Unusual professions of microchips for watches. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Application of microcircuits

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In electronic watches, specialized microcircuits K176IE5, K176IE12, K176IE18 are widely used, which contain cascades for master oscillators (generator part) and frequency divider counters (connected by internal communication with the generator part). Their switching circuits are given in the article by S. Alekseev "Application of K176 series microcircuits" ("Radio", 1984, No. 4, pp. 25-28; No. 5, pp. 36-40; No. 6, pp. 32-35).

However, a number of useful devices can be built on these microcircuits. First of all, if we abandon the traditional frequency stabilized by a "clock" quartz resonator (32 Hz), they can be used to assemble a precision square-wave generator that can operate in a wide frequency range. Moreover, it must be borne in mind that the maximum pulse repetition rate at which the counters are still stably switched depends on the supply voltage and ranges from 768 (at +1,5 V) to 5 (at +5 V) MHz.

It should be noted that in many electronic devices, high stability of the pulse repetition rate is not at all necessary. They only need to obtain its set value and the possibility of changing within ± 5 ... 10%. In such cases, it is advisable to stabilize the frequency with a circuit that provides long-term stability no worse than 104. If it turns out to be excessive, then these microcircuits can be used to implement a multivibrator with a relative frequency stability of 1 ... 3% when the supply voltage changes from 4-5 to + 12 V. The outputs of the devices will be the outputs of the counter-dividers connected to the generator part inside the microcircuits.

Depending on the microcircuit used, additional elements are connected to the generator part in different ways, as shown in Fig. 1 and 2. Due to the high input resistance of the microcircuits of the "MOS" structure, the quality factor of the connected circuit (Fig. 1) turns out to be quite high, making it possible to obtain a stable generation frequency in LC generators assembled according to the capacitive three-point circuit. It is determined by the parameters of the elements from the expression f = 1 /2nVL1C1C2/(C1+C2) Moreover, the ratio of capacitances of capacitors C1 and C2 for stable generation should be within 2...4.

Ris.1

The large maximum division ratio of the counters ensures the formation of stable oscillations over the entire range of sound frequencies with small dimensions of the circuit coil, so it is not difficult to build, for example, a device for tuning musical instruments on their basis.

The oscillation frequency (below 1 MHz) of multivibrators (Fig. 2) with a resistor R1 resistance of more than 20 kΩ is inversely proportional to the product R1C1, and the proportionality factor depends on the microcircuit sample. A typical frequency value can be determined from the formula

f=2/C1,

where f is in megahertz, C1 is in picofarads.

Ris.2

Devices assembled according to the diagrams in fig. 2 are high accuracy single vibrators. They form single pulses with a duration of 20 ms to tens of hours with an accuracy of no worse than 1 ... 2% with reasonable dimensions of the timing elements. Single vibrators have virtually zero recovery time and can be restarted even before the end of the current output pulse. In this case, it is extended by the full value of the specified duration.

When the device is started, the microcircuit counter counts the pulses of the multivibrator serving as a clock generator until level 15 appears at output 176 (K5IE1) or S176 (K12IE176, K18IE1). As soon as this happens, the multivibrator stops working due to coupling through the diode VD1. Level 1 at the output is held for an arbitrarily long time until the start (reset) pulse sets the entire counter to zero, and the counting starts again. The duration of the generated pulse is equal to 16384 oscillation periods of the multivibrator.

Chip counters K176IE12 and K176IE18 can also be used as distributors of pulses stable in frequency, for example, in control devices for stepper and synchronous motors. Such motors are increasingly used in industrial automation and household radio equipment, in particular in high-quality electric players.

The device, the scheme of which is shown in Fig. 3 provides the necessary switching of current in the windings of a three-phase stepping motor SD-300/300 with a step of 3°. It contains a distribution generator on the DD1 chip and two-stage transistor switches VT1VT4, VT2VT5 and VT3VT6. You can stop the engine in any position by turning on the switch SA1.

Fig.3 (click to enlarge)

The parameters of elements L1, C1 and C2 are determined by the required frequency of steps and are indicated for a frequency of 100 Hz. The maximum step frequency of this electric motor is 250...300 Hz.

The same device can be successfully used to control the electric motor 0-EPU-82SK of the electric player "Radiotekhnika-001" instead of six microcircuits and all other elements of the engine control board. This increases the stability of the frequency of its rotation. To power the device, you can use the +15 V voltage regulator available in the electric player.

In the case of speed control of synchronous motors by changing the frequency of the supply voltage windings, it is most difficult to obtain a constant phase shift between them (usually 90 °). When used for this purpose, a digital current driver provides a phase shift that does not depend on frequency, and does not require the use of large phase-shifting capacitors.

Fig.4 (click to enlarge)

Such a device is implemented according to the scheme shown in Fig. 4, and is designed to replace the TSK-1 electric motor power generator in the Elektronika B1-01 electric player. It consists of a pulse generator-distributor on a DD1 chip and two identical push-pull key power amplifiers on transistors VT1-VT4, VT5-VT8. The form of voltage on the motor windings, shown in fig. 5 differs markedly from the sinusoidal one.

Ris.5

However, due to the inductive nature of the motor windings, the current through them changes smoothly and contains mainly the first harmonic, which creates a torque. The rotational speed of the turntable disc can be changed with the coil trimmer L1. Since power amplifiers operate in key mode, the device has a high efficiency. The output transistors of the amplifiers must be installed on a heat sink with an effective surface area of ​​only 20 ... 40 cm2.

It should be borne in mind that in devices assembled according to the diagrams in Fig. 3 and 4, conclusions 7 and 9 of the DD1 microcircuits must be connected to a common wire.

Author: D. Lukyanov, Moscow; Publication: N. Bolshakov, rf.atnn.ru

See other articles Section Application of microcircuits.

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