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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Voice alarm. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Automobile. Electronic devices Nowadays, many vehicles are equipped with various alarm systems that usually play a combination of tones when triggered. A device informing the driver in speech form is described here. It can also be used, for example, in a car reversing signaling device, as well as in a house bell, in electronic toys. The voice alarm is applicable in all cases where the storage and multiple playback of small audio files is required. The device (see the diagram in Fig. 1) contains a trigger node on triggers DD2.1, DD2.2, a transistor VT1 and relay K1, a clock generator on logic elements DD1.1, DD1.2 with an inverter DD1.3, a counting node DD3 , DD4, which generates serial addresses for read-only memory with ultraviolet erasure DS1, a digital-to-analog converter DD5 with an op-amp amplifier DA2 and a powerful 3H amplifier DA3. The power supply of the signaling device consists of a voltage regulator DA1 (5 V) and a negative five-volt voltage driver on a transistor VT2 and diodes VD4, VD5 to power the op-amp DA2.
The signal to start the operation of the device is a pulse from the electric interlock of the driver's door lock. For most signaling systems, this pulse has an amplitude of 12 V and a duration of about 0,5 s. Initially, power is supplied only to RS-flip-flops DD2.1 and DD2.2. They do not have preset circuits, so when the supply voltage is applied, the DD2.1 trigger can be in any state. The trigger DD2.2, being in the zero state, will remain in it, and if it is in a single state, then the device completes one cycle and returns the trigger to state 0 by applying a high level to the input R from output 2 of the counter DD4.2. When the central lock is actuated, the impulse from its interlock is fed to the signaling device inputs: when the door is opened - to input 1, and when it is closed - to input 2. When the car door opens, the control pulse switches the trigger DD2.2 to a single state. From the direct output of this trigger, a high-level signal opens the transistor VT1. Relay K1 is activated and through contacts K1.1 supplies power to the DA3 3H amplifier and DA1 voltage regulator. The address counter DD3, DD4, ROM DS1 and DAC DD5 starts working. The C4R6 circuit generates a signal to reset the counters DD3 and DD4, delaying the start of their operation by 0,5 s to establish the operating mode of the device nodes. The clock generator starts producing rectangular pulses with a frequency of 11 kHz. From the buffer element DD1.3 they go to the base of the transistor VT2, which is part of the generator of the negative supply voltage of the op-amp DA2. The high-level signal from the direct output of the trigger DD2.2, going to the lower input of the DD1.4 element according to the circuit, allows the passage of clock pulses to the input of the line of counters DD3.1, DD3.2, DD4.1, DD4.2. At the output of the counters, sequential address signals from 0000 to 1FFF are generated, which are fed to the address inputs of the AO-A12 ROM DS1. Simultaneously with the trigger DD2.2, the trigger DD1 also switches to state 2.1 (if it was in the zero state in the initial state). From its direct output, a high-level voltage is supplied to the address input A13 of the ROM DS1 and sets the most significant bit of the starting address 2000 of the recorded audio file. Thus, the reading of information from the ROM begins in the address range from 2000 to 3FFF. The signals from the outputs D0-D7 of the ROM are fed to the inputs of the DAC DD5. Both the DAC and the op-amp DA2 are included in the standard scheme. The analog signal through the R14C13 filter is fed to the DA3 3H amplifier and, amplified, is reproduced by the BA1 dynamic head. At the end of reading information from the ROM, a high level appears at the output 2 of the counter DD4.2, which puts the trigger DD2.2 in state 0. A low level from the direct output prohibits the passage of the clock pulses of the generator to the input of the counter, closes the transistor VT1, due to which the relay K1 releases the anchor - the device turns off and goes into standby mode. When the car doors are closed, the control pulse from the lock blocker enters the input 2 of the device and switches the trigger DD2.1 to state 0, and DD2.2 to state 1. The device operates in the same way as when the door is opened. The only difference is that the input A13 of the DS1 ROM from the direct output of the trigger DD2.1 receives a low-level signal that sets the most significant bit of the starting address 0000. For this reason, when the door is closed, information from the ROM is read in the address range from 0000 to 1FFF. As a result, the signaling device plays two short messages, one - when the door is opened, the other - when it is closed. For programming the ROM, a file in WAV format 8 bits is formed using any sound editor. The file size depends on the capacity of the ROM and the sampling rate (clocking frequency); at a frequency of 8 kHz - 8 kb / s (voice information), at a frequency of 11 kHz - 11 kb / s (music, speech with high quality). Then, with a file editor that allows you to work with files in the hexadecimal system (most programmers are equipped with such an editor), the 0000D code, which corresponds to a pause, is written to addresses 0039-7, which store service information in the WAV format. After the specified editing, the information is transferred to the ROM, at addresses 2000-3FFF when opening the door and 0000-1FFF when closing. With the elements shown in the diagram, the sampling frequency is 11 kHz, and the device generates two audio fragments with a duration of 0,7 s. The device can use larger capacity ROM chips, for example, 27C256, 27C512. To increase the address space, outputs 2, 4, 8 of the counter DD4.2 are used. Resistors R3-R5 at the input of the signaling device limit the triggering pulse to a level of 6 V. Capacitors C2 and C3 reduce the effect of interference. Capacitors C5, C7 - C10 - filtering in power circuits. It is possible to use the entire capacity of the ROM to play one sound fragment. To do this, the output 2 of the counter DD4.2 is connected to the input A13 of the ROM DS1, and the output 4 is connected to the input R of the trigger DD2.2. Elements DD2.1, R3, VD1 and C2 become unnecessary. The device is assembled on a printed circuit board made of double-sided foil fiberglass 1,5 mm thick. The board drawing is shown in fig. 2. I draw the attention of readers to the fact that almost all transitions from one side of the print to the other are made by soldering the corresponding leads of the parts on both sides. Only one point - it is located near the positive terminal of the capacitor C4 - requires the introduction of an additional wire jumper.
Capacitor C1 should be selected with a small TKE. Oxide capacitors - K50-35, K50-40, the rest - KM, K10-17. Transistors VT1, VT2 are applicable to any of the KT315, KT3102 series. The 27S128 ROM chip can be used with a small number of faulty memory cells, while the sound quality will not noticeably deteriorate. It can be replaced by the domestic analogue K573RF8A. To ensure quick change of sound fragments, a ROM panel should be provided on the board. The DA3 chip operates in a short-term mode, so it does not need a heat sink. Diodes - any of the series KD521, KD522. Relay K1 - RES49, passport RS4.569.501, or any other for a response voltage of 9 ... 12 V. Instead of KR1157EN5V, you can use stabilizers KR1157EN5A, KR1157EN5B, R1157EN5G, as well as KR1157EN501A, KR1157EN501B, KR1157EN502A, KR1157EN502B and foreign 78L05, but taking into account their different pinout (see "Radio ", 1999, No. 2, pp. 69-71). By the way, we note that in some reference publications of recent years, the pinout of the stabilizers of the KR1157EN5 series is given, which differs from that indicated in the Radio magazine. So, the input (pin 17) corresponds to pin 1, the common pin (8) - 2, the output (2) -3. Some alarm systems accompany the opening and closing of door locks with signals from their own annunciator. If it is impossible to turn off these signals, it is necessary to use relay K1 in the signaling device with not one, but with two contact groups (for example, RES60, passport RS4.569.438), and turn off the annunciator with the second group for the duration of the signaling device. The dynamic head BA1 is suitable for any power of at least 2 W and a resistance of at least 4 ohms. The device is mounted in a plastic box and installed behind the instrument panel near the wiper motor. The establishment of the signaling device consists in the selection of resistors R1 and R2, which set the frequency of the master oscillator - 11 or 8 kHz. The setting accuracy should not be worse than 250 Hz. The more accurately the generator frequency matches the sampling frequency of the original, the higher the fidelity of reproduction. The generally accepted sampling standard is 11025 and 8000 Hz. Installation can also be carried out by ear, by comparing the sound of the device with the original. Selecting the resistor R12, set the required playback volume. Author: Yu.Pushkarev
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