SECOND COUNTS… “MOUSE” | MODEL CONSTRUCTION

Currently available a variety of models of wall elektromekhanicheski quartz watches with stepper motor. They are, as a rule, uses unpackaged integrated circuit — the oscillator/divider with an external quartz resonator coated with black compound. And had to happen that this e-node has failed in the clock, served me faithfully for years.

The required chips were unable to find them (and it’d be hard, open frame, solder in the old PCB). Had to collect the analogue of the discrete components (Fig. 1). In particular, a master oscillator to perform on the basis of CMOS inverter DD1.1, covered by a feedback.

Fig. 1. The schematic for the replacement frame MC (generator-frequency divider) in the wall of the electron-mechanical watch homemade build using discrete components, using a crystal from a broken computer “mouse”.

I applied the quartz BQ1 resonator has a frequency of 32768 Hz. Through the buffer element DD1.2 the reference signal arrives at the clock input of the counter DD2 К561ИЕ16 with division ratio of 2:14 = 16384. So its output is “2:13” will have a “welcome Doherty”. This signal is supplied further to the two series-connected frequency divider (each division ratio equal to two) based on triggers DD3.1 and DD3.2. Well, the result will be the outputs to be direct and the inverse signal with a frequency of 0.5 Hz (in other words — one drop per second).

To rotate the rotor of the stepper motor that causes the seconds hand to one position, you must submit to the coil first pulse of one polarity and then the other. It then will flow there “correct” current: first, from the beginning to the end, and later — from the end to the beginning of the winding.

With the implementation of the desired algorithm copes cascade on transistors VT1 — VT4. Direct and inverse signals are sent to the database named semiconductor triode output trigger DD3.2 through current limiting resistors R3, R4.

Let a certain point on the direct output of the trigger DD3.2 there is a high level, and the inverse is low. While being open VT1 and VT2 transistors and the current flows from the left (under the scheme) to the right end of the winding L1 of the stepper motor.

The next moment, the true output is held low, the inverse — high; open the transistor VT4, VT3 and a current flows from the right (under the scheme) to the left end of the winding. The direction of the magnetic flux in the magnetic circuit of the motor is reversed and the gradient, interacting with the magnetic field of the permanent magnet of the rotor, moves past one position. The process is repeated periodically. Resistor R3 limits the current through the motor windings, reducing the electromotive force of self-induction.

To ensure the IED power supply is the AC adapter. It can also be manufactured in any home workshop, the benefit of a circuit diagram of the adapter of the particular complexity does not differ (Fig. 2). It uses a step-down transformer with a voltage in the secondary winding 9 (“vyhodnoj” mnogoplanovo from any old radio), integrated stabilizer КР142ЕН5А, circuit breaker Yes, three capacitors, two of which — bolsaescola, electrolytic.

Fig. 2. A circuit diagram of a network adapter for hours.

Of course, can be adapted to any other power source capable of providing at the output 5 to 15 VDC. Note, however, that at increased supply voltage increases the self-induction EMF induced in the coil of the stepper motor. So, in order to avoid any complications will have to connect parallel to the load Dohnanyi semiconductor Zener КС162А limiting emissions.

The device used in integrated circuits series 564 (DD1, DD3), which can be replaced К561-m (however, this will increase the dimensions of the PCB), though as DD2 is only recommended series К561, and DA1 — КР142. КТ3102 transistors (VT1, VT4), КТ3107 (VT2, VT3) with any alphabetic index at the end of the name can be, if necessary, to replace, respectively, KT315 and KT361, and the bridge rectifier КЦ405А (VD1) is at a similar or even more powerful diode Assembly.

Capacitors, it is desirable to choose of the most common KM-5 (C1), KM-6 (C3 in Fig. 1 and C2 in Fig. 2), K50-35 (C1, C3 in Fig. 2) and resistors — from as available S2-22-0125 or their analogues.

A more stringent approach to the selection of the quartz resonator which must be tuned to the frequency of 32,768 Hz. Such used, in particular, push the manipulators of “mouse”.

The clock accuracy is determined by the precision setting of the frequency of the oscillator. Alignment here is set up by the capacitor C2. This procedure should be performed if possible, using elektronischen frequency.

The installation is carried out on a printed circuit Board from a two-sided glass epoxy or phenolic paper sizes 60x40x1,5 mm (Fig. 3).

Fig. 3. A printed circuit Board, a homemade device.

V. VASILENKO, Sverdlovsk, Luhansk region, Ukraine

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