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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Primary clock. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Clocks, timers, relays, load switches The version of the primary clock offered to the attention of readers allows (unlike its predecessors) to connect a larger number of secondary clocks to them. But their main advantage is the possibility of synchronous adjustment of the readings of all clocks directly from the "clock station". The schematic diagram of the primary clock is shown in the figure. For simplicity, it does not show the minute pulse generator. It is made on a K176IE12 chip and a quartz resonator at a frequency of 32 Hz, connected according to a typical circuit [768, 1].
In the "Run" mode, minute pulses from the output M (pin 10) of the K176IE12 microcircuit through the SA1 switch are fed to the counting input (pin 3) of the DD1 trigger. It reduces the pulse repetition rate by half and provides a shift between the fronts of the pulses coming from its direct and inverse outputs to the counting inputs of triggers DD2.1 and DD2.2, equal to 1 min. Pulses on the output. 1 microcircuits DD1 we will conditionally call direct, and on the pin. 2 - inverse. From a direct minute pulse, a single vibrator is started on the DD2.1 element, and from an inverse one - on the DD2.2 element. Let us explain their work on the example of a single vibrator on the element DD2.1. When it is launched on the output. 1 element DD2.1 appears log. 1 and the capacitor C4 begins to charge through the resistor R3. When the voltage on it reaches the value necessary to switch the trigger DD2.1, the latter will return to the zero state. Thus, on the output. 1 element DD2.1 there will be a pulse, the duration of which depends on the values of the resistor R3 and capacitor C4. With the ratings indicated on the diagram, it is 2 s. After the trigger returns to the zero state, the capacitor C4 quickly discharges through the diode VD4 [3]. The single vibrator on the DD2.2 element works in a similar way, only from inverse minute pulses. In the "Tune" mode, pulses with a frequency of 2 Hz are fed to the counting input of the trigger DD1 with pin. 6 microcircuits K176IE12. In this mode, the capacitor C4 does not have time to charge up to the voltage required to switch the trigger DD2.1 to the zero state, because the inverse pulse will be sent to the counting input (pin 13) of the trigger DD2.2 too quickly. As a result, it switches and a log level appears on its output 15. 1. After that, due to the summation of the voltages on the capacitor C4 and on the pin. 15 element DD2.2, the voltage at the input R of the element DD2.1 increases to the voltage of the power source and it switches to the zero state. The specified voltage cannot rise above this value due to the opening protective diode VD2. Further, through the opened diode VD4, the capacitor C4 is charged to the supply voltage, but in a different polarity. Now, after the arrival of the next direct pulse, the trigger DD2.1 switches back to the single state. The trigger DD2.2 switches to the zero state according to the principle just described, but when the capacitor C3 is charged. The voltage on the plates of the capacitor C4 will change in this case to the opposite, since the output 15 of the trigger DD2.2 will have a log level. 0. Diode VD3 in the process of recharging capacitor C4 will be open. When a positive voltage appears on the upper plate of the capacitor C4 according to the scheme, the diode VD3 will close and the whole process will repeat itself. In other words, the flip-flops alternately switch to the single and zero states synchronously with the arrival at their counting inputs of the fronts of the pulses from the outputs of the trigger DD1. Pulse amplifiers are made on transistors VT2-VT7. In the "Run" mode, with zero states of triggers DD2.1 and DD2.2, transistors VT2, VT5 are closed, VT3, VT6 are open, and VT4, VT7 are closed. At the outputs of the "clock station" (Out. 1 and Out. 2), there is the same voltage of about +27 V. The current does not flow through the coils of the stepper motors of the secondary clock at this time. After arrival at the counting input of the trigger DD2.1 direct minute pulse for 2 s to its pin. 1 log level appears. 1. At the same time, transistor VT2 opens, VT3 closes and VT4 opens. On Exit. 1 "clock station" voltage appears close to zero, and on the Out. 2 - about 27 V remains. In this mode, a two-second pulse will go to the coils of the stepper motors of the secondary clock and they will move the hands of the latter by 1 minute. In order for the clock hands to move another 1 minute, it is necessary that the Exit. 2 appeared zero voltage, and on the Out. 1 - voltage +27 V. This will happen when an inverse minute pulse arrives at the counting input of the trigger DD2.2 and for 2 s at its output. 15 the log level will appear. 1. In the "Trimming" mode in the secondary clock circuit, bipolar pulses with a duration of 0,5 s follow one after the other (Out. 1 and Out. 2 of the "clock station"). When adjusting the readings of the secondary clocks, this mode is most preferable, since the clockwork will be held by the magnetic field of the stepper motor coils, preventing the occurrence of mechanical oscillatory processes and thus preventing the possibility of failures. The clock hands will move in this mode, although quickly, but synchronously with each other. In the middle position of the SA1 switch, the generator pulses are not received at the counting input of the trigger DD1, and there will be a positive voltage on it created by the resistor R1 included in the power supply circuit of the "clock station". The clock hands can also be translated by pressing the buttons SB1 and SB2 in turn. This is done both in the neutral position of the switch SA1, and in the "Run" mode. It should only be remembered that when lagging behind, the clock hands move only an even number of steps - 2, 4, 6, etc. When you need to move the hands back, it is better to stop the clock by switching the switch SA1 to the neutral position and skipping the necessary, but necessarily a multiple of two , the number of pulses. During the transition to winter time, it is better to stop the clock for 1 hour. If the hands need to be moved in one direction or another by 1, 3, 5, etc. 1 and Out. 2. It is most convenient to do this by introducing an additional switch. The described "clock station" is powered by a rechargeable battery of twenty D-0,55 cells. In the author's version, its charging is monitored by a threshold device on the K554CA3 comparator. It can be built using the recommendations contained in [4], but taking into account that in our case we are talking about a 24 V battery with a charging current of 80 mA. A 28% charge of such a battery corresponds to a voltage of 1 V. A threshold device should respond to this value. Depending on the resistance of the stepper motor coils (2,5 or 30 kOhm), it is permissible to connect from 70 to XNUMX secondary clocks to the "clock station". Literature
Author: L. Maslyaev, St. Petersburg
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