DIY smart GSM socket. The principle of operation and how to make a GSM socket yourself Do-it-yourself switch from a phone

Currently, many different devices are already being produced industrially, controlled according to the GSM (Global System for Mobile Communication) standard - the digital standard for mobile communications or the now familiar mobile phone. These are various control cabinets for industrial equipment, or even just separate sockets, as shown in Figure 1.

The design looks like a regular adapter that is inserted into a wall outlet. The load can be activated by making a call or sending an 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, similar to a computer laptop, which allow you to independently control the operation of several loads. Such devices are one of the devices, and therefore their price is quite high: if you search on the Internet, prices range from 1000 to 3500 or more rubles.

Figure 1. Remote module sms control

For example, a socket with remote control via SMS (can be controlled by 5 users) with a built-in temperature sensor. Using a sensor, the socket can automatically turn household appliances on and off according to the ambient temperature:

Figure 2. Socket with SMS remote control

Industrial modules are even more expensive than individual sockets. As an example, Figure 2 shows an offer from an online store to sell a DTMF control module.

Figure 3.

It was from this drawing that the still incomprehensible abbreviation DTMF appeared on the surface. Let's see what it is below.

DTMF signals

In old phones, dialing was done by rotating the dial: your finger wound the dial spring to the required number of digits, the dial spun back, closing the contact, and clicks were heard in the handset. This set was called impulse. Pulse dialing was also used in modern devices with push-button dialers.

Currently, the so-called tone dialing is used. Try dialing a number on a landline phone; you can hear sounds of different tones on the receiver. This is listening 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 of 697 and 1209 Hz, and the number “9” corresponds to 852 and 1477 Hz. The frequencies are selected in such a way that, when transmitted together, they do not form harmonics. To decrypt tone messages, there are specialized chips - decoders, for example IL9270N, HM9270, MT8870. These are simply analogues of different companies. They may even differ in the number of pins, or as now in the foreign style of pins (from the English pin), but they perform the same functions.

In addition to these specialized decoders, DTMF signals can be decrypted on digital computers using the Goertzel algorithm. Naturally, these signals can also be decrypted using microcontrollers or, as they are sometimes called, embedded computers.

In addition to dialing a telephone number, DTMF technology is widely used in smart home systems, alarm and security alarms. DTMF marks are also used in commercial radio 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 not everywhere, since tone dialing is only possible at modern digital telephone exchanges. In general, in many places there are still antediluvian relay stations in use that only allow the use of pulse dialing.

Now, try this experiment: call on your cell phone, or at least 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 will be heard in the speaker of his phone in the form of short musical sounds. (According to the laws of physics, sounds that have a certain frequency are called musical). For example, noise on the street cannot be considered a musical sound.

The same sounds are also present in the dynamics of a telephone headset: all that’s left is to simply connect a DTMF decoder to the headset connector and there you have it, a ready-made control device. In some cases, the number of controlled loads is only one, and it needs to be turned on or off at any time.

Homemade remote devicesphone control

A few words about the operation of the circuit. 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 reverse position, it is necessary to apply voltage, at least a pulse of sufficient duration and amplitude, to another coil. The armature will remain attracted, even when the supply voltage is removed. Isn't it very reminiscent?

The device is powered from the network 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 shouldn’t, then... Well, in general, everything will work out!

The phone must have a vibration alert: it is to its contacts that the optocoupler relay IC1 will be connected, in the diagram this is resistor R4 and optocoupler output 1. The polarity of the connection is indicated in the figure. When connecting to a phone, the polarity of the voltage on the vibration 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 source through the right relay winding and the open optocoupler transistor. The relay armature 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 messages from the phone will not change the state of the device. Despite all its obvious simplicity, the device has one significant drawback: the ability to get an exotic polarized relay, and even the necessary 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 its original design is to remotely turn on and restart the computer. The device works as follows. After you have called this number, after picking up the handset, dial 1 or 2, which corresponds to turning on the computer “POWER” or rebooting “RESET”.

The circuit receives power directly from the cell phone, the output transistors of the optocouplers are connected in parallel to 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 terminals, on which, as described above, DTMF signals appear. The main problem with this scheme when repeated is that the phone must auto-pick up the handset when a headset is connected. 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 operating logic is achieved through the circuit itself.

The telephone call is received by a microphone, amplified to the required level by an amplifier, as a result of which a relay is activated, the contacts of which are connected to the “Answer” button (pick up the handset). After activation of this relay, a time delay of about 7 seconds starts. If during this time you manage 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 a relay can connect or disconnect up to 12 loads.

After 7 seconds, the “Hang Up” relay will work (its contacts are connected to the “hang up” button), and for subsequent control you will need another call. Thus, it turns out that the phone will simply be completely wrapped in wires: wires from the relay to the buttons and even the DTMF signal output from the headset jack.

A simpler diagram, referring to the number of parts, is shown in Figure 7.

Figure 7. Diagram of the load control device by phone (click on the picture to enlarge)

This is where a phone is used with automatic hook-up when a headset is connected, so there is no need to solder to the buttons, you just need to connect the headset connector. This circuit provides control of 8 loads; control commands are shown in the circuit description.

But these schemes are not at all the ones that were called the most complex and serious at the beginning of the article. There are those who use a built-in GSM SIM300D module instead of an old cell phone. Its price is 4200 rubles, although it has already been discontinued. It is into this module that the SIM card is inserted.

Read more about how to independently assemble and program a remote control device in your own design here:

Step-by-step instructions on how to independently assemble and configure a load control device using a mobile phone -

We now have many cell phones in our hands, each of which can be turned into a GSM alarm system

their battery is either completely dead, or the case is broken, or the buttons don’t work well, and they’re simply outdated models, but reliable and completely functional.

The idea of ​​using a telephone as part of an alarm system is not new. Back in the days of wired telephones, there were schemes that allowed dialing to a pre-programmed number. With the advent of cellular communications and telephones that allow dialing without additional circuitry, it became possible to create simple and effective ones for use in everyday life and unlicensed projects.

The advantages are clear:

• mobility;
• Possibility of use at sites without mains power supply;
• it is easy to change the numbers to which calls are made;
• easy to change the operator (by changing the SIM card);
• when using a tariff without a subscription. fees and with free dialing to your operator’s numbers, operation is as cheap as possible.

But don’t forget about the nuances of cellular communications:

• cellular communication is not ideally efficient (professional work of the operator, communication is not provided in all points of space, and the phone is no no and glitches);
• attackers can easily block the operation of the phone by jamming or shielding the protected object.

However, GSM and GPRS alarms have better signal encoding and are less energy consuming than radio security systems, and there is no need to install an antenna on the site.

Okay, enough preludes, let's move on to “our sheep.”

The idea was born a long time ago when I learned to use the button quick dial. At first everything seemed simple - I assembled a simple delay circuit that would be controlled by the sensors of the security loop and full speed ahead, control the fast dialing. I scoured the Internet, didn’t find anything worthwhile except the same proposals from smart people like me, and began to move the topic forward.

I assembled a time relay from a field-effect transistor and a capacitor and stepped on the first rake: such a simple circuit is poorly controlled by sensors (there is a short response time and contact bounce).

The second rake appeared during the development process: any information on the phone screen could completely block dialing (moreover, different brands of phones behaved differently). And finally, when the cold weather set in, the third rake appeared: the phone (in the garage) began to fail.

Another rake appeared when searching for the keys with which to “press” the phone buttons (galvanic connection of the control circuit with the phone circuit is unacceptable, otherwise the buttons, although controlled, completely change their values).

And one more rake - for working in a buffer with (so that it would be economical and maintain the battery in a state of slight undercharging).

Taking into account the above, the concept of implementation emerged, moreover, any push-button telephone, including sliders and clamshells. Firstly, you need to control the phone using a circuit that generates time delays. Secondly, switches with galvanic isolation are needed (special microcircuits like 564KT3, optocouplers, or commonplace electromagnetic relays). Thirdly, the phone needs to be thermostatted. And fourthly, for all this disgrace you need a reliable and economical power supply.

A time delay generating circuit is needed so that when the sensor is triggered there is time to dial and listen to the object, this is approximately 30 seconds.

During these 30 seconds, three more delays occur:

1. The red “Reset” button turns on for half a second to reset any information on the screen;
2. pause for one or two seconds (without a pause the phone becomes glitchy);
3. and finally, a 4-second activation of the speed dial button.

To implement such an algorithm, I used four standby multivibrators. There are a lot of options for their implementation, but at my disposal was the well-proven K561LA7 microcircuit. Based on two microcircuits, I implemented four standby multivibrators. The telephone buttons were controlled using a 564KT3 microcircuit (optocouplers are excellent, telephone buttons are switched with a key resistance of up to 200 Ohms, the best result is with solid-state relays (for example AQY 212).

Since I oriented the alarm system for , I used sensors to short circuit. And I rolled back the circuit in the same way with short circuit sensors. Although it is more correct to make an alarm with sensors to open, then the circuit is more noise-resistant, and the security ones are usually open.

The main part of my research was carried out in the conditions of a stand, in winter. I checked how various phones work in cold conditions and found that all phones do not tolerate cold well. The assembled phone, even in a case and in a pocket, is functional in fairly cold weather outside. In my case, all the phones were disassembled, with the battery soldered with wires.

First of all, as a rule, even at zero temperature, the part of the phone circuit responsible for pressing buttons begins to malfunction; it may not turn on or dial something else. At low subzero temperatures, the radio module fails, the phone seems to work, but may not see an incoming call, or may not transmit. Cured by packing the carcass of the phone in polystyrene foam. Even with it removed, it remained operational at 27 degrees below zero (we didn’t go any lower).

I still haven't found the best option for the power supply. I'm inclined to think that it should be controlled by a controller. The fact is that I am initially developing a system with a primary source of 12 volts (for example, an old car battery). All converters and stabilizers DC-DC 12 to 5 volts have a certain efficiency, and linear stabilizers completely dissipate power in vain. (This does not apply to the case when you have a 220 volt network at your disposal and losses can be neglected.)

To better understand the problem, we need to remember the features of lithium batteries. It would seem that it would be easier to take and connect the phone with the battery inserted to the charger? You can - the security function will remain, after the charging is complete, the phone will write “charge complete” and will wait for the next discharge. But in my developments, to listen to an object when triggered, I use a response by pressing “any” button, carried out by the vibration alert voltage through an optocoupler.

When you connect the charger, the vibration alert mode on most phones is disabled. Yes, and phones often do not have original batteries, but there are batteries from broken ones, and they have to be soldered on the wires.

When trying to connect a five-volt power supply to a lithium cell in the buffer, in the hope that the battery protection circuit will turn it off when it reaches a charge, we step on a RAKE. Such a big rake, because after the protection circuit disconnects the battery, the phone continues to work from the power supply, and its current is not enough to maintain the operation of the radio module and the phone simply turns off when trying to go on air. Secondly, lithium batteries, being constantly under 100% charge, begin to slowly but surely die. It is optimal to keep them at 70 percent of full charge. This is quite easy to achieve; it is necessary that the power supply be adjusted to a voltage of 4.2 - 4.25 volts and there is no charging current.

In this case, the adjustment must be carried out in several stages, as the battery charges and the entire load, naturally, must be turned off, and the battery at the beginning of the charge should have no more than 50% charge.

As the battery charges, the voltage on the battery increases and the current decreases.

To limit the charge current (and in order to prevent the destructive consequences of a short circuit in the electrical circuit), I introduced two 28V 2.8W incandescent lamps in parallel into the 12V power circuit. In this case, the current even short-circuit. slightly exceeds 200mA.

Now a few words about which power supply to choose.

When the entire circuit operates in steady state, when the battery is charged to its nominal value, the current consumption from a 12 volt source is about 15mA, even turning the phone into dialing mode does not significantly and briefly increase the current.

These 15 mA break down approximately like this: 5mA – current consumed by the microcircuit; 5mA — average phone current; and another 5mA – the current consumed by the pulse converter (even in idle mode). By the way, in x.x mode. a linear stabilizer (for example, on LM217) consumes practically nothing, but at maximum current it heats up like a stove.

And now, my patient reader, let me remind you what I said at the beginning, and what I said was that my first experiments were with a time relay on a field field and this scheme was the most economical, which is what I tried to achieve (to give credit where credit is due, it worked I’ve had it for about half a year and without a single glitch (although I managed to turn it off under test conditions).

In the photo, checking the circuit for stand, SAMSUNG phone, later replaced by NOKIA in foam and six months in the garage for sea trials. This set is now disassembled. Although the idea of ​​assembling a time delay circuit using transistors exists.

But this option is not universal and requires dancing with a tambourine for each phone. And now I can replace the phone in any of my circuits without any problems - complete unification. A 42A/H battery, which did not turn the starter on the car, lasts for almost two months (it’s easy to calculate: 15mA*24hours*50days =18000ma/h, i.e. 18A/H, which is approximately the charge this battery takes).

Now I am putting together my projects in the direction of GSM signaling, based on the ATtiny13 pic-controller, this is a small, cheap chip with a supply voltage of 2.7 - 5 volts, which allows it to be powered from a phone battery. With minimal body kit, you don’t even need an external generator, however, the built-in generator does not allow you to reduce the clock frequency, which would further reduce power consumption. I use AQY212 solid-state relays as keys (you can use any, I bought 100 pcs from AliExpress for 900 rubles with delivery). I didn’t come to the optimal solution with power supplies. I installed an alarm on the car with a power supply on two KRENs, one is a current stabilizer, the second is a voltage stabilizer. In the latest designs I use pulse converters. In order not to collect, I pay 150 rubles. I buy a USB charger from the cigarette lighter, remove the board from it, remove the connector and unnecessary radio components from the board, solder a 5kOhm multi-turn potentiometer to adjust the output voltage, and before the converter I solder two 28V 2.8W lamps in parallel.

I put all this disgrace in a foam box, temperature control is carried out by the power supply. At currents up to 200mA, overheating does not occur.

In one of the first units, the charging current of a discharged battery rose to 300 mA, there the heating was good, after which we had to take a closer look at the power supplies.

This device is now guarding my and my neighbor’s garage (two loops with dialing to two numbers).

These were theoretical calculations with practical examples, and now there is little that a radio amateur who can more or less know how to hold a soldering iron and distinguish a resistor from a capacitor can repeat, otherwise there was no point in reading all of the above.

This is a diagram for wiring a shortcut button with a time delay based on a mosfet. The circuit is quite working, assembled

and checked.

I take mosfets from boards of dead computers. They look like the photo below, a microcircuit with eight legs, of which four are soldered into a pile, three into a pile and one separately.

Why they are good: they are controlled by a low potential, therefore the control circuit is economical, they work very stably and in a wide range of ratings of the radio elements used, the power decoupling from the phone buttons is ensured by a high resistance in the control electrode circuit.

This scheme will work if, when the phone screen is turned on, the number is not redialed, otherwise it is necessary to block the dialing, powering it from the screen backlight. (MOTOROLLA 114 did not require blocking, NOKIA requires blocking. This is done by short-circuiting to minus the point between the 6.2 kOhm resistor and the sensor, the same mosfet powered from the screen backlight)

In this scheme, it is necessary to use “short circuit” sensors.

There may be a short time when the sensor is in the triggered state; as a result, quick dialing will not occur and the number will freeze on the screen; further quick dialing will be possible after resetting with the “C” button. Nokia does not reset by dialing! In this case, the SMS center must be turned off so that SMS messages do not arrive on the phone.

Now you understand why I went towards schemes that work according to a given program!

Here is a scheme that works according to a given algorithm:

The circuit is assembled on two K561LA7 microcircuits. Ex. “C” - pressing the “reset” button, ex. “B” - pressing the quick dial button must be done using optocouplers, or, like mine, with a 564KT3 microcircuit. The circuit can be powered directly from a 12-volt battery, or a 6-15 volt power supply.

The most flexible, in terms of operating algorithm, circuit assembled on a pic controller. There are a lot of implementation options, depending on what we want to get in the end. The number of radio elements is minimal, which allows you to make a small board. Power supply from 2.7 volts to 5 volts, respectively, we power it from the phone battery (you don’t even need to use a 12 volt battery if the capacity of the lithium cell is sufficient for long-term operation).

But not all radio amateurs may be able to implement the circuit on a controller. You need to flash the chip, you need a programmer, you need firmware. At the moment, I have four firmware written, three are loaded into the microcircuits and are working.

Here is a variant of one of the basic diagrams:

... I put an ellipsis because I consider the article unfinished, experiments continue. Recently, the circuits on the controller have occasionally generated false alarms, presumably due to high sensitivity along the loop circuit. It is necessary to either add a key element at the input of the microcircuit, or correct the firmware.
I’ll also try, in my spare time, to assemble a circuit using mosfets that works according to a given algorithm. I feel this will be the most economical and noise-proof circuit.

See also:

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One of the elements of a “smart home” is a “smart socket”. It is much easier to buy a GSM socket, but it is quite possible to make it yourself. It supports the GSM digital mobile communication standard and can be used to turn on and off alarm systems in a house or apartment. Since such devices are currently widely represented on the market (there have been quite a lot of cheap Chinese handicrafts recently), purchasing it at an adequate price is not a problem. But some people prefer to make such sockets themselves.

Brief description

A “smart socket” can be used to implement the following functions:

1. Remote control of household appliances: kettle, stove, boiler, etc.
2. In business premises, you can remotely connect computer equipment.
3. The GSM socket allows you to turn on and off the automatic watering system in your garden plots.
4. When connecting air conditioners and heating devices to such a device, it is possible to adjust the microclimate of the room.
5. This socket is well suited for security alarm systems.
6. If necessary, you can urgently turn off the power supply to the room.

It is important to note the disadvantages that the SMS socket has. These include:

• the need for a power supply that will smooth out voltage drops in the network (they can damage the GSM switch),
• Quite a lot of power consumption for one device (the communication module draws a lot of power),
• complexity of production and high cost of components.

In this case, a remote-controlled socket can be automatically turned on or off from fairly large distances using mobile communications (for example, a call or SMS message).

The GSM socket itself with a temperature sensor looks like a regular adapter that plugs into a regular socket. Household appliances connected to it turn on after a call or SMS notification; in addition, a smart socket almost always has manual control (as a backup). However, such sockets are designed for a load of up to 5 kW, which limits their use. The cost of factory products currently reaches 3 thousand rubles (minimum cost 900 rubles), while the cost of components for self-production is about 2-2.5 thousand.

A little physics: description of the process

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Currently, modern telephones use tone dialing. Such signals are called DTMF signals. Their sound depends on the combination of frequencies, and the frequencies are selected in such a way that harmonics are not formed. Therefore, to decipher the frequency, you need to install a decoder (you need to purchase it to make the switch yourself). Accordingly, if, after connecting, you start pressing the number buttons on the phone, the person being called will hear their tones.

A similar socket is created based on the principle of tone decoding. Pressing keys controls turning on and off such devices.

The simplest design

Here are instructions on how to make a tone decoding device that can control a primitive relay. It is the relay that will turn the contacts on and off, and the signals to it will come from the decoder.

A primitive controlled socket requires, at a minimum, the purchase of a polarized relay.

Now let's move on to the description of the scheme. The main device is the mentioned polarized relay. It has 2 coils connected in such a way that when one of them is connected to the network, the armature is attracted to one of the relay cores and does not open the contact even after the power supply is stopped. In order for the contact to move back to its original position, an impulse (voltage supply) is required to the second coil. In this case, the pulse must be of a given amplitude and duration.

To power such a device from the network, it is necessary to solder a diode rectifier. Usually it contains a capacitor designed for a voltage of 24 V. Such a circuit seriously violates safety regulations, but its careful use for loads of no more than 3 kW will not lead to serious accidents.

As a receiving module, you should have either an old mobile phone or a special receiver with a decoder. It’s easier to buy a primitive mobile phone with a vibration alert function. An optocoupler relay is connected to the vibration alert; when connecting, you should check the polarity of the voltage at the vibration alert outputs; this is important, since the relay has “+” and “-” output contacts. Vibration alert significantly simplifies the operation of the circuit.

When the vibration mode is triggered, a transistor opens in the optocoupler relay, which charges the capacitor from the socket through one of the relay windings, and an open transistor (all this happens in the relay circuit). Next, the armature switches and turns on one of the coils of the polarized relay, which closes one of the contacts (to turn on the mains voltage or turn it off).

The polarizing relay is a starter. Next, after the capacitor is discharged (when the vibration stops), the capacitor is discharged, which moves the armature of the optocoupler relay to its original position. When vibration is repeated and the optocoupler relay is activated again, the armature of the polarized relay will switch to another coil and the circuit will be disconnected. In this case, there is no need to set up your mobile phone again, just calling the number is enough.

The disadvantage of this scheme is that the relay will be triggered when SMS spam is sent.

Hello friends! I want to tell you how you can create something useful using an old mobile phone. Namely, this will be the simplest GSM alarm system, with which you can remotely control various objects, such as a cottage or apartment.

What do we need

• any mobile phone with a push-button keyboard;
• soldering iron;
• two screws;
• unused bank plastic card;
• clothespin;
• two neodymium magnets in the form of tablets with a diameter of about 10 mm;
• a rectangular plate made of plastic or plywood measuring approximately 50x100 mm.

Let's get started

Conclusion

I needed to remotely start a heating boiler, but otherwise you can start whatever your heart desires. What signal do we have everywhere and everywhere...? That's right, GSM. So, the cheapest GSM receiver is..? That's right, old sotik. Any beginning radio amateur can assemble the device. What were the priorities when developing this device? Simplicity, low cost, minimum radio components.

Total we need

1) Cell phone, with vibration

7) Hands (It doesn’t matter where the hands come from, as long as they are golden!)

And so let's get started

We disassemble the cell phone, go where the motor is located and solder to its contacts

I had an old smart device on hand, I removed the motor altogether, by the way, it is advisable to remember where the plus and minus are when connecting to an optocoupler, this matters.

You need to set up your phone so that vibration is triggered for an incoming call, but the vibration alert does not trigger for SMS, notifications, mail, MMS and any other junk, in order to eliminate false positives, you need to set up a call filter (optional on each phone), you can order it from the operator, but this service comes with a subscription fee. Let's put together a diagram.

Everything works like this, we call, the phone receives a signal and sends voltage to (which is no longer there) the voltage goes to contacts 1 and 2. The optocoupler opens and passes the current of relay K1 through itself, the relay is triggered and self-powered through contacts K1.1, through the same contacts, a minus appears on the OUT pin. The circuit will remain in this state until the power is removed from it. How you choose to remove food is your choice. D1 is necessary to prevent the load current from passing through the optocoupler when the relay is turned on (the optocoupler has a current limit, and a load current of, say, 2A will quickly damage the device).

Since there are few parts, I assembled everything using a hinged installation, directly on