It is proposed to carry out local wireless telephone communication at the dacha, to provide retransmission of music and news programs at any point of the site. And all this is practically free, using the slogan – “New life for old things”.
Mobile phones have taken a stable place in our lives and have practically replaced other means of communication. However, it became sad when I once again came across a box with an abandoned DECT phone. Convenient and perfectly working in the recent past, but today outdated wireless phone PANASONIC KX-TG8105RU. It was a pity for the high-quality, but uselessly lying thing, its unspent working potential.
But a new summer cottage season is coming, and with it the attendant problems – unstable mobile communications in this area and another rise in the cost of using it. This situation prompts the search for a way out. And a partial solution will be the installation of telephones in the dacha using the specified wireless telephone. This will allow you to talk to your closest neighbors for free, hear news and music anywhere in the country. It will be possible to use the network as an intercom or use it in the security system.
Organization of a telephone network at the dacha
Organizing a minimum telephone connection at the dacha will not be difficult. It is enough to connect in series another base with handsets or an ordinary wired telephone set (such as TA68 or TA72) to the DECT phone base and close the circuit by connecting a battery in series with a voltage of 5 to 12 V.
The number of network subscribers can be increased by adding additional wired or wireless telephones to the chain.
Network functions can be supplemented by the ability to transmit to the handset the radio signal picked up from the telephone jack of the radio or TV. For this, the winding of the output transformer from the portable receiver is additionally and in series connected to the telephone network, the other winding is connected through the plug to the signal source.
For comfortable and loud listening to broadcast programs, the DECT handset is switched to the “Speakerphone” mode.
As a result, the minimal scheme of a country telephone network will be as follows
There are also disadvantages.
For voice transmission in telephone communications, the frequency range 300Hz… 3.4 KHz is used, which will limit high frequencies.
Another negative point will be the consumption of batteries that are not cheap today.
For this reason, it is advisable to immediately abandon the use of batteries and replace them with batteries.
Making a power supply unit for a telephone network
The best option would be to install two lithium – ion batteries (2 x 3.7 V) connected in series. You can install other batteries available (as in the example below), the main thing is to set the required battery voltage in the range of 5 … 12 V.
Having installed the battery, you will need to monitor the state of its charge and periodically remove it for recharging. Therefore, it is easier and more practical to install a battery in the power supply unit being manufactured, make a charger for it and install there a charger with a charge indication.
For high-quality battery charging and its long-term operation, we will manufacture a charger with adjustable limitation on the maximum voltage on the battery, with regulation and stabilization of the charging current.
The range of application of such a charger is wide. Consider one of the options for its use in this example in a battery power supply.
The charger circuit with the given characteristics is as simple as possible and consists of the available components.
Low-power control transistor VT1 performs the function of stabilization and regulation of the charging current, controls the transistor VT2.
Power transistor VT2 regulates the main current of the battery charge.
On the Zener diode VD1 there is a regulator of the output voltage of the charger.
The LED1 LED informs about the operation of the voltage regulator and serves as a visual indication of the battery charging process.
Diode VD2 protects the battery from discharge.
Input contacts X1 for connecting the charger to a 12V power source.
Contacts X2 for connecting the battery to the telephone network and/or other load (for example, an LED desk lamp).
Making a charger
1. Power supply enclosure
Traditionally, at the first stage, we select a case for the manufactured device. It will determine the dimensions of the electronic board, the location of switches and connectors, the appearance and layout of the device.
Since I have at my disposal unused elements from the NiMH battery of the screwdriver and the case from it, in this device we will take them as a basis.
Let's assemble five elements into a block, connect them in series by soldering the remaining jumpers. As a result, we get a battery of accumulators with a nominal voltage (1.2 V x 5) 6.0 volts. A full battery charge will be possible up to (1.8 x 5) 9.0 volts.
We will install a power switch and connectors X2 in the case.
2. Building and debugging the schema
According to the given diagram, we find or purchase component parts. We assemble the charger on the universal circuit board. We connect the circuit to a 12V DC power source. It can be a purchased power supply unit or a 220/12 V transformer with a bridge rectifier.
Selecting the values of the resistors R4 and R5, we achieve adjustment of the output voltage at the X2 terminals (no load) in the range of 3 … 10 V.
Let's connect the battery pack as a load to the charger, check the possibility and range of charging current adjustment. With R3 rated according to the scheme (1.8 Ohm), on a block of five available batteries, the current is regulated from 0.1 to 0.6 A at a set output voltage of 9 volts. On one element, the current is regulated to 1.6A.
3. Mounting the circuit on the working board
In accordance with the internal dimensions of the device case, we cut out the working board from a typical universal board. In its upper part we will install variable resistors R2 and R4 to adjust voltage and current.
To reduce the temperature effect on other parts, improve the operating mode of the power transistor VT2 (installed on the radiator) and the limiting resistor R3, which have a large heat release, it is advisable to separate these parts from the rest of the circuit and ensure their natural ventilation. In the used case, such a possibility is available. We will install these parts separately, on short conductors, and in the future, we will place them in the upper part of the case. We will execute the rest of the circuit on the working board. Putting together the entire circuit and checking the charger.
4. Manufacturing a block of telephone network connections
For compactness and mobility of the device, we will combine the battery pack, charger, relay transformer and connection unit in one case.
When mounting the charger, on the working board, we leave free space for the installation of the transformer for transmitting the signal from the source to the telephone network. We use an output transformer from an old portable radio. The output winding is included in the break in the telephone network, the primary winding is connected to the Jack or Tulip audio connector with its installation on the body.
< a href = "https://usamodelkina.ru/uploads/posts/2021-04/1617384390_11.jpg" rel = "prettyPhoto"> The block of connections of installed telephones to the telephone network is easiest to organize using a standard telephone cable and a telephone block.
We disassemble the block, disconnect and remove the contact pins, connect the two middle contacts of both telephone connectors in series.
Place the Tulip (or Jack) connector on the free space in the block.
Fix the block on the case in a convenient place.
We bring the necessary conductors inside the case.
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5. Final assembly of the battery power supply
We assemble all units of the device into a single structure.
The hot parts of the charger are installed and fixed in the perforated case cover and connected to the working board with short conductors.
The charge indicator (LED LED1) is installed in the upper part of the case.
Let's complete the complete wiring diagram. To the input contacts X1 of the charger we will connect a cable with lugs to connect to the current source.
Install and fix the charger board in the case. If necessary, to exclude unwanted contacts, install protective textolite pads between the board and other open contacts.
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It remains to collect and check the operation of the local telephone network.
We connect the manufactured power supply to a 12 V current source and charge the batteries. When the batteries are discharged, the indicator does not light up; as the charge progresses, the indicator becomes brighter.
The cordless telephone base is connected with a telephone cable to the connection node installed on the power supply unit. We connect the base of the phone to the 220 V network. With another cable, we will connect the second (for example, wired) phone in the same way. We pick up the phone and go, for example, to the gazebo. The telephone network is ready for conversation.
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When you connect a radio receiver to the Tulip connector, anywhere in the country you can hear news from the tube within a couple of meters or “favorite” advertising, just press the “Speakerphone” button on the handset.
There will be no problems with charging the handset batteries, they are automatically recharged when idle, when the handset is placed on the base.