I present to your attention a doorbell circuit that was assembled many years ago and has been in use for the same amount of time. It would be more correct to call this device: “Waste into income!” Because what it was made from was literally lying underfoot. This was during Soviet times. I was working at a small PBX at the time and had a lot of free time that I wanted to convert into money... Then I began collecting electronic calls based on this scheme and inserting them into . The installer of the city automatic telephone exchange willingly helped me with the implementation, making his own profit from it. The device imitates the sound of a bouncing ball. All characteristics are regulated by selecting the capacitor capacity and adjusting variable resistor.

Electrical circuit diagram

Once assembled without errors, it starts working immediately. Power supply is possible from a 12 volt DC source (then diodes D1-D4 and capacitor C4 are excluded). PBX ringing impulses alternating current 110 volts 25 hertz - in this case, the capacitance of capacitor C4 should be 1 microfarad per 400 volts.

AC voltage 220 volts 50 hertz, when used as an apartment bell (in this case, the capacitance of capacitor C4 should be 0.5 microfarads at 400 volts). The device was assembled using pieces of foil getinax, which were cut on a machine (Skillful hands) with a small circular cutter. I used one board as a conductor for drilling holes, but it can also be assembled using wall mounting.

Parts used

Transistor T1 - mp25-26, T2 - kt605 or p307-309, but p605 works better, diodes D1-D4 - D226, but others are possible, although D226 gave better results. Capacitors C1-0.1 C2-0.05, trimming resistor - 47k, C3 - 100 microfarads at 100 volts. The telephone capsule was used as an emitter, but only very old ones (large diameter).

The use of a Czech capsule with a resistance of 50 ohms gave very good results, but it has one feature - to achieve good volume, you need to remove the plastic plug from the side of the contact screws, under which there is an adjustment screw and, having turned on the device, use a small screwdriver to make adjustments, unscrewing and tightening screw to achieve maximum sound volume.

Warning! If you are going to use this device as a doorbell, do not set it up by connecting it to a 220 volt network! You might get hit high voltage! Set it up by connecting 12 volts to DC, and then connect the mains voltage.

Electronic call

When power is applied to the circuit, a sound signal is heard, very similar to a bird's trill. Power is supplied through the bell button. Power source - 9V battery. The DC operating mode of the transistor is set by resistor R1. Generation depends on C1 and C2, as well as the inductance of the primary winding of the transformer. The transformer was taken as a ready-made output from an old transistor receiver “Yunost”. In principle, a transformer from any transistor receiver with a push-pull transformer ULF is suitable. Any speaker.

Krivlov P. Journal Radioconstructor No. 12-2015

Musical call

This device is the simplest and most economical of all those published in the literature. Basically, such a bell is intended for use as an apartment bell, although it can also find other applications, for example in toys or as an alarm clock bell.

The circuit is based on the BT66T-2L music synthesizer microcircuit (Fig. 1). Inside it has an RC oscillator and a melody generator, which consists of 127 notes and repeats periodically. Elements C1, R2, VT1, VT2 set the sound operating time, and VT3 is the power amplifier. The last transistor is installed only if you need to increase the volume of the sound emitter (BA1 can be connected directly to the output of the synthesizer, as shown by the dotted line).

Rice. 1. Electrical circuit of a musical bell

After pressing the SB1 button, the time the signal sounds depends on the capacitance C1 and the resistance R2 (with the values ​​​​indicated in the diagram, it is approximately 2...3 s). If desired, you can increase the playing time by increasing C1.

Power is supplied from two 1.5 V galvanic elements. In standby mode, power consumption is almost zero, since all transistors are in the off state (will be equal to the leakage current of capacitor C2), so a switch is not required.

Rice. 2. Topology printed circuit board and arrangement of elements

To install elements you can use printed circuit board, shown in Fig. 2. Any details will do.

Malyshev S.Yu. Mariupol

Touch room bell

The diagram of the touch-sensitive apartment bell is shown in Fig. 1.

The B1 bell will turn on when you touch the E1 sensor contact, which can be any conductive object electrically isolated from the ground.

When you touch the sensor contact E1, the voltage induced at the base of the transistor VT1 opens it, causing the opening of transistors VT2 and VT3. In this case, bell B1 beeps.

The touch-sensitive apartment bell circuit uses high-voltage transistors, and resistor R1 must have a power of at least 1 W.

Attention! When setting up the device, you must remember that its elements are under hazardous conditions. mains voltage!

From the site http://radiolub.ru

Scheme of a touch doorbell on a microcircuit

Transformer T1 is the output transformer from a small transistor radio. Dynamic head BA1 with a power of 0.05-0.5 W with a voice coil with a resistance of 4-50 Ohms.

Power source - Krona, Corundum battery or two 3336 batteries connected in series. The sensor element can be made from foil PCB. Distance between contact pads should be 1.5...2 mm, and the gap between them should be protected from dirt and moisture with varnish or paint. The shape of the contacts of the sensor element can be any.

Setting up a call comes down to selecting capacitor C1 to obtain the required tone of the sound signal for a specific design of the sensor element.

Rice. 1. Scheme of a touch-sensitive doorbell (a) and its circuit board (b)

I.A. Nechaev. Mass Radio Library, Issue No. 1172, 1992.

Simple doorbell

There are situations when there is a need for a simple doorbell that has sufficient volume and contains a minimum of details. Doorbell circuit shown in the figure, consists of a transformerless power supply with a quenching capacitor C1 and simple generator audio frequencies collected on transistors VT1 and VT2. Resistor R2 serves to limit the peak current through the bridge diodes VD1...VD4. To start a call, press the SB1 button. A device correctly assembled from serviceable parts does not require adjustment. Capacitor C1 is used type MBGCH, K42-19, K73-17, K78-4. Instead of the transistors VT1 and VT2 indicated in the diagram, you can use transistors of the type MP40, MP41, MP42 And MP36, MP38 respectively. The dynamic head BA1 should have a power of 1-3 W, like 1GD36, 1GD40, 2GDSh9, ZGDSH1. From the site http://radiopill.net

Homemade call based on a subscriber loudspeaker

The proposed device is made on the basis of a conventional broadcast loudspeaker, contains a minimum of parts and is capable of delivering a fairly strong sound signal, since the emitter is a speaker. This bell is powered from an autonomous low-voltage source (battery). The device does not consume energy in standby mode and is absolutely safe.

Fig.1. Schematic diagram of a homemade call based on a subscriber loudspeaker.

Due to the small number of parts, there is no point in making a printed circuit board. Installation is carried out using a hinged method. The terminals of the speaker, transformer, and 68-kilo-ohm potentiometer are used as supports for soldering.

Base speaker volume control - R1 on base electrical diagram performs the function of adjusting the pitch of the generated signal, which can be set at will. The switch (toggle switch, button or other contact connector) is placed in a convenient place at the entrance to the entrance, section on the floor or front door apartments.

Any of the low-power germanium MP39 - MP42 is suitable as transistor VT1. The choice of resistor R2 is equally uncritical; the most common VS, MLT, ULM with a rated power of 0.125 W or more are suitable. Capacitor - any type. Elements R1, T1 and BA1 are from the broadcast loudspeaker.

It happens that a correctly assembled bell does not work when the power is connected. Then you should swap the ends of one of the windings of transformer T1. However, the lack of generation at the audio frequency may also be a consequence of substandard transistor VT1. In this case, you will have to replace it with another one that has a higher gain.

If the pitch adjustment range of potentiometer R1 is not satisfactory, then it can be easily changed by selecting the capacitance of capacitor C1. But the sound of this call also depends on the supply voltage. By changing the pitch of the bell, you can also judge the degree of discharge of the power source and promptly change a worn-out galvanic cell or battery. Just remember to maintain polarity, because the transistor does not tolerate polarity reversals.

V. Besedin, Tyumen

Diagram of a call with the sound of Big Ben

This sound effect can be created in circuitry using two timer chips.

The first oscillator is tuned to a frequency of 1 Hz, and the second is modulated by a changing signal from the output of the first. The frequency of each generator can be changed by resistances R1 and R2. Resistor R1 can be used to regulate the speed of switching from one tone to another, and resistor R2 can regulate the tone of the sound signal. The speaker is designed for an impedance of eight ohms.

Nowadays there are a wide variety of low-power communication devices on sale that are available without registration, such as VHF pocket radios, radio-controlled toys, and recently radio alarms have also appeared. In general, the amateur radio design is very interesting in terms of its breadth of application. It consists of two blocks - a remote control button and the signaling device itself.

A relay is connected to the anode of the thyratron, for example RES6), the rear contacts of which are connected in parallel to the contacts supplying a regular doorbell. To protect against false alarms of the sensor and ignition of the thyratron, it is used parametric stabilizer, built on a zener diode VD1 and ballast resistance R3.

The sensor is made of aluminum rivet, the resistance R1 and the thyratron are located in a small housing. To indicate the activation of the sensor, a hole is made in the housing opposite the thyratron. When you touch the “rivet” the thyratron will flash brightly. Adjusting the touch device circuit consists of installing variable resistance R5 voltage 170 V oxide capacitor at a minimum mains voltage, such voltage can be supplied using an autotransformer. The design is borrowed from No. 6 1990.

The design consists of a control generator, on elements D1.1-D1.3 digital IC K155LAZ, generating control pulses, the frequency of which is determined by the nominal value of capacitance C1 and resistance R1

At given ratings, the generator switching frequency is 0.7...0.8 Hz. Pulses from it are sent to tone generators and, in turn, connect them to a ULF assembled on a transistor. The first generator is built on elements D1.4, D2.2, D2.3 and generates pulses with a repetition rate of 600 Hz, the second generator consists of D2.1, D2.4, D2.3 and operates with a frequency of 1000 Hz, which is regulated by selecting the SZ , R3. The sound volume is adjusted by R5.

The design is easy to assemble and adjust. The basis is three master sawtooth voltage generators, each of them operating at its own frequency.

F=1/(2C1R2ln(1+2R3/R1))

where C1 is in farads, R1, R2, R3 is in ohms. The signals from the output of all three generators are mixed and sent to an amplifier, which is loaded into an eight-ohm load.

The first design replaces the door bell, and is triggered when the door is opened, reacting to even a slight change in its position, while the other eliminates the question of connecting it

Limiting the time the doorbell sounds

As you know, they are turned on by a button at the door and work as long as the button is pressed. If the button is accidentally shorted, which happens when it is made from low-quality plastic, or it is specially shorted, for example, with a match, then the bell will work continuously. The call is not designed for this mode of operation. At best, it will burn, and at worst, a fire is possible.

When the caller holds the button down for a long time, the long ringing gets on the nerves, so it is advisable to limit the sound time to 5-7 seconds. The time limit design described below allows this to be done.

This is how the circuit works. When you press the SB1 button (at the door), voltage is supplied through the normally closed contacts K1.1 to the bell. It starts to sound. At the same time, voltage is supplied to the chain R1, VD1, K1, C1. Initially, C1 represents a short circuit for current limited by resistor R1. Capacitor C1 begins to charge through R1, VD1. After a few seconds, C1 will charge to the operating voltage of relay K1. The relay is activated, contacts K1.1 are opened and the bell is disconnected from the network. When the SB1 button is released, capacitor C1 is discharged through the relay coil K1. When the voltage on C1 becomes less than the release voltage of relay K1, it will return to its original state, contacts K1.1 will close and you can call again. By selecting R1 and C1 you can adjust the sound time of the signal.

Scheme of one bell for two doors

If an apartment or house has two entrances, it is not always clear where the call is coming from. This design will save us from this drawback. When button S2 is pressed, the relay is self-locking. At the same time, the second indicator lamp lights up. The bell will ring until the capacitance C1 is charged to the supply voltage level. If the signal needs to be reapplied, S2 is released and C1 is discharged through the winding. Lamp H2 continues to light until S3 is open.

If guests press the S1 button, the bell sounds in parallel with the H1 indicator lamp turning on. The duration of the sound is one second, the pause is 2 seconds.

Here are diagrams for beginners, radio amateurs, recommended for a successful start.

When assembling the proposed circuits, pay special attention to the serviceability of the radioelements used!!!

Description of the circuit

This circuit is the simplest single-ended multivibrator, which causes the LED to glow intermittently. The LED flash frequency is determined by the multivibrator generation frequency. When the power source is turned on, the collector current of transistor VT 2 will change abruptly from zero to the initial value, which is determined by resistors R 1, R 2 and the coefficient h 21e of transistors VT 1, VT 2. The strength of the initial collector current VT 2 is set by selecting resistor R 2, with capacitor C 1 disconnected. In this case, the LED should not light up yet. The selection begins with the resistance values ​​R 1, at which the LED lights up, then the resistance R 1 is increased until the LED goes out. By selecting capacitor C 1, the required blinking frequency is achieved. Resistor values ​​may differ from those indicated in the diagram by +, - 10%. Low-power transistors of the MP group, instead of MP41, you can install MP39, MP42, with any letter index. In place of MP37 you can put MP10, MP38. You can use any commercially available LED. The circuit has been repeatedly tested for functionality and, if assembled correctly, starts working immediately. This circuit can be used as an alarm device, or as an emitter of an alarm device in a car and at home.

Description of the circuit

This circuit is a symmetrical multivibrator, the frequency of which depends on the values ​​of capacitors C1, C2, as well as on resistors R 1, R 2. The frequency of alternate blinking of the LEDs, respectively, depends on the frequency of the multivibrator, which in turn can be changed by selecting capacitors C1, C2 and resistors R 1, R 2. Transistors VT 1, VT 2, MP groups and can be MP39, MP40, MP41, MP42, with any letter index. LEDs can be anything except infrared. The circuit is easy to manufacture, has been repeatedly tested for functionality and, if assembled correctly, starts working immediately when power is applied. Apply this scheme Can be used as a light indication element in various devices.

Description of the circuit

The generator begins to operate at a voltage of several tenths of a volt, even with a transistor with a low static coefficient. Generation occurs when button S1 is pressed, due to the action of strong positive feedback between the collector and the base. R1 sets the desired volume and tone of the sound. Transformer T1 - from any transistor small-sized radio receiver. Any high-impedance telephones of the TM-2A type can be used as headphones; in extreme cases, a capsule of the DEM-4M type will also work.

Description of the circuit

When you press button S 1, capacitor C1 is charged. Capacitor C1 is discharged through a voltage divider on resistors R 2, R 3 connected to the base circuit of transistor VT 1. Since the voltage on capacitor C1 drops as it is discharged, the bias voltage at the base of transistor VT 1 decreases, resulting in a change in frequency sound. A sound reminiscent of a serena's howl is heard from the dynamic head. Transistor VT 1 can be replaced with KT315, KT3102 with any letter index. Transistor VT 2 can be replaced with KT837 with any letter index. When assembling the circuit, pay special attention to the correct connection of the button. Despite the simplicity of the circuit, for some reason, it is the connection of the button that is often confused; as a result, serenading does not simulate, but only a normal sound tone of a certain frequency is heard. The circuit has been repeatedly tested for operability, and with the ratings of the radio components indicated in the circuit and error-free assembly, it begins to work immediately.

Description of the circuit

The bell consists of two generators, a tone generator made on transistors V 3, V 4 and symmetrical multivibrator V 1, V 2. As is known, when a multivibrator is operating, its transistors alternately close and open. This property is used to control the frequency of the tone generator. The output of the multivibrator is connected to the tone generator through resistor R 5, so it will periodically be connected to the common wire (to the plus of the power source), i.e. parallel to resistor R 7. In this case, the frequency of the generator will change abruptly; when the transistor from the dynamic head B 1 is closed, the sound of one tone will be heard, and when open, another tone will be heard. Capacitors C2, C3 protect the multivibrator from pulses penetrating from the tone generator. In the absence of capacitors, the frequency of the multivibrator will change, which will lead to the appearance of unpleasant tones in the ringing sound. In place of those indicated in the diagram, you can use any other low-power low-frequency germanium transistors of the appropriate structure. Capacitors may differ from the nominal value indicated in the diagram by +.- 10%. Any dynamic head B1, with a power of 1-2 W. and a voice coil DC resistance of 4-10 Ohms. In place of capacitors C2, C3, you can install one electrolytic non-polar capacitor of 1.2 microfarads. on Rated voltage not lower than 6v. The bell parts can be mounted on a printed circuit board made of foil getinax or fiberglass. The circuit has been repeatedly tested for operability; with the ratings of the radioelements indicated in the circuit and error-free assembly, it does not require adjustment.

PCB drawing

Telegraph simulator on IC K155LA3

Description of the circuit

The proposed telegraph simulator is quite simple to manufacture and is intended for independent study of the telegraph alphabet. The S1 button is a mechanical telegraph key. The device consists of 4 2I elements - NOT the K155LA3 microcircuit. Elements DD1.1, DD1.2, DD1.3 form a pulse generator with a frequency of 1000 Hz. Element DD1.4 is a buffer. Using resistor R1, the frequency of the generator is adjusted. The power source can be a low-power 5V power supply.

Simple adjustable block nutrition

Transistor designs require power for their power supply. constant pressure a certain value, 1.5V, 3V, 4.5V, 9V and 12V. To avoid wasting money on purchasing galvanic cells and batteries when checking and setting up assembled circuits, use a universal power supply powered by AC mains and allowing you to obtain any constant voltage. The diagram of such a block is shown in the figure. His output voltage can be smoothly changed from 0.5 to 12 V. Moreover, it will remain stable not only when the mains voltage changes, but also when the load current changes from several milliamps to 0.3 A. In addition, the power supply is not afraid of short circuits in the load circuit , which are not uncommon in the practice of radio amateurs.

Let's take a closer look at the operation of the power supply. It is connected to the network using a two-pole plug XP1. When the contacts of switch SA1 are closed, the mains voltage is supplied to the primary winding of the step-down transformer T1. An alternating voltage appears at the terminals of the secondary winding, significantly less than the mains voltage. It is rectified by diodes VD1 - VD4, connected in a so-called bridge circuit. In order for the rectified voltage to be as stable as the voltage of the battery of galvanic cells, the output of the rectifier is electrolytic capacitor C1 large capacity. The rectified voltage is supplied to several circuits: R1, VD5, VT1, R2, VD6, R3; VT2, VT3, R4, (R2, VD6) is a zener diode with a ballast resistor. They make up a parametric stabilizer. As we said above, regardless of fluctuations in the rectified voltage, there will be a strictly defined voltage on the zener diode VD6, equal to the stabilization voltage of this type of zener diode (in our case from 11.5 to 14 V). A variable resistor R 3 is connected in parallel with the zener diode, with the help of which the desired output voltage of the power supply is set. The closer the resistor slider is to the top terminal, the greater the output voltage. From the variable resistor motor, voltage is supplied to the amplifier stage assembled on transistors VT2 and VT3. We can think of it as a power amplifier that provides required current through the load at a given output voltage. Resistor R5 simulates the load of the power supply when nothing is connected to the XT1 and XT2 terminals. The voltage on it is almost equal to the voltage between the variable resistor motor and the common wire (XT2 terminal). To be able to control the output voltage, a voltmeter consisting of a microammeter and additional resistor R 6.

Note: Rectifier diodes, diode bridge VD1 - VD4 can be replaced with more modern type KD226 which are designed for a reverse voltage of more than 250V or imported analogues. Transistors VT1, VT2 can be replaced with KT361 or imported analogues. The VT3 transistor can be replaced with a KT837 with any letter, which will even facilitate its installation on the heat sink. A duralumin or aluminum plate 2mm thick, 40mm wide, 60mm high is suitable as a heat sink. The installation of radioelements is carried out on a printed circuit board made of fiberglass, although there are examples that for starters circuit board made of thick cardboard. The entire structure is placed in a housing made of dielectric material (plastic, plastic, etc.).

Mounting transistor VT3 on the heat sink.

When assembling you need to be careful and careful because... here on the primary winding of the transformer there is a life-threatening voltage of 220V.

Scheme of a transformerless push-pull ULF

Description of the circuit

A simple transformerless push-pull amplifier with a power of 1.5 W. The high-frequency transistor P416 is used here for the reason of reducing the noise of the input stage as much as possible, because in addition to being high-frequency, it is also low-noise. In practice, it can be replaced with MP39 - 42, with a deterioration in noise characteristics, respectively, or with silicon transistors KT361 or KT3107 with any letter.. To prevent step-type distortion, a diode VD1 - D9, with any letter, is connected between the bases of VT2, VT3, and the phase inversion cascade, due to which a bias voltage is formed at the bases of the transistors. The voltage at the midpoint (the negative terminal of capacitor C2) will be equal to 4.5V. It is installed by selecting resistors R2, R4. The maximum permissible operating voltage of capacitor C2 can be 6V.

Melodious call for a landline phone. Call pattern

Call on MC34017 for phone, door, devices...

Not all landline telephones have beautiful and melodious calls. If your phone has a sharp and loud ring, and some copies still have mechanical ones with cups, then you can fix this. Using the simple scheme below, assemble a beautiful melodic bell on one MC34017.

A loud and sharp telephone call that occurs without any warning greatly distracts from the train of our thoughts, and can generally frighten us :) A very quiet call is also bad - you can’t always hear it.

The circuit diagram of a telephone call on the MC34017 chip presented below allows you to get out of this situation!

A beautiful melodic and moderately loud call - a sequence of melody from two mixed frequencies will invite you to the phone :)

There are three types of microcircuits:

• MS34017 -1 (1000 kHz) C2 - 1000 pf;
• MS34017 -2 (2000 kHz) C2 - 500 pf;
• MS34017 -3 (0.5 kHz) C2 - 2000 pf.

Sample printed circuit board and arrangement of elements on it

Block diagram of the MC34017 chip

To connect the bell-trill circuit, you first need to disassemble the telephone set and disconnect the electric bell. It can be separate or built into the main board.

In the first case, we unsolder or unscrew the connecting wires suitable for the electric bell coil.

In the second case, we unsolder the two wires going to the piezoelectric element from the board and solder them to our board.

Please note that the circuit is compact and can easily be placed anywhere on the telephone in the place where the electric bell is normally located.

By changing the capacitance of capacitors C2 (high-frequency tone) and C3 (low-frequency tone), you can adjust the desired timbre of the ringing melody. And by changing the capacitance of capacitor C4 - the duration of the call.

This circuit can be used not only for a telephone call, but also for a bell installed at the entrance doors of your house, apartment or maybe room, and also as an indicator for a malfunction, warning, or accident of any kind. electronic devices. To carry out this action, power is required for the circuit - an alternating voltage of 40 - 60V. Disconnect the power supply with a button installed at the door (if used as a doorbell). If you reduce the capacity of C1, you can connect it to a ~220V network. BUT IN THIS CASE BE CAREFUL - THE CIRCUIT AND THE BUTTON WILL BE UNDER LIFE-DANGEROUS VOLTAGE!

Zotov A. Volgograd region.

P O P U L A R N O E:

>>

SHARE WITH YOUR FRIENDS:

Popularity: 2,941 views.

www.mastervintik.ru

Scheme of a simple melodic bell for an apartment

September 16, 2012 by admin Comment »

A simple melodic call for an apartment, the diagram of which is shown in Fig. 16.3.0, contains a minimum number of parts and can be assembled by any radio amateur with a little knowledge of a soldering iron. The sound (frequency of generated oscillations) of the bell is selected by rotating the axis of the variable resistor Rl and changing the capacitance of the capacitor C1. Instead of the transistors indicated in the diagram, you can use similar low-power germanium or silicon transistors.

Rice. 16.3. Schematic diagrams of electronic calls:

a) a simple melodic call;

b) touch call;

c) design of a touch bell based on a variable resistor

The dynamic head BA1 can be anything. The call can be powered from the network or a galvanic battery. The bell parts are assembled on a mounting plate secured in a suitable sized plastic box. The dimensions of the box must be such that it can accommodate the power source and the electrodynamic head available to the amateur. You can turn on the call either from a regular button or from touch contacts. The diagram of the touch version of the call is shown in Fig. 16.3.5. The multivibrator starts to work, that is, the bell rings when the touch contacts E1 and E2 are touched with a finger. At this moment, between the collector of transistor VT2 and the base of transistor VT1, the resistance of the skin of the finger turns on, and positive feedback appears between the cascades.

Touch contacts are two metal rings of different diameters, which are located one inside the other. The rings are cut out of a sheet of thin copper or brass foil and glued in a certain way onto a small plastic plate. After this, the wires going to the bell are soldered to the metal rings, and the plate is secured in a convenient place near the door. An unusable variable resistor, for example, type SP-1, can be used as touch contacts. The resistor cover and the axis with the slider are removed, and the remaining part is fixed in place of the bell button, Fig. 16.3.v.

Literature: V.M. Pestrikov. Encyclopedia of amateur radio.

nauchebe.net

E-call | Electrician in the house

To call, attract attention, or ring the doorbell, various sound and light signals are used. Previously, these were ordinary bells, then electric bells, electromagnetic bells. Nowadays, melodious electronic bells or electronic bells that play melodies, imitate the voices of birds, etc. are increasingly installed for calling and as doorbells. In this article we will look at several simple electronic calling schemes that you can make yourself.

Single tone electronic calls

The diagram shows:

• R1 - resistor MLT-0.5, 10 kOhm
• R2, R4 - resistors MLT-0.5, 2.2 kOhm
• R3 - resistor MLT-0.5, 91 kOhm
• S1 - button A1 0.4-127
• VT1, VT2 - transistors GT109Zh
• VT3 - transistor GT402I

The diagram shows a call using a multivibrator on bipolar transistors. Bipolar transistors (in the diagram VT1 and VT2) are components of the electronic circuit of the multivibrator. After the S1 button is pressed, the transistor pair (multivibrator) becomes a source of electrical oscillations of sound frequency, which are then transmitted to the reproducing device - the speaker. The frequency of the reproduced sound vibrations in the speaker is equal to the frequency of the multivibrator.

Doorbell of one tone with the ability to adjust the audio frequency of the signal

The diagram shows:

• R1, R4 - resistors MLT-0.5, 5.6 kOhm
• R2, R3 - resistors MLT-0.5, 62 kOhm
• R5 - trimming resistor SP3-38B, 47 kOhm
• C1, C2 - capacitors K50-35, 10 µF, 25 V
• S1- button A1 0.4-127
• VT1, VT2 - transistors GT109Zh
• VT3 - transistor GT402I
• B1 - speaker 0.5GD-17 (8 Ohm)

The figure suggests a similar circuit for an electronic bell based on an oscillation modulation circuit consisting of two bipolar transistors VT1 and VT2, which is activated after pressing the button. The circuit is powered by a voltage of 9 V. The fundamental difference with the previous circuit is that thanks to a resistor with variable resistance (potentiometer), you can manually set the frequency of reproduced oscillations through an audio speaker connected to the collector of the VT3 transistor. The disadvantage of this circuit is the monotony of the frequencies of sound vibrations induced by the multivibrator.

Electronic bell operating at different voltages

The diagram shows:

• R1, R3 - resistors MLT-0.5, 2.4 kOhm
• R2 - resistor MLT-0.5, 100 kOhm
• C1, C2 - capacitors K73-17, 4.7 µF, 63 V
• VT1, VT2 - transistors GT109Zh
• VT3 - transistor GT402I
• B1 - speaker MRP 28N-A, 100 Ohm

The figure shows a diagram of an electronic bell, the operating principle of which is based on the use of different voltage values. The basis of the electronic bell multivibrator circuit consists of two bipolar transistors (in the circuit VT1 and VT2), this is structurally similar to the circuits presented earlier. While the potential difference is insufficient, the transistor is closed, as soon as the voltage is within the desired value at the XT1 terminals, then the transistor opens to allow current to flow and the speaker turns on.

Circuits of electronic doorbells with a complex sound signal

Bim-bom doorbell

If you are not satisfied with the monophonic sound of the doorbell, then you can install the electronic circuit shown in the diagram below, creating a “bim-bom” type sound of the bell. The operating principle of this circuit is based on the operation of a transistor multivibrator. Unlike previous schemes, this one allows you not only to create sound vibrations of various frequencies, but also to set the rhythm and pause time between the sound signals of the electronic call.

The diagram shows:

• T1 - step-down transformer TA-2-127/220-50 (pins 3 and 4 (~7V))
• S1 - button A1 0.4-127
• D1-D5 - diodes D226
• C1 - capacitor K50-16, 1000 µF, 16V
• C2, C3 - capacitor K50-16, 10 µF, 16V
• R1, R2 - trimming resistors SP3-38B, 470 kOhm
• R3, R6 - resistors MLT-0.5, 10 kOhm
• R4, R5 - resistors MLT-0.5, 33 kOhm
• R7 - resistor MLT-0.5, 1 kOhm
• R8 - resistor MLT-0.5, 470 Ohm
• VT1, VT2, VT3 - KT630D transistors
• VT4 - transistor KT630G

On schematic diagram The multivibrator circuit is formed using bipolar transistors VT1 and VT2. The frequency of formation of rectangular pulses is set using resistors with variable resistance (potentiometers) R1 and R2. Also by changing the resistance of adjustment resistors R1 and R2, you can set the pause time and sound duration of the signal transmitted to the playback speaker; in our case, the sound duration can reach from three seconds to creating a continuous sound of the outgoing audio signal.

This circuit is based on a multivibrator using bipolar transistors, in which rectangular pulses of audio frequency are generated. The resulting pulses passing through the repeater on the emitter of the bipolar transistor VT3 enter the cascade of the transistor VT4 and at this moment the circuit is closed and the bell makes a sound - “bim-bom”. In more detail, the principle of creating a sound signal of different tonality and sound can be described in this way: after pressing the button S1, transistor VT3 is open to allow current to flow to transistor VT4. This creates the basis for the occurrence of electrical impulses in the multivibrator, which are transmitted to the reproducing speaker and create audio frequency oscillations in it. Let's call this signal primary. If transistor VT2 is open, then transistors VTZ and VT4 are locked accordingly. This creates a situation where the bell circuit is broken, at which point the multivibrator generates a sound signal of a different frequency and tone. The duration of pressing the bell button also affects the frequency of the generated sound vibrations. To avoid excessive potential differences in the circuit, as well as inductive amplitude voltage fluctuations, the circuit Diode D5 is built-in, which also ensures safe operation of transistor VT4.

Electronic doorbell with triple tone alarm

The diagram shows:

• S1, S2, S3 - buttons A1 0.4-127
• D1 - zener diode D814V
• D2 - zener diode D816A
• D3 - zener diode KS468A
• D4 - diode D226G
• R1 - resistor MLT-0.5, 5.1 kOhm
• R2, R4, R7 - resistors MLT-0.5, 4.7 kOhm
• R3 - resistor MLT-0.5, 2.4 kOhm
• R5, R6 - resistors MLT-0.5, 120 kOhm
• R8 - resistor MLT-0.5, 820 Ohm
• R9 - resistor MLT-0.5, 560 Ohm
• C1, C2 - capacitors K73-17, 4.7 µF, 63 V
• VT1, VT2 - transistors KT630G
• VT3, VT4 - transistors GT402I

Schematic diagram of an electronic doorbell, which simulates oscillations of sound frequencies of several tones, using a multivibrator assembled on bipolar transistors. By varying the pressing of the S1, S2 and S3 buttons in the multivibrator, current pulses are generated, which, when transmitted to the playback speaker, create oscillations with a frequency of 2.0, 1.0 and 0.3 kHz.

These circuits are fundamentally simple to design and install, and therefore will not cause any difficulties even for novice radio amateurs. An item assembled with your own hands is always valued higher than something bought in a store, so create, invent, try. In addition, by selecting ohmic resistance or parameters of bipolar transistors, you can achieve a unique sound for electronic doorbell models.

elektricvdome.ru

Notes for the master - Electronic doorbells

Code call

In the circuit in Fig. 1, a two-tone generator is used as a code call. Now loved ones who know the bell code announce their arrival with a melodic sound, and those who do not know the code - with a single-tone signal.

The bell consists of four multi-contact buttons (the author used a P2K switch with a remote lock), which are fixed near the front door.

The position of the contacts of the button block corresponds to code 1010. In standby mode, the bell is de-energized, and the base of the transistor VT1 is connected to the collector through the closed contacts SB1.1, SB3.1 of the SB1 and SB3 buttons.

When these buttons are pressed simultaneously, power is supplied to the bell through the closed contacts SB1.2 and SB3.2, and the open contacts SB1.1 and SB3.1 break the circuit connecting the collector and the base of transistor VT1. As a result, this transistor periodically (with the pulse repetition rate of a low-frequency oscillator assembled on elements DD1.1 - DD1.3) opens and supplies power to the second generator - a tone generator on elements DD2.1 - DD2.4. In this case, the dynamic head BA1 emits a frequency-modulated signal.

When other buttons are pressed in any combination, the base and collector circuits of transistor VT1 are closed and the dynamic head reproduces a single-tone signal, since frequency modulation not happening.

It is not necessary to code the SB1 and SB3 buttons. You can code three or one button. It is important that their first contacts work to open.

Sinkov D.

Lugansk

Two-tone electronic call

It can be assembled on just one chip and one transistor (Fig. 2), and use a capsule as the BF1 emitter

TA-4. The peculiarity of this capsule is that it has a resonant frequency at which the sound volume increases sharply. Therefore, when connecting even a weak signal, you can achieve a clearly audible sound.

Built on the K176IE5 chip two tone generator. Its fundamental frequency depends on the resistance of resistor R3 and its capacitance of capacitor C1, and the modulation depth depends on the resistance of resistor R1. The transistor stage acts as a power amplifier, necessary to match the high-resistance output of the microcircuit with a relatively low-resistance load - the BF1 capsule.

The bell is powered by a somewhat unusual rectifier, which includes a limiting resistor R4, rectifier diode VD1, zener diode VD2, LED HL1, capacitor C1. Until the SB1 bell button is pressed, the capacitor is charged to a voltage equal to the sum of the stabilization voltage of the zener diode and the voltage drop across the lit LED. In this case, the capacitor becomes a battery of electricity.

When the SB1 button is pressed, the voltage from the capacitor is supplied to the two-tone generator and power amplifier. A sound is heard from the capsule, the duration of which depends on the capacitance of capacitor C2. After releasing the button, the capacitor begins to charge again, which takes a few seconds. Moreover, the LED is switched off at the initial moment and begins to glow only when the voltage on the capacitor reaches the stabilization voltage of the zener diode and current flows through it.

When setting up a call, first turn off resistor R1 and select resistor R3 (for this purpose, it is advisable to temporarily replace it with a variable resistor with a resistance of 510 kOhm) to achieve the highest volume of the capsule sound (of course, with the contacts of the SB1 button closed). After this, connect resistor R1 and select it (if necessary) to set the desired modulation depth, in other words, the sound of the second tone.

Both during setup and final installation of the bell, ensure that the phasing of the connection of the bell wires to the lighting network is observed.

Zarubin A.

Karatau

Intermittent Signal Generator

The intermittent sound signal generator (Fig. 3) consists of two interconnected multivibrators in which all four logical elements of the K155LA3 microcircuit operate.

The multivibrator on elements DD1.3 and DD1.4 generates oscillations with a frequency of about 1000 Hz, which are converted by the telephone capsule BA1 into sound. But the sound is intermittent, because the operation of this multivibrator is controlled by another one - on logic elements DD1.1 and DD1.2. It generates clock pulses with a repetition rate of about 1 Hz. The telephone capsule sounds only during those periods of time when the output of the clock generator appears high level voltage. The duration of sound signals can be changed by selecting capacitor C1 and resistor R1, and the pitch of the sound by selecting capacitor C2 and resistor R2. Such a device can completely replace a regular apartment bell.

Borisov V.G.

The simplest touch call

The touch device can be used for a regular electric bell, Fig. 4.

In this case, there is no need for an electric button. When entering an apartment, a sound signal is heard at the moment a finger touches a sensor contact electrically isolated from the “ground”. The alarm is powered from the mains and does not consume any current in standby mode. It contains an amplifier using transistors VT1...VT3, a diode bridge VD2...VD5 and a bell HA1. When you touch the sensor contact E1, a weak leakage current flows through the base circuit of transistor VT1, and the transistors open at negative half-cycles of the network. In this case, the HA1 bell beeps. Diode VD1 conducts positive half-cycles of the leakage current.

The signaling device can only use high-voltage transistors with a permissible voltage between the collector and emitter of at least 300 V. The static current transfer coefficient of the transistors must be at least 25. The VT3 transistor can be of medium power, but provided that it is installed on a radiator that allows dissipation power 3…4 W. The bridge diodes must be designed for a reverse voltage of at least 400 V, for example, D226B. Call NA1 is a network call, for a voltage of 127...220 V, for example, EP 127-220 V. To ensure safe operation of the device, resistor R1 must have a resistance of at least 2.2 Megohms and a power of at least 1 W. With such resistance, the leakage current passing through the human body is not felt at all.

When setting up the alarm device, you must remember that its elements are under mains voltage. By selecting the resistance of resistor R2, the required sensitivity of the device is established. Resistor R2 should not be selected with a resistance of more than 2.4 MΩ, since this will cause the device to operate intermittently.

Pestrikov V.M.

"Radio-electronic devices,

useful in everyday life"

Touch call

When you touch the E1 sensor, which consists of two metal plates, with your finger, the HL1 LED begins to blink and the B1 alarm beeper sounds intermittently, Fig. 5.

Transistors VT1 and VT2 form composite transistor. The input resistance (base) of such a transistor is high. While transistor VT1-VT2 is closed, the voltage on R2 is low, and transistor VT3 is also closed. In order for the composite transistor VT1-VT2 to open, voltage must arise at the base of VT1. When you touch the E1 sensor plates with your finger, an opening voltage is sent to the base through the conductivity of the skin of your finger. The composite transistor VT1-VT2 opens and discharges capacitor C1. The voltage on R2 increases and VT3 opens.

The collector circuit VT3 includes a sequentially flashing LED HL1 and a “beeper” B1 (a sound emitter with a built-in generator). The flashing LED HL1 flashes and B1 makes a sound each time the LED flashes.

After you remove your finger from the E1 touch plates, the composite transistor VT1-VT2 will close, but the touch bell will still blink and sound for some time while the capacitor C1 is charging through R2.

Resistor R1 can have a resistance from 3 to 10 megaohms. The capacitance of capacitor C1 can be from 220 µF to 1000 µF. The flashing LED HL1 type L-7986SRC-8 can be replaced with any other flashing one without a built-in current-limiting resistor.

You can also use a regular indicator LED, but then the lighting and sound will be without interruption.

Electronic touch bell

Figure 6 shows a diagram of an electronic call, or rather a tone signal which, moreover, does not require a button.

Instead, a sensor is used - a touch pad consisting of two separated metal plates. If you touch it, a pleasant tone will be heard in the apartment, and the pitch of the tone depends on how hard you press your hand against the sensor. The stronger the pressure, the less resistance there will be between the power plus and the base of transistor T1. The latter causes a change in the frequency of oscillations produced by the generator on transistors T3, T4.

Power is supplied to the generator through transistor T2, controlled by transistor T1 with a sensor input. As soon as you lightly touch the sensor, transistors T1, T2 will immediately open, transistors T3, T4 will receive power through them, and further generation of the signal will depend on the degree of pressure on the touch pad.

Transistors are used like KT315, KT306, KT301 and others. Any small-sized one is suitable as a dynamic head, for example, type 0.5GD-14, 0.25GD-1. The circuit is placed in any compact case and is connected by two wires to the contacts of the touch pad.

Spot welding diagram

Differential connection diagram circuit breaker

Do-it-yourself chicken coop diagram for 10-20 chickens, photo drawings