Sound module on a single chip. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Radio amateur designer

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In telephone answering machines, chips are often used that allow you to record and repeatedly play phonograms of various sound durations. However, they can be used, for example, as an electronic "watchdog" in your apartment or as a signaling device for reversing a car, or for sounding toys and souvenirs, etc. The author of this article talks about the device of such a sound module and how to work with it.

These microcircuits contain analog-to-digital and digital-to-analog converters, non-volatile random access memory (RAM), a clock generator, a microphone amplifier and a 3-hour output amplifier. In particular, the ISD1416P chip, which is used in the described sound module, can record and play back a soundtrack with a duration of 16 seconds.

The diagram of the sound module is shown in fig. one.

The upper frequency of the audio path bandwidth does not exceed 3,3 kHz. A 3H signal source (for example, a microphone) is connected to pins 17 and 18 of the microcircuit, and to pins 14 and 15 - a miniature dynamic head or a telephone capsule with a resistance of at least 16 m (TEMK-0, for example). The output power does not exceed 3 W.

The output of the microphone amplifier - pin 21 - is connected to the analog input - pin 20 - by the R5C3 circuit. The R19C6 circuit is connected to terminal 6, the values ​​​​of the elements of which determine the characteristics of the built-in AGC system.

Due to the fact that the microcircuit contains digital and analog parts, the penetration of impulse noise into the audio path is possible. To improve noise immunity, the common wires of the digital and analog parts (pins 12 and 13, respectively; they are also negative power leads) should be connected to the device case or the common wire of the module at one point.

The positive power output of the digital part (5 V) is pin 28, and the analog (5 V) is pin 16. Pins 1-6,9, 10 are address inputs A0-A7 of the microcircuit. If the address inputs are not used, they must be driven low.

The built-in clock generator ensures the coordinated operation of all microcircuit nodes. At the same time, it is able to work with an external clock signal as part of complex systems. In these cases, the timing signal is applied to the external synchronization input (pin 26). When working with an internal clock generator, pin 26 must be connected to a common wire.

Pin 25 is connected to a circuit for indicating the mode of recording a phonogram in RAM. The microcircuit switches to this mode, accompanied by the HL1 LED turning on, when a low level is applied to pin 27 with the SB3 button.

In order to listen to the recorded fragment, briefly press the SB2 button. If you use the SB1 button, then the phonogram will sound only as long as its contacts are closed.

Conclusions 7,8,11, 22 of the microcircuit are free, they can be connected to a common wire.

In standby mode, the microcircuit consumes a current of about 1 μA. The guaranteed number of recording cycles provided by the module is 100. It can store the recorded information with the power off for up to 000 years.

The microcircuit is produced in two versions - ISD1416P for mounting in a panel installed on the board or soldering into the board holes and ISD1416S for surface mounting. Both modifications are framed in a plastic case with dimensions of 36,8x13,7 mm and 17,9x7,5 mm with two rows of pins with a pitch of 2,54 and 1,27 mm, respectively.

Switches SB1-SB3 - P2K (two positions, two directions).

If an electret microphone is used to record a phonogram, it is necessary to apply a polarizing voltage to it according to the circuit in Fig. 2a.

In cases where increased requirements are imposed on the sound quality of the reproduced phonogram (no background noise, interference, etc.), the microphone should be connected to the microcircuit through an intermediate differential amplifier. A diagram of one of the options for such an amplifier is shown in Fig. 2b.

To record a complex composite phonogram, its parts must first be processed on a computer using the Sound Forge program, which allows you to enter various sound effects, eliminate insignificant pauses or parts of the phonogram, join several fragments into one block, and much more. The prepared phonogram is entered into the RAM of the microcircuit.

The amplifier is assembled on microassembly transistors VT1. The BM1 microphone was used foreign electret DH9767 with a supply voltage of 4,5 V, an internal resistance of 2,2 kOhm and a working EMF of 12 mV. The DH6050 (1,5 V; 2,2 kΩ; 10 mV) is also suitable. Shielding of microphone circuits is mandatory.

If you intend to use the module in a home bell, the power provided by the microcircuit, of course, will not be enough. On fig. 3 shows a diagram of an additional power amplifier based on the "telephone" chip EKR1436UN1 (foreign analogue - MC34119, Motorola). It is capable of delivering about 1W of power into an eight ohm driver. By changing the values ​​of the elements R1, C1, R2 of the OS circuit, you can choose the best sound quality. To reduce the level of "digital" noise and improve speech intelligibility, the isolation capacitor C1 in the input circuit of the amplifier has a relatively small capacitance. Pin 15 of the DD1 chip of the module must be left free.

When using a sound module on a car (for example, in a reverse gear indicator), you will have to use a more powerful K174UN14 chip.

Power the sound module and the microphone amplifier with a stabilized voltage of 5 V (see Fig. 2). An additional power amplifier, as a rule, requires a higher supply voltage and does not need to be stabilized.

In the case when it is necessary to record a phonogram into the RAM of the module from a microphone, in order to improve its quality, the power supply of the additional 3H amplifier must be turned off for this time. This condition is easiest to fulfill if the power circuit of the DA1 chip in the diagram in Fig. 3 to enter the closed contacts of the second section of the push-button switch, which puts the module into the recording mode (in Fig. 1 this switch is designated SB3).

Both the input and output of the voltage regulator DA1 (see Fig. 2, b) should be shunted with oxide capacitors with a capacity of 10 μF for a nominal voltage of 16 V, mounted near the microcircuit case.

Author: A.Partin, Ekaterinbur

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