Jukebox for the Christmas tree. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

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In addition to the garlands, the Christmas tree can be equipped with an automatic machine that periodically plays your favorite musical fragments or speech greetings. Moreover, there can be several such fragments, and it is possible to replace them with others at any time.

The basis of the machine is a specialized chip of the ISD25XX series, the total duration of fragments, depending on the specific type of chip, can reach two minutes. This chip is a device for recording and playing sound information. The principle of its operation is based on the technology of analog signal storage in multilevel non-volatile memory cells. Recording is done with an electret microphone, and playback is done through a dynamic head. The duration of information storage reaches a century, and the number of record-play cycles is one hundred thousand!

The diagram of the automaton is shown in fig. 7.

Turning on the DA1 chip is standard, and to ensure automatic control mode, a rectangular pulse generator was introduced on the logic elements DD1.1 - DD1 3. The device is powered by a network power supply with a step-down transformer T1, a rectifier on the VD1 diode bridge and an integrated voltage regulator on the DA2 chip. The operating modes are controlled by the switch SA1 and the buttons SB1, SB2. The volume of the signal can be adjusted by the trimmer resistor R1.

The machine works like this. In the state shown in the diagram, pin 27 of the DA1 chip and the power bus of the DD1 chip are connected to a common wire, so the DA1 chip is in the information recording mode, and the generator on the DD1 chip is not working. The HL1 LED is constantly on. Before starting recording, you must briefly press the SB1 "Reset" button so that the microcircuit is installed at the beginning of the signal block being recorded. To record the first sound fragment (speech, music, etc.), you need to bring the machine to the source of the sound signal and briefly press the SB2 "Start / Stop" button. The HL1 LED will go out, which means the signal is being recorded. To end it, briefly press the SB2 button again, the LED will light up. If you record one fragment, then only it will be played.

To record the second sound fragment, at the very beginning of it, briefly press the SB2 button, and at the end of it, press the same button again. So the signals are recorded until the memory of the microcircuit is full, and the filling signal will be the ignition of the LED (after briefly pressing the SB2 button). As mentioned above, the total recording duration is determined by the type of DA1 chip and can be determined by marking. The two or three digits after ISD25 indicate the maximum recording time in seconds.

Playback is carried out automatically when the movable contact of the switch SA1 is moved to the lower position according to the scheme. At the same time, a voltage of +27 V is applied to pins 1 of the DA14 chip and 1 DD5. The DA1 chip will switch to information playback mode, and the generator on the DD1 chip will start working. When a low logic level appears at the output of the DD1.3 element, it will briefly go through the capacitor C10 to pin 23 of the DA1 chip and start playing the first fragment. In this case, the LED will turn off, but will light up again when the fragment ends. The second fragment will start playing when the output element DD1.3 again appears low logic level. This will play all the fragments in turn, and then the cycle will repeat, starting from the first fragment.

The interval between the beginnings of the reproducible fragments is determined by the repetition period of the generator pulses and for the values ​​​​of the elements indicated on the diagram is about a minute. You can change it within wide limits by selecting capacitors C8.C9 and resistor R11.

For a new recording, the SA1 switch is moved to the "Record" position, while the old information is not erased, but is written over it. To start a new recording from the beginning, you must briefly press the button SB1 "Reset". If this is not done, then the recording will be carried out after the fragment that was played last.

Chip DA1 - any of the ISD25 series, but it must be taken into account that the larger the capacitance of the microcircuit, the lower the bandwidth and the worse the signal quality. Based on the maximum bandwidth, ISD2560 is the best, if you need to have a longer recording-playback time, you should use ISD2575, ISD2590, ISD25120. LED - any small-sized with increased light output, the diode bridge can be replaced with separate rectifier diodes with any letter indices.

Oxide capacitors - K50 series or similar imported ones, the rest - K10-17, tuning resistor - SP4, SPO, constants - MLT, S2-33, P1-4. Switch SA1 - any small-sized two-position, buttons - also any small-sized self-returning. Microphone - electret from telephones, its positive output should be connected to resistor R7. The dynamic head can be 0,1-1 W with a voice coil resistance of 16-50 ohms.

As a power source, a mains stabilized power supply (network adapter) for a voltage of 5 V and a current of up to 100 mA or a battery of three galvanic cells connected in series (1,5 V each) or four nickel-cadmium batteries (1,25 V each) is suitable . In this case, the DA2 chip and other parts of the power supply are excluded. If you use an adapter with an unstabilized voltage, then the DA2 chip and capacitor C7 are placed on a separate board inside the device case.

Most of the other parts are mounted on a printed circuit board (Fig. 8) from one-sided foil fiberglass.

The board is placed in a case of a suitable size, on the walls of which buttons, sockets, an LED, a microphone, a dynamic head and a tuning resistor are fixed. To turn off the machine, use the SA2 switch installed in the power supply circuit of the network unit or in the conductor coming from the battery of elements (batteries).

Author: I. Nechaev, Kursk

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