Make your own radio that works without batteries. A simple radio receiver circuit: description. Old radios

You will need just one chip to build a simple and complete FM receiver that is capable of receiving radio stations in the range of 75-120 MHz. The FM receiver contains a minimum of parts, and its configuration, after assembly, is reduced to a minimum. It also has good sensitivity for receiving VHF FM radio stations.
All this thanks to the Philips TDA7000 microcircuit, which can be bought without problems on our favorite Ali Express.

Receiver circuit

FM Receiver Board

Placing elements on the board

Receiver setup

Conclusion

Radio stations operate in the medium wave range, their signals literally surround us. To assemble a radio receiver with amplitude modulation(AM receiver), you will need several simple details: some electronic components, wires, paper tube and speaker. Assembling the AM receiver is quite simple and does not require any soldering. With this simple receiver you will be able to pick up signals from radio stations that are within 50 kilometers.

Steps

Part 1

Prepare what you will need. You may already have most of the parts you need, with a few exceptions. electronic components. Missing parts can be purchased at a hardware or electronics store. You will need the following:

• resistor with a resistance of 1 megaohm;
• capacitor with a capacity of 10 nanofarads;
• red and black insulated wires 25–50 centimeters long;
• variable capacitor with a capacity of 2000 or 2200 picofarads;
• electrolytic capacitor with a capacity of 22 microfarads;
• capacitor with a capacity of 33 picofarads;
• insulated wire 15–30 meters long (any color, for the antenna);
• 9-volt battery;
• breadboard;
• insulating tape;
• operational amplifier(OU);
• a small non-conductive cylinder (glass bottle, cardboard or plastic tube, etc.);
• speaker;
• wire cutters (or something similar, such as sharp scissors or a knife).

1. Make an antenna. This is one of the simplest parts of a homemade radio: all you need is a long piece of wire. It's best to use a 15 meter piece of wire, but if you don't have that long of wire, 5-6 meter long wire will do.

   • For the antenna, insulated wire with a diameter of 0.7–0.8 millimeters is best suited.
   • To make the antenna better receive the signal, roll the insulated wire into a ring. To prevent the wire from tangling, secure it with a cable tie or electrical tape. Fold a 15 meter long piece of wire about five times into a ring.

2. Cut and strip the connecting wires. These wires will be used to connect the components on the breadboard. electronic circuit. Cut one piece of red and one black wire about 12 centimeters long.

   • Using wire cutters, strip 2-3 centimeters off both ends of each wire.
   • If the connecting wires turn out to be too long, they can always be cut, so it is better to make them with a small margin first.

3. Make an induction coil. Wrap the wire tightly around the cylinder without gaps between adjacent turns so that it receives radio waves carrying electromagnetic energy. It's not as difficult as it seems at first glance. Simply thread red and black wires 25–50 centimeters long onto the cylinder.

   • Start winding the wire from one end of the cylinder. Leave about 12 centimeters of wire free at the end to secure it with insulating tape to the edge of the cylinder. Wind the wire tightly without any gaps between adjacent turns.
   • Select a cylinder with a diameter of 5–8 centimeters. It should not be metal, otherwise the received signal will go through the metal.

4. Completely wrap the cylinder with wire to create an induction coil. The more turns you get, the better. Cover the entire cylinder with wire. Secure the end of the wire with insulating tape, measure about 13 centimeters at the other end and trim off the excess wire.

   Connect a 22 microfarad (µF) electrolytic capacitor. Place the long lead of the 22uF capacitor on the top half of the breadboard in the hole directly above top contact resistor 1.0 M. Insert the short lead of the capacitor into the hole four rows to the right.

   Install the connecting wires. Insert one end of the red wire into the hole above leg 8 of the op-amp, and the other into the nearest hole in the top long row of the breadboard, where the holes are connected horizontally. Insert one end of the black wire into the hole under amp leg 1 on the bottom half of the breadboard. Insert the other end of the black wire into the bottom long row of the layout.

   Install a 33 picofarad (pF) capacitor. Take a look at the 10 nF capacitor. One of its terminals is connected to the bottom leg of the amplifier, and the second is inserted into a free hole, but is not yet connected to anything. Insert one lead of the 33 pF capacitor into the hole above the free lead of the 10 nF capacitor. Insert the second lead of the 33 pF capacitor into the free hole four rows to the left.

   • This capacitor, like the previously installed 10 nF capacitor, has no polarity and allows current to pass in both directions. So it doesn't matter which pin is used where.

Part 3

1. Connect the antenna. It's time to connect the antenna. Insert one end of the antenna into the hole above the free lead of the 33 pF capacitor (you moved this lead four rows to the left in the previous step).

   • To improve signal reception, you can spread the antenna wire around the room or twist it into a ring, as described above in the antenna preparation step.

2. Connect the variable capacitor. Insert one lead of the variable capacitor into the hole above the right terminal of the 33 pF capacitor. Place the second lead in any hole in the very bottom row of the layout, where it will connect to the black wire.

   Connect the inductor. Use the free ends of the wire about 12 centimeters long that are left on both sides of the coil. Insert one end into the hole in the bottom row of the breadboard where it will connect to the variable capacitor and black wire. Insert the second end of the wire from the coil into the hole in the row where the 10 nF capacitor and the electrolytic capacitor are connected.

   Connect the speaker. Place the speaker on the table to the right of the variable capacitor. The speaker has two terminals, black and red. Unravel them and get them ready to join. Insert the red speaker lead into any hole in the top row breadboard where it will connect to the red wire. Place the black speaker wire in the hole above the short lead of the 22 µF electrolytic capacitor.

   • You will probably have to unwind the red and black speaker wires so they can be connected to the circuit.

3. Connect the power supply. After you assemble the circuit, you need to provide it with power. Using electrical tape, connect the wires to the positive and negative terminals of the 9-volt battery. Then do the following:

   Listen to the speaker. After you connect the circuit to the power source, the amplifier and speaker will flow electric current. The speaker should begin to make sounds, although this may be simple noise and interference caused by static electricity. This indicates that all components are connected correctly.

4. Check if all components are working properly. If you have assembled the circuit correctly and made sure that all contacts are reliable, it is possible that the problem is a malfunction of some components. Capacitors, resistors and op-amps are very cheap and produced in large quantities, so sometimes there are faulty components among them.
5. Buy a voltmeter that you can use to test the circuit. A voltmeter allows you to measure the current that flows through the section of the circuit you are interested in. Voltmeters are pretty cheap. With this device you can check the components of the circuit and the reliability of their connections.

Warnings

• Don't overload the circuit high voltage. If you apply more than 9 volts, the components may fail and even catch fire.
• Do not touch bare wires while current is flowing through the circuit. Otherwise, you may get an electric shock. However, since this circuit uses a low voltage battery, the shock will not be severe.
• Do not connect the short lead of the capacitor to the positive terminal of the voltage source. If you do this, there will be a popping noise, the capacitor will release a small cloud of smoke and fail. In the worst case, it may catch fire.

What you will need

• 1 resistor with a resistance of 1 megaohm
• 1 10 nanofarad capacitor
• Red and black insulated wires 25–50 centimeters long
• Variable capacitor with a capacity of 2000 or 2200 picofarads
• 1 electrolytic capacitor with a capacity of 22 microfarads
• 1 capacitor with a capacity of 33 picofarads
• Insulated wire 15–30 meters long (any color, for antenna)
• One 9-volt battery
• Development board
• Insulation tape
• 1 operational amplifier (op-amp)
• A small cylinder of non-conductive material (glass bottle, cardboard or plastic tube, etc.)
• Speaker
• Wire cutters (or something similar, such as sharp scissors or a knife)

Radio

A previously home-made simple loud-speaking radio receiver with a low-voltage power supply of 0.6-1.5 Volts is idle. The Mayak radio station on the CB band went silent and the receiver, due to its low sensitivity, did not receive any radio stations during the day. During the modernization of a Chinese radio, the TA7642 chip was discovered. This transistor-like chip houses the UHF, detector, and AGC system. By installing a ULF radio in a single transistor circuit, you get a highly sensitive loud-speaking direct amplification radio receiver powered by a 1.1-1.5 Volt battery.

How to make a simple radio with your own hands

The radio circuit is specially simplified for repetition by novice radio designers and is configured for long work without turning off in energy saving mode. Let's consider the operation of a simple direct amplification radio receiver circuit. See photo.

The radio signal induced on the magnetic antenna is supplied to input 2 of the TA7642 chip, where it is amplified, detected and subjected to automatic adjustment gain. Nutrition and eating low frequency signal carried out from pin 3 of the microcircuit. A 100 kOhm resistor between the input and output sets the operating mode of the microcircuit. The microcircuit is critical to the incoming voltage. The gain of the UHF microcircuit, the selectivity of radio reception over the range and the efficiency of the AGC depend on the supply voltage. The TA7642 is powered through a 470-510 Ohm resistor and a variable resistor with a nominal value of 5-10 kOhm. Using a variable resistor, you select best mode the receiver's performance according to the quality of reception, and the volume is also adjusted. The low frequency signal from the TA7642 is supplied through a 0.1 µF capacitor to the base npn transistor and intensifies. A resistor and capacitor in the emitter circuit and a 100 kOhm resistor between the base and collector set the operating mode of the transistor. Load specifically in this option The output transformer from a tube TV or radio is selected. The high-resistance primary winding, while maintaining acceptable efficiency, sharply reduces the current consumption of the receiver, which will not exceed 2 mA at maximum volume. If there are no requirements for efficiency, you can include a loudspeaker with a resistance of ~30 Ohms, telephones or a loudspeaker into the load through a matching transformer from a transistor receiver. The loudspeaker in the receiver is installed separately. The rule will work here: the larger the loudspeaker, the louder the sound; for this model, a speaker from a widescreen cinema was used :). The receiver is powered by one AA battery 1.5 Volts. Since the country radio receiver will be operated away from powerful radio stations, it is possible to turn on external antenna and grounding. The signal from the antenna is supplied through an additional coil wound on a magnetic antenna.

Details on the board

Five splat pins

Chassis board

Back wall

The housing, all elements of the oscillatory circuit and the volume control are taken from a previously built radio receiver. See details, dimensions and scale template. Due to the simplicity of the scheme PCB was not developed. Radio parts can be installed by hand using a surface-mounted installation or soldered on a small area of ​​a breadboard.

Tests have shown that a receiver at a distance of 200 km from the nearest radio station with a connected external antenna receives 2-3 stations during the day, and up to 10 or more radio stations in the evening. Watch the video. The content of evening radio broadcasts costs the production of such a receiver.

The contour coil is wound on a ferrite rod with a diameter of 8 mm and contains 85 turns, the antenna coil contains 5-8 turns.

As stated above, the receiver can easily be replicated by a novice radio designer.

Do not rush to immediately buy the TA7642 microcircuit or its analogues K484, ZN414. The author found the microcircuit in radio receiver costing 53 rubles))). I admit that such a microcircuit can be found in some broken radio or player with the AM band.

In addition to its direct purpose, the receiver works around the clock as a simulator of the presence of people in the house.

To receive a local radio station, you can assemble a simple detector receiver. And when using a small radio component - transistor you can amplify the signal tens or hundreds of times. The transistor consumes very little energy and is capable of operating even at a voltage of about 1 V!

Radio receiver circuit

The circuit of the receiver described below contains only one transistor (see figure). The thing is that the headphones are in the collector circuit. In this mode, the transistor provides greater signal amplification.

Two inductors are placed on a common ferrite rod - loop inductor L1 (with variable capacitor C1 it makes up the already known oscillatory circuit) and communication coil L2. The number of turns of the coupling coil is significantly less than that of the loop coil, and only part of the received signal is received by the transistor. This is done so that the transistor does not affect the oscillatory circuit and thereby does not change its settings.

So, from the coupling coil the signal goes to the base of the transistor through capacitor C2. Here it is detected, that is, a signal is extracted from it audio frequency, which is then amplified by a transistor and sent to headphones.

Bias is applied to the base of the transistor through resistor R1. In the diagram, you see an “asterisk” next to the letter designation of the resistor. It shows that this resistor may have to be selected (that is, its resistance must be specified) when setting up the receiver. This will be discussed later.

Receiver installation

The coils are wound on a ferrite rod with a diameter of 8 mm and a length of 40 - 50 mm. Coil L1 contains 80 turns, and L2 - 20 turns of PEL or PEV wire with a diameter of 0.15 - 0.2 mm. The distance between the windings is about 5 mm, the winding is turn to turn.

Mount some of the receiver parts on a board (see figure) made of insulating material, which resembles a detector receiver board. After installation, check the correctness of all connections and only then connect the power supply, headphones, antenna and grounding to the board racks (see figure). Using the switch, apply power to the receiver (a click should be heard in the headphones) and immediately measure the voltage between the emitter and the collector of the transistor - connect the positive probe of the voltmeter to the emitter circuit, and the negative probe to the collector circuit.

Receiver setup

The voltmeter needle should show a voltage of about 4.5 V. If it differs significantly (by more than 20%) from the indicated one, select resistor R1 - install another one instead (with lower or higher resistance).

It is not difficult to find out which resistor is needed. If the measured voltage is lower, you need to install a resistor with a higher resistance than that indicated in the diagram (for example, 390 kOhm, 430 kOhm, 470 kOhm, etc.). On the contrary, if the measured voltage exceeds the specified value, the resistor resistance should be reduced (install a resistor with a resistance of 300 kOhm, 270 kOhm, 240 kOhm). You can do it differently (see figure) - instead of resistor R1, switch on two series-connected resistors: constant resistance about 100 kOhm and variable (any type, for example SP-1, SPO-0.5) with a resistance of -4 MOhm. By moving the variable resistor slider, achieve the desired voltage, measure the resulting total resistance (the circuit must be unsoldered from the board) and install a constant resistor with approximately the same resistance on the board. In practice, such an adjustment rarely has to be done, since the required current transfer coefficient of the transistor is specified (60 - 100), and when using a transistor with this parameter, the bias resistor indicated in the diagram provides desired mode his work. All of the above is true, of course, only when using a fresh battery. Therefore, measure its voltage with the receiver connected (in other words, under load) - it should not be lower than 8.5 V, otherwise the battery will have to be replaced.

After checking and setting the voltage on the collector, touch the transistor base terminal with tweezers (or just your finger). There should be a faint hum in the phones - background AC. If the base is not touched, a faint noise should be heard in the phones, indicating normal operation transistor.

Now you can check how many radio stations and at what volume the homemade product you installed is receiving. If you notice that the sound in the phones is distorted, unwind one or two turns from the L2 communication coil. If the sound volume is excessive, connect between the outdoor antenna and the receiver's antenna jack permanent capacitor small capacitance (10 - 15 pF). In any case, you can change the operating range of the receiver using the same means as for the previous design.

Mount the board and parts that do not fit on it (sockets, connector, switch and battery) in a housing, which can be structurally the same as for the detector receiver. The power conductors can be soldered directly to the battery terminals or used to connect the battery to the receiver using a connector block from a worn-out Krona.

B.S. Ivanov, Electronic homemade products.

P O P U L A R N O E:

Anyone who has an old broken TV sitting idle, this article may be useful. TVs are usually installed full range speakers from 3 to 10 W. Today we will make small ones from them speaker systems— satellites. Satellite (eng. satelitte) is a column not large sizes(up to 20 cm in height), playing mid and high frequencies.

We offer all beginning radio amateurs to build detector radio. In Fig. 1 shown circuit diagram such a simple radio receiver.

Of course, you have already learned how to read device diagrams well and you can see for yourself that our radio receiver is of a very simple design, but at the same time it contains all the elements necessary to receive radio transmissions.
To “select” a wave desired radio station serves as a resonant circuit consisting of a coil L and a capacitor C. The signal, isolated from the sum of the signals of various radio stations, enters a diode detector, which converts the high-frequency signal into a low-frequency (sound) signal, and from it to the headphones.
To build a radio receiver you will need the following parts:
L - Inductor (as described below),
C - ceramic capacitor 220 pf,
A - receiving antenna (according to the description),
Z - grounding (according to the description),
D - diode detector (of any type, for example: D1A, D2B, or similar),
T - headphones (any type, maybe a small-sized headphone).
As you can see, our radio receiver does not have any amplifiers (tubes or transistors), nor does it have a power source. That's why headphones come in weak signals. That is why our radio receiver must have a good external antenna, at least 15-20 m long, and grounding. For grounding, they usually use a piece of copper wire connected to a water pipe.
The construction of a radio receiver should begin with the manufacture of a coil L. To do this, wind 100 turns of enameled wire with a diameter of 0.2-0.3 mm onto a tubular frame (made of any insulating material) with a diameter of 12-15 mm. Every 10 turns, make a winding output in the form of a small loop.

The coil manufacturing method is shown in Fig. 2.

Then insert a piece of ferrite rod (often called a ferrite antenna) with a diameter of 8-10 mm and a length of 10-15 cm into the tube. Do not secure it yet, this operation must be performed after setting up the receiver.

In Fig. 3 shown appearance assembled radio receiver.

When assembling, it is especially important to properly select the appropriate coil terminals for connection outdoor antenna and a diode detector. Select conclusions empirically, guided by the following instructions:
1. First, select a terminal for connecting an outdoor antenna by temporarily attaching a diode to one of the middle terminals of the coil. Your task is to find a conclusion at which the maximum audibility of the transmission in the headphones is at one of the middle positions of the ferrite rod inside the coil. If maximum volume happens when the rod is fully extended from the coil, you should use ceramic capacitor with a smaller capacity (for example, 100 pF instead of 220 pF) or not install it at all. And vice versa - if maximum audibility is achieved with the ferrite rod completely pushed inside the coil, you need to install a capacitor with a larger capacity (for example, 330 pF or more).
2. After setting up the resonant circuit, fix the ferrite rod inside the coil and find a terminal for connecting headphones (via a diode) at which the maximum transmission volume is achieved.
After selecting the appropriate leads, make a good mechanical connection of the receiver elements using an electric soldering iron and solder.
The operation of our receiver does not depend at all on the arrangement of elements on the circuit board, so mechanical assembly can be done in different ways. It is best to place the assembled elements in a plastic box of suitable sizes.
If the radio station you tuned to is located close to your home, and with a good antenna and grounding, you will get loud-speaking reception in your headphones. In this case, instead of headphones, we recommend connecting a loudspeaker with a transformer. The loudspeaker (with a permanent magnet) can be of any type, and must be quite large in size. As for the transformer, it is suitable for any radio receiver.
Do not connect small-sized loudspeakers and miniature transformers (from transistor radios), as the audibility of transmissions will significantly deteriorate. After replacing the headphones with a transformer-loudspeaker system, you should change the diode connection to the coil terminal. The transformer for powering the loudspeaker has two windings: thick and thin wire. Connect the winding leads from the thick wire to the loudspeaker, and the winding leads from the thin wire to the receiving system (Fig. 4).

Length best welcome For radio broadcasts, install the loudspeaker on a fairly large screen (partition) made of thick plywood.
Please note that a detector radio with a loudspeaker does not produce the same sound of broadcasts as a regular household receiver.
We wish you success in creating your first radio design.

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