile phone that is now familiar to everyone. These are various control cabinets for industrial equipment, or even just individual sockets.
Naturally, my friend simply did not have that kind of money, and the phone was already lying around idle. Yes, apparently, he is not the only one, if a sufficient number of schemes are posted on the Internet, ranging from the simplest single-channel to the most complex and serious, managing several channels.
So I was asked to do a device to turn on the fireplace in the garage using a cell phone. To get acquainted with the issue, a number of similar schemes were viewed (what if something just happens to be repeated by someone else, already finished).
Some schemes were redundant, because it was about managing only one load, and not eight or at least four. They also scared away schemes containing a large number of details. Others demanded a phone with auto-hook when connected to the headset jack.
One circuit contained only one transistor with a sensor in the form of an inductor and a microcontroller. The microcontroller in that circuit seemed to act only as a digital filter, protecting it from false positives from interference.
The purpose of the scheme was simply to restart the remote computer - the server. When it hung, they simply pressed a button on the phone, the computer rebooted and continued to work. It was decided to go approximately in this way, namely, to receive a signal from the phone in a similar way, without getting tangled in the wires, without connecting to the phone.
Actually, any scheme has its advantages and disadvantages, so you should not think that the development of your own scheme was the result of rather seditious thoughts: “They say they invented it, don’t understand what, but everything turns out to be so simple and my scheme will be better than everyone else’s.” Not at all, there were no such thoughts, it was simply decided to make a device from what was already available.
After several experiments with an inductive sensor (before the ringing tone, the phone emits impulses that immediately turn on the device), it was decided to use just a microphone from the telephone, since the faulty device was at hand.
The control algorithm is simple: having received a call on a cell phone, the device simply turns on the fireplace, and after two or three hours it simply turns it off. In this case, it is possible to re-enable by calling from the phone when everything is already turned off. A condenser microphone was used as a call sensor.
The article in which I describe in detail the composition of the device and the operation of the fireplace control circuit by telephone turned out to be large, but interesting. In this regard, I decided to issue it in the form of a small practical guide (step by step instructions) in the format of an e-book.
You can download step-by-step instructions on how to independently assemble and configure a load control device by cell phone at this link:
I will be glad if this e-book is useful to you!
Boris Aladyshkin
Hi all.
Do you want to control something on a cell phone, and even without any abstruse microcontrollers? If yes, welcome under cat.
Recently, there have been several reviews of GSM modules on Muska, such as SIM800, using which you can control anything over a cellular network. But the trouble is, they all require connecting to a microcontroller, writing firmware and other things that are difficult for an uninitiated person. The other extreme is: “and I soldered a relay to the vibration motor of the phone, everything works for me” :)) This is also possible, but do not be surprised if your greenhouse will try to water the pump with water from a frozen well, after the SMS message “With the New Year!" from unknown sender
In general, I decided to fill the gap between these two solutions, and offer my own.
Today we will talk about a DTMF signal decoder, or, in a simple way, a tone signal.
The curious can read
The technology is quite outdated, but is still supported by all phones.
Actually, it is tone dialing that you use when you call some institution, and the answering machine tells you: “if you know the subscriber's number, press“ 1 ”, if you want to know about our new offers, press“ 2 "and so on. By pressing the button with the desired number on the phone, you send a signal of a certain tone over the voice channel. Each character on the phone keypad has its own “melody”. It is this sound that the DTMF decoder decodes, turning it into signals at its outputs. 
The board is assembled on a microcircuit, powered by 5 volts and has the following outputs: Q1-Q4-discrete outputs, StQ/StQ inverted-outputs that are triggered every time a signal is recognized correctly. Audio IN if you don't want to use the soldered 3.5mm jack. GND/VCC supply, 5 volts.
Outputs Q1-Q4 operate according to the table: 
For example, now I have two middle LEDs on the board, the outputs Q2 and Q3 have worked, we look at the table - this corresponds to the pressed “6” key. If I press the "1" key, then the output Q1 will work, if "2", then Q2. If "3", then the outputs Q1 and Q2 will "light up" at the same time. And so on.
In general, this is a 4-bit code. If you decrypt it with a special microcircuit, you can get 16 outputs.
By the way, Ali sells a board already with a decoder, but it costs more. An option for the advanced is to connect all this to the microcontroller, I did this, you can even set a password - I called, dialed the password, got access to control ...
But this is no longer within the scope of my article, because. At the beginning of the article, I promised that everything would be simple.
And so, we take the KT815 transistor, a 1.1 kΩ resistor, or so, a 12 V relay, and an LM7805 stabilizer. The remaining parts (protective diode 1N4007 on the relay coil, yellow ceramic capacitors 0.1 microfarads and electrolytic 1000 microfarads) are desirable, but it works without them. A tweeter is connected to the relay as a load.
I won’t draw a diagram, the installation is hinged, everything can be seen in the photo: 
On the other side: 
The total power supply of the structure is 12 V, because this is required by the relay, but for the board it is reduced by the stabilizer to 5 V.
We connect the 3.5 mm jack on the board with a cord to the headphone output of the phone, set up auto-pickup of the handset and you're done. Now, if you call the phone connected to the board, wait until the handset is off, press "1", the relay will work, the buzzer will start beeping. If you press "2", everything will turn off. By the way, no matter what you plan to control, I would recommend leaving the buzzer. This is convenient, because you can hear it on the phone, and in this way you can get some kind of feedback: you called, you hear a beep, which means the load is on :)
Made a short video showing how it all works.
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The device is intended for remote control of loads via telephone line or GSM channels. It connects to a telephone line or to a cell phone that supports AT command control (eg Siemens C35). The circuit diagram shows, and the printed circuit board provides elements for the subsequent modernization of the device and ensuring its compatibility with any firmware versions. The schematic diagram is shown in the figure. In a higher quality resolution and in ssd * format, as well as a printed circuit board and microcontroller firmware can be downloaded from the link at the end of this page.
Programming mode. Connect the device in parallel with a telephone connected to the telephone line and in tone mode. Instead of a telephone, you can use any source of DTMF signals - in this case, they must be fed to the DTMF input. Press and hold the PROG button for more than 2 seconds. At the same time, the LED will light up. Enter a four-digit password. The entry of each digit is confirmed by a beep. The fifth digit determines the number of calls before "auto pickup" - i.e. device activation. After entering the number of calls, the device automatically exits the programming mode.
User mode. Dial the phone number to which the remote control is connected. If dialing is done from a fixed telephone, it must be in tone mode. It is also possible to dial a number in pulse mode, however, after dialing a number, you must switch to tone mode to enter a password and control loads. Also, control is possible from any cell phone. After passing the number of calls programmed by the user, the device will connect to the line (GSM channel) and the user must enter a four-digit password. If the password is entered incorrectly, the device will turn off. If the input is correct, the user enters the load management menu. Buttons 1-4 select the appropriate load channel. Then pressing the symbol "*" the device turns on. To turn off, the desired channel is again selected and the “#” symbol is pressed. When channel 5 is selected, all loads are controlled simultaneously. After finishing work, you must double-click the "#" symbol. In this case, the device is disconnected from the line and returns to its original state. It is also provided for disconnection from the line at the timer command if there were no commands from the operator for more than one minute
Sound alarm
The execution of a certain command is confirmed by an audible alarm or an informational voice message (depending on the firmware of the microcontroller)
Firmware version 1.0
Programming Input Confirmation - High Frequency Double Tone
Password prompt - high frequency triple tone
Password Verification - Triple High Tone
Password Invalid - Low Frequency Triple Tone
Correct channel selection (1-5) - high frequency single tone
Wrong channel selection - single low frequency tone
Load on - high frequency double tone
Load disconnected - low frequency double tone
End of work - low frequency triple tone