Speech programmable signaling device. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Speech programmable signaling device. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Microcontrollers

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Descriptions of electronic speech synthesizers and their use as signaling devices at various objects have already been repeatedly proposed in the radio engineering literature. But the interest of readers in this topic does not weaken. The published article offers two more options for simple devices.

The scheme of the first version of the synthesizer is shown in fig. 1. On the elements DD1.1-DD1.3, a master oscillator is made. With a tuned resistor R2, you can change the frequency of the generator and, accordingly, the tempo and tone of speech or melody playback. The counters DD2 and DD3 enumerate the addresses of the ROM DS1, which contains the digitized audio information.

(click to enlarge)

When the power is turned on, the counters are reset by applying voltage to the inputs R of the microcircuits through the differentiating circuit R1C1. Jumpers S1 and S2 select the bit width of the counters depending on the type of ROM used (the table of positions is indicated directly on the diagram). The simplest digital-to-analog converter is assembled on resistors R3 - R9 and capacitors C4, C5. As practice shows, it is most convenient to use only six digits, discarding the youngest and most significant digits. The fact is that the senior category, as a rule, does not contribute a significant amount of information. And the younger one introduces significant noise into the signal (the so-called sampling noise).

The LM1 chip is used as a power amplifier (DA386). The choice of this chip is due to its small size, ease of use and minimal non-linear distortion. With slightly worse results, you can use other microcircuits, for example, K174UN14 or TDA2003, TDA2030, etc. with their corresponding switching circuits. Variable resistor R15 adjust the playback volume.

On transistors VT1 and VT2, a power control device for the entire signaling device is made. It is possible to work with an autonomous power source (it is shown in Fig. 1) and with AC power. In the latter case, the elements GB1, C3, R10, R12, R13, VT2 should be excluded from the device, and the start button SB1 should be transferred to the primary circuit of the power transformer. The network power supply circuit is shown in fig. 2.

Speech programmable signaling device

When the SB1 button is pressed, voltage is applied to the relay K1 through the transistor VT1, it works and self-locks with one of its contact groups K1.1. At the end of the enumeration of addresses, the pulse from the high-order digit of the counter through the inverter DD1.4 is fed to the base of the transistor VT1. The transistor closes, the relay de-energizes and completely disconnects the device from the network.

The digitized sound signal recorded in the ROM is obtained as follows. A WAV file of 8000 or 11025 Hz MONO format is taken as the source. It is convenient to receive a speech (as well as a musical) signal using the PHONOGRAPH program, which is part of the WINDOWS operating system. The file is loaded into any text editor. As a rule, the first 100-200 bytes are not informative. They contain service information, noise, etc. The file is aligned to the size of the used ROM, removing the first 100 - 200 bytes and the last "extra" non-informative bytes. Next, the edited file is loaded into the programmer and "sewn up" in ROM. You can read more about this in the article by A. Dolgoy "How to write audio data from a WAV file to ROM and "play" them" ("Radio", No. 4, 5, 2001).

As practice shows, for many applications, quite acceptable sound reproduction quality can be achieved using only four digits (in phones with AON, answering machines, etc.). Therefore, using a conventional eight-bit ROM, you can try to write twice as much information. A diagram of such a device is shown in Fig. 3.

(click to enlarge)

The difference between this device and that made in Fig. 1 is an introduction to the DD4 switch circuit. Information is read from the ROM through the switch alternately from the low and high bits of the byte. In all other respects, the operation of the device according to Fig. 3 is similar. The choice of ROM is carried out by jumpers S1 - S3. Of course, for this device, the ROM file must be processed with a special program that "rounds" the data bit length to four and "mixes the nibbles.

In the above diagrams, the order of the address inputs is changed so that the printed conductors on the board are located only on one side. This greatly simplifies the design. However, in this case it is necessary to change the order of recording information in the ROM. Recode the original wav file with special program (it also "mixes" the nibbles for the device in Fig. 3). The file contains examples of already transcoded files, ready to be written to ROM of various sizes. The number 4 in the file name indicates that it is intended for "flashing" the ROM in the device fig. 3, and the number 8 - in the device fig. 1. File extension - their volume in kilobits.

Author: S.Bashirov, Moscow

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