Computer mouse for quartz clocks. Scheme, description

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Computer mouse for quartz clocks. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Clocks, timers, relays, load switches

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Currently, many models of wall-mounted electromechanical quartz clocks with a stepper motor are being produced. They, as a rule, use a packageless integrated circuit - an oscillator / divider with an external quartz resonator, filled with a black compound. And it had to happen that it was this electronic unit that failed in a watch that served me faithfully for more than one year.

It was not possible to get the required microcircuit (and it would be difficult to solder it, unpackaged, into the old printed circuit board). I had to assemble an analog from discrete components (Fig. 1). In particular, the master oscillator is based on a CMOS inverter DD1.1 covered by feedback.

Rice. 1. A circuit solution for replacing a frameless MS (frequency divider generator) in a home-made electronic-mechanical wall clock assembled on discrete elements using a quartz resonator from a broken computer "mouse" (click to enlarge)

The BQ1 quartz resonator I used has a frequency of 32768 Hz. Through the buffer element DD1.2, the reference signal comes to the clock input of the counter DD2 K561IE16 with a division ratio of 2:14 = 16384. So, at its output "2:13" we will have the "desired two-hertz". This signal is then fed to two series-connected frequency dividers (each division ratio is equal to two) based on triggers DD3.1 and DD3.2. Well, as a result, there will be a direct and inverse signal with a frequency of 0,5 Hz at the outputs (in other words, one drop per second).

In order to turn the rotor of a stepper motor that leads the second hand to one position, it is necessary to first apply a pulse of one polarity to its winding, then another. It is then that the "correct" current will flow there: first from the beginning to the end, and later - from the end to the beginning of the winding.

The cascade on transistors VT1 - VT4 successfully copes with the implementation of the required algorithm. The direct and inverse signals are fed to the bases of the named semiconductor triodes from the output of the DD3.2 trigger through current-limiting resistors R3, R4.

Let at a certain moment on the direct output of the trigger DD3.2 there is a high level, and on the inverse - low. At the same time, transistors VT1 and VT2 are open - and the current flows from the left (according to the diagram) to the right end of the winding L1 of the stepper motor.

The next moment, there is a low level at the direct output, a high level at the inverse; at the same time, transistors VT4, VT3 are open - and the current flows from the right (according to 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 this difference, interacting with the magnetic field of the permanent magnet of the rotor, moves the latter by one position. The process is then repeated periodically. Resistor R3 limits the current through the motor winding, reducing the EMF of self-induction.

To provide a home-made device with power, a network adapter is used. It can also be made in the conditions of any home workshop, since the circuit diagram of such an adapter is not particularly complicated (Fig. 2). It uses a step-down transformer with a voltage on the secondary winding of 9 V (an "exit" from any old multi-tube radio is suitable), an integral stabilizer KR142EN5A, a switch and a triple of capacitors, two of which are high-capacity, electrolytic.

Rice. 2. Schematic diagram of the network adapter for watches (click to enlarge)

Of course, you can adapt to power any other source that can provide 5-15 V DC output. However, it should be borne in mind that with an increased supply voltage, the self-induction EMF induced in the stepper motor winding increases. This means that in order to avoid any complications, it will be necessary to connect a two-anode semiconductor zener diode KS162A in parallel with the load, limiting emissions.

The device uses integrated circuits of the 564 series (DD1, DD3), which can be replaced by the K561-m (however, the dimensions of the printed circuit board will increase), although it is recommended to use only the K2 series as DD561, and DA1 - KR142. Transistors KT3102 (VT1, VT4), KT3107 (VT2, VT3) with any letter index at the end of the name can, if necessary, be replaced by, respectively, KT315 and KT361, and the rectifier bridge KTs405A (VD1) - by a similar or even more powerful diode assembly .

It is advisable to choose capacitors from the widely used KM-5 (C1), KM-6 (C3 in Fig. 1 and C2 in Fig. 2), K50-35 (C1, C3 in Fig. 2), and resistors - from equally available С2-22-0125 or their analogues.

A more rigid approach is to choose a quartz resonator, which must be tuned to a frequency of 32768 Hz. It is this that is used, in particular, in the mouse button manipulators.

The error of the clock is determined by the accuracy of setting the frequency of the master oscillator. The adjustment here is carried out by a tuned capacitor C2. This procedure should be carried out, if possible, using an electronic frequency counter.

The clock is mounted on a printed circuit board made of double-sided foil textolite or getinax with dimensions of 60x40x1,5 mm (Fig. 3).

Computer mouse for quartz clocks
Rice. 3. Topology of the printed circuit board of a homemade device

Author: V.Vasilenko

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