Hourly alarm in hours. Encyclopedia of radio electronics and electrical engineering

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

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Many radio amateurs are engaged in the development of home-made electronic clocks. Most often, K176IE18 (K176IE12) and K176IE13 microcircuits are used to make watches. But in watches on these microcircuits, there is almost always no sound signaling the end of each hour. You can enter it by making a simple device, which is described in this article.

A schematic diagram of a device that provides hourly signaling of the current time is shown in the figure. It consists of a D-flip-flop DD1.1. Schmitt trigger on the elements DD2.1, DD2.2 and the control unit of the piezoelectric BQ1 on the element DD2.3. The signaling device works as follows. With each change of readings in the discharge of the units of the clock, the logic level in the least significant bit of the binary code at pin 13 of the K176IE13 chip changes its state to the opposite. The change of state at this pin controls the D-flip-flop DD1.1. To this end, its input D (pin 5) is connected to pin 13 of the K176IE13 chip. To write to the trigger the logic levels present at this pin, pulses from pin 3 of the K1.1IE1 chip are fed to input C (pin 176) of the DD18 element. controlling the discharge of hours units.

Elements R1C1 provide a small delay of pulses at input C. At the moment of each change of readings in the discharge of units of hours, a positive voltage drop that occurs at any of the outputs of the D-flip-flop. using a circuit consisting of capacitors C2. C3 and diodes VD1. VD2. forms a voltage pulse on the left (according to the scheme) output of the resistor R4, the duration of which is determined by the values ​​of the elements C2, C3 and R4. This pulse goes to pin 9 of the K176IE18 chip and starts the alarm clock generator, the signal of which from pin 7 of the K176IE18 chip goes to pin 9 of the DD2.3 element. And, since the second input of this element (pin 8) will simultaneously receive a positive pulse from the Schmitt trigger DD2.2, the BQ1 piezoelectric emitter will emit a sound signal, the duration of which will be equal to the duration of the control pulse, i.e. will be about 0.5 s. Then, a low logic level will appear at the output of the Schmitt trigger DD2.2 (pin 4) and the sound of the emitter BQ1 will stop despite bursts of pulses from the alarm clock generator of the K176IE18 chip. arriving at pin 9 of element DD2.3 for another 1 min.

Author: I.Potachin, Fokino, Bryansk region

Addition. In the article "Hourly signaling in hours" (see "Radio", 2000. No. 3, p. 31), a simple hourly signaling device was described, designed for industrial or home-made electronic watches on K176 series microcircuits. At the same time, however, the operation of the watch in alarm mode was excluded. To save this mode, it is enough to replace the K561LA7 chip with the K561KTZ chip.

A schematic diagram of the modified device is shown in fig. 1. On the trigger DD1.1, the previously described device for generating pulses for controlling the hourly signaling unit is assembled. Its functions are performed by the key on the element DD2.1. The key connected in parallel to it on the D02.2 element controls the alarm signal, which can be turned on or off by the SA1 switch.

When the alarm clock is off (open contacts SA1), the control pulse generated by the trigger DD1.1, at the end of each hour, through the VD4 diode, enters pin 9 of the K176IE18 chip and starts its generator. At this moment, the key DD2.1 is turned on and the signal of the microcircuit generator is supplied to the piezoelectric BQ0,5 for 1 s. When the alarm clock is on (closed contacts SA1), the hourly alarm device will continue to function, but both keys D02.1 and DD2.2 will participate in parallel in its operation.

When the current time shown by the clock coincides with the set alarm time, alarm-triggering pulses will appear at pin 7 of the K176IE13 chip, which, through the decoupling diode VD1, will go to pin 9 of the K176IE18 chip and turn on its generator. The high-level signal generated from the trigger pulses through SA1 will turn on the DD2.2 key and from its output it will go to the BQ1 piezo emitter, an intermittent alarm will sound. It will sound for 1 minute. The desired signal volume is set by a variable resistor R7.

In the described device, you can not install the switch SA1, if you complicate it somewhat. In the clock, to indicate the alarm setting time, pulses are fed to pin 11 of the K.176IE13 chip from pin 1 of the K176IE18 chip (Fig. 2). With a short press on the clock button SB1, these pulses through the decoupling diode VD5 will go to the pin. 1 trigger DDI .2 and change its state. At a high logic level at pin 13 of the DDI.2 trigger, the DD2.3 key replaced the SA1 switch (see Fig. 1). will work and allow the alarm to work. If, by pressing the SB 1 button, the trigger DD1.2 is switched to a logic low state at pin 13, the key will close and the alarm clock will stop. The voltage level fluctuations at this (or inverse) trigger output can be used to indicate the alarm is on using a separate LED or to light the decimal point on the clock indicator (which is more convenient).

Thus, in this case, to control the operation of the alarm clock, it will not be necessary to introduce an additional switch, and all its functions will be performed by pressing the output button on the indicator of the indication of the alarm setting time.

See other articles Section Clocks, timers, relays, load switches.

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