Electronic clock circuits with indicators. Electronic watches - Clocks - Designs for home and garden

The schematic diagram of the clock is shown in Fig. It contains three high-level integrated circuits of the K176 series, two transistors and 36 other discrete elements. Indicator - flat multi-digit, cathode-lumnescent, with dynamic indication IVL1 - 7/5. It has four 21mm high numerals and two vertical dividing dots.

The generator of second and minute pulses is made on a microcircuit - IC1 K176IE18. In addition, this chip creates pulses with a repetition rate of 1024 Hz (pin 11), used to operate the signaling device. To create an intermittent signal, pulses with a repetition rate of 2 Hz are used (pin 6). A frequency of 1 Hz (pin 4) creates the effect of “blinking” the dividing dots. Pulses with a repetition rate of 128 Hz, phase-shifted relative to each other by 4 ms (pins 1, 2, 3, 15) are fed to the grids of four indicator digits, ensuring their sequential lighting. Switching of the corresponding minute and hour counters is carried out at a frequency of 1024 Hz (pin 11). Each pulse supplied to the indicator grids is equal in duration to two periods of frequency 1024 Hz, i.e. the signal supplied to the grid from the counters will be turned on and off twice. This selection of the frequency of common-mode pulses provides two effects: dynamic indication and pulsed operation of the decoder and indicator.
The integrated circuit IC2 K176IE13 contains minute and hour counters of the main clock, minute and hour counters for setting the time of the alarm device, as well as switches for switching the inputs and outputs of these counters. The outputs of the counters are connected through a switch to a binary code decoder into a seven-element indicator code. This decoder is made on the IMSZ K176IDZ microcircuit. The decoder outputs are connected to the corresponding segments of all four digits in parallel. When the S2 “Call” button is pressed, the indicator is connected to the hour counters (to identify this mode, the dot blinks at a frequency of 1 Hz). By pressing the S6 “Correction” button, the hour counters (chip K176IE13) and the dividers of the minute pulse sequence generator (chip K176IE18) are set to zero. After releasing the S6 button, the watch will work as usual. Then, by pressing the S3 “Min” and S4 “Hour” buttons, the minutes and hours of the current time are set. In this mode, a sound signal can be turned on. When the S2 “Call” button is pressed, the counters of the signaling device are connected to the decoder and indicator. In this mode, four digits are also displayed, but the flashing dots go out. By pressing the S5 “Bud” button and holding it, press the S3 “Min” and S4 “Hour” buttons in sequence, set the required response time of the alarm device, observing the indicator readings. The clock circuit allows you to set a reduced brightness of the indicators using the S1 “Brightness” button. However, it should be remembered that when the brightness is reduced (button S1 is pressed), turning on the sound signal, as well as setting the clock time and alarm device, is impossible.
The power supply unit BP6 - 1 - 1 contains a network transformer T, which creates a voltage of 5 V (with a midpoint) to power the filament of the indicator cathode and a voltage of 30 V to power the remaining circuits of the indicator and microcircuits. A voltage of 30 V is rectified by a ring circuit on four diodes (VD10 - VD13), and then using a stabilizer on the zener diode VD16 relative to the housing, a voltage of +9 V is created to power the microcircuits, and with the help of a stabilizer on the zener diodes VD14, VD15 and transistor VT2 - voltage + 25 V (relative to the cathode) to power the grids and anodes of the indicators. The power consumed by the clock is no more than 5 W. A backup power connection is provided to save the clock time when the network is turned off. Any 6...9V battery can be used.

Literature MRB1089

For those who have at least a little knowledge of microcontrollers and also want to create a simple and useful device for the home, there is nothing better than an assembly with LED indicators. Such a thing can decorate your room, or it can be used as a unique handmade gift, from which it will acquire additional value. The circuit works like a clock and like a thermometer - modes are switched with a button or automatically.

Electrical diagram of a homemade clock with a thermometer

Microcontroller PIC18F25K22 takes care of all data processing and timing, and a share ULN2803A All that remains is to coordinate its outputs with the LED indicator. Small chip DS1302 works as a timer of precise second signals, its frequency is stabilized by a standard quartz resonator of 32768 Hz. This complicates the design somewhat, but you won’t have to constantly adjust and adjust the time, which will inevitably be delayed or rushed if you get by with a random untuned quartz resonator of a few MHz. A watch like this is more of a simple toy than a high-quality, accurate timepiece.

If necessary, temperature sensors can be located far from the main unit - they are connected to it with a three-wire cable. In our case, one temperature sensor is installed in the block, and the other is located outside, on a cable about 50 cm long. When we tried a 5 m cable, it also functioned perfectly.

The clock display is made of four large LED digital indicators. They were originally common cathode, but changed to common anode in the final version. You can install any others, then simply select current-limiting resistors R1-R7 based on the required brightness. You could place it on a common board with the electronic part of the watch, but this is much more universal - suddenly you want to put a very large LED indicator so that they can be seen from a long distance. An example of such a design of a street clock is here.

The electronics themselves start from 5 V, but for the LEDs to glow brightly it is necessary to use 12 V. From the network, power is supplied through a step-down transformer adapter to the stabilizer 7805 , which produces a voltage of strictly 5 V. Pay attention to the small green cylindrical battery - it serves as a backup power source in case the 220 V network is lost. It is not necessary to take it at 5 V - a lithium-ion or Ni-MH battery for 3.6 is enough Volt.

For the case, you can use various materials - wood, plastic, metal, or integrate the entire structure of a homemade watch into a ready-made industrial one, for example, from a multimeter, tuner, radio receiver, and so on. We made it from plexiglass because it is easy to process and allows you to see the insides so that everyone can see - this watch was assembled with your own hands. And, most importantly, it was available :)

Here you can find all the necessary details of the proposed homemade digital clock design, including the circuit diagram, PCB layout, PIC firmware and

Not long ago I was digging through a box of old components. I was looking for something else, but stopped when I came across several gas discharge indicators. One day (a long, long time ago) I got them out of an old calculator.

I remember... Thirty years ago, six indicators were a small treasure. Anyone who could then make a clock using TTL logic with such indicators was considered a sophisticated expert in his field.

The glow of the gas-discharge indicators seemed warmer. After a few minutes I was wondering if these old lamps would work and wanted to do something with them. Now it is very easy to make such a watch. All you need is a microcontroller...

Since at the same time I was interested in programming microcontrollers in high-level languages, I decided to play a little. I tried to construct a simple clock using digital gas discharge indicators.

Purpose of design

I decided that the clock should have six digits, and the time should be set with a minimum number of buttons. Additionally, I wanted to try to use several of the most common families of microcontrollers from different manufacturers. I intended to write the program in C.

Gas discharge indicators require high voltage to operate. But I didn’t want to deal with dangerous mains voltage. The watch was supposed to be powered by a harmless 12 V voltage.

Since my main goal was the game, you will not find any description of the mechanical design or body drawings here. If you wish, you can change the watch yourself in accordance with your tastes and experience.

Here's what I got:

• Time display: HH MM SS
• Alarm indication: HH MM --
• Time display mode: 24 hours
• Accuracy ±1 second per day (depending on quartz crystal)
• Supply voltage: 12 V
• Current consumption: 100 mA

Clock diagram

For a device with a six-digit digital display, multiplex mode was a natural solution.

The purpose of most elements of the block diagram (Figure 1) is clear without comment. To a certain extent, the non-standard task was to create a converter of TTL levels into high-voltage indicator control signals. The anode drivers are made using high-voltage NPN and PNP transistors. The diagram is borrowed from Stefan Kneller (http://www.stefankneller.de).

The 74141 TTL chip contains a BCD decoder and a high-voltage driver for each digit. It may be difficult to order one chip. (Although I don't know if anyone makes them anymore). But if you find gas-discharge indicators, 74141 may be somewhere nearby :-). At the time of TTL logic, there was practically no alternative to the 74141 chip. So try to find one somewhere.

The indicators require a voltage of about 170 V. It makes no sense to develop a special circuit for a voltage converter, since there are a huge number of boost converter chips. I chose the inexpensive and widely available IC34063. The converter circuit is almost completely copied from the MC34063 data sheet. A T13 power switch has just been added to it. The internal switch is not suitable for such high voltage. I used a choke as inductance for the converter. It is shown in Figure 2; its diameter is 8 mm and its length is 10 mm.

The efficiency of the converter is quite good, and the output voltage is relatively safe. With a load current of 5 mA, the output voltage drops to 60 V. R32 acts as a current-sensing resistor.

To power the logic, linear regulator U4 is used. There is space on the circuit and board for a backup battery. (3.6 V - NiMH or NiCd). D7 and D8 are Schottky diodes, and resistor R37 is designed to limit the charging current according to the characteristics of the battery. If you are building watches just for fun, you won't need the battery, D7, D8 and R37.

The final circuit is shown in Figure 3.

Figure 3.

The time setting buttons are connected via diodes. The state of the buttons is checked by setting a logical “1” at the corresponding output. As a bonus feature, a piezo emitter is connected to the output of the microcontroller. To shut up that nasty squeak, use a small switch. A hammer would be quite suitable for this, but this is a last resort :-).

A list of circuit components, a PCB drawing and a layout diagram can be found in the "Downloads" section.

CPU

Almost any microcontroller with a sufficient number of pins, the minimum required number of which is indicated in Table 1, can control this simple device.

Table 1.

Function conclusions Nutrition 2 Quartz resonator 2 Anode management 6 Driver 74141 4 Button input 1 Piezo emitter 1 Total 16

Each manufacturer develops its own families and types of microcontrollers. The location of the pins is individual for each type. I tried to design a universal board for several types of microcontrollers. The board has a 20-pin socket. With a few jumper wires you can adapt it to different microcontrollers.

The microcontrollers tested in this circuit are listed below. You can experiment with other types. The advantage of the scheme is the ability to use different processors. Radio amateurs, as a rule, use one family of microcontrollers and have the corresponding programmer and software tools. There may be problems with microcontrollers from other manufacturers, so I gave you the opportunity to choose a processor from your favorite family.

All the specifics of switching on various microcontrollers are reflected in Tables 2...5 and Figures 4...7.

Table 2.

Freescale Type MC68HC908QY1 Quartz resonator 12 MHz Capacitors C1, C2 22 pF Program freescale.zip (see "Downloads" section) Settings —

Note: A 10 MΩ resistor is connected in parallel with the quartz resonator.

Table 3.

Microchip Type PIC16F628A Quartz resonator 32.768 kHz Capacitors C1, C2 22 pF Program pic628.zip (see "Downloads" section) Settings Int. 4 MHz generator - I/O RA6, MCLR OFF, WDT OFF, LVP OFF, BROUT OFF, CP OFF, PWRUP OFF

Note: The microcircuit must be rotated 180° in the socket.

Table 4.

Atmel Type ATtiny2313 Quartz resonator 12 MHz Capacitors C1, C2 15 pF Program attiny.zip (see "Downloads" section) Settings Sq. 8 MHz oscillator, RESET ON

Note: Add SMD components R and C to the RESET pin (10 kΩ and 100 nF).

Table 5.

Atmel Type AT89C2051 Quartz resonator 12 MHz Capacitors C1, C2 22 pF Program at2051.zip (see "Downloads" section) Settings --

Note: Add SMD components R and C to the RESET pin (10 kΩ and 100 nF); connect the pins marked with asterisks to the +Ub power bus via 3.3 kOhm SMD resistors.

When you compare the codes for different microcontrollers, you will see that they are very similar. There are differences in access to ports and definition of interrupt functions, as well as in what depends on the hardware components.

The source code consists of two sections. Function main() configures ports and starts a timer that generates interrupt signals. After this, the program scans the pressed buttons and sets the appropriate time and alarm values. There, in the main loop, the current time is compared with the alarm clock and the piezo emitter is turned on.

The second part is a subroutine for handling timer interrupts. A subroutine that is called every millisecond (depending on the timer's capabilities) increments the time variables and controls the display digits. In addition, the status of the buttons is checked.

Running the circuit

When installing components and setting up, start with the power source. Solder the U4 regulator and surrounding components. Check for 5 V voltage for U2 and 4.6 V for U1. The next step is to assemble the high voltage converter. Use trimming resistor R36 to set the voltage to 170 V. If the adjustment range is not enough, slightly change the resistance of resistor R33. Now install the U2 chip, transistors and resistors of the anode and digital driver circuit. Connect the U2 inputs to the GND bus and connect one of the resistors R25 - R30 in series to the +Ub power bus. The indicator numbers should light up in the corresponding positions. At the last stage of checking the circuit, connect pin 19 of the U1 microcircuit to ground - the piezo emitter should beep.

You will find the source codes and compiled programs in the corresponding ZIP file in the “Downloads” section. After flashing the program into the microcontroller, carefully check each pin in position U1 and install the necessary wire and solder jumpers. Refer to the microcontroller images above. If the microcontroller is programmed and connected correctly, its generator should start working. You can set the time and alarm. Attention! There is space on the board for one more button - this is a spare button for future expansions :-).

Check generator frequency accuracy. If it is not within the expected range, slightly change the values ​​of capacitors C1 and C2. (Solder small capacitors in parallel or replace them with others). The accuracy of the watch should improve.

Conclusion

Small 8-bit processors are quite suitable for high-level languages. C was not originally intended for small microcontrollers, but for simple applications you can use it just fine. Assembly language is better suited for complex tasks that require critical times or maximum CPU load. For most radio amateurs, both free and shareware limited versions of the C compiler are suitable.

C programming is the same for all microcontrollers. You must know the hardware functions (registers and peripherals) of the selected type of microcontroller. Be careful with bit operations - the C language is not suitable for manipulating individual bits, as can be seen in the example of the original when for ATtiny.

Are you done? Then tune in to contemplate the vacuum tubes and watch...

...the old days are back... :-)

Editor's note

A complete analogue of the SN74141 is the K155ID1 microcircuit, produced by the Minsk Integral software.
The microcircuit can be easily found on the Internet.

Currently, the electronics industry produces a significant number of table and car clocks, varying in circuits, indicators used and design. Table 1 gives some idea of ​​the mass-produced watches. 2. Let's consider the features of serial solutions of some of these watches.

“Electronics 2-05” is a table clock showing hours and minutes with the ability to issue a sound signal. The schematic diagram of the clock is shown in Fig. 47. It contains 11 K176 series microcircuits and four K161 series microcircuits, one transistor and 38 other discrete elements. The indicator uses four IV-12 lamps and one IV-1 lamp (for the flashing dash).

table 2

Designation	Indicator type	Power supply	Functions performed
"Electronics 3/1" (desktop)	Izhkts-6/7	Standalone 6 V	Hours, minutes, seconds with backlight
"Electronics 16/7" (desktop)	IZhKTs-6/7	Standalone 3V	Hours, minutes, day of week, def. dividing the day of the month
"Electronics 6/11" (desktop)	IVL1-7/5	Network 220 V	Hours, minutes, with the issuance of an audible signal at a given time (alarm function). Can function as a stopwatch or timer
"Electronics 6/14" (desktop)	IV-6	Network 220 V	Hours, minutes with a sound signal at a given time (alarm function)
"Electronics 2-05	IV-12	Network 220 V	Hours, minutes with a sound signal at a given time (alarm function). Possibility to change the brightness of the indicator
"Electronics 2-06" (desktop)	IVL 1-7/5	Network 220 V	Hours, minutes with a sound signal at a given time (alarm function). Possibility of changing the brightness of the indicator
"Electronics 2-07" (desktop with built-in radio)	IVL 1-7/5	Network 220 V	Hours, minutes with a sound signal at a given time (alarm function). Turn on the radio at a specified time. Reception of radio programs in the VHF range on five fixed frequencies in continuous or programmable operating mode
"Electronics-12" (automotive)	ALS-324B	12 V on-board network	Hours, minutes. Ability to change brightness and turn off indicator

The clock circuit is made on microcircuits IMS4, IMS8, IMS11 and differs from the usual scheme in two features. The first is that the outputs of the decoder chips K176IEZ, K176IE4 are connected to indicator segments through transistor switches (chips K161KN1). This allows you to supply digital indicators with a voltage of 25 V, which ensures a higher brightness of their glow. Each K161KN1 microcircuit has seven keys. The watch uses four such microcircuits: 23 keys switch decoder signals, one key - a signal with a frequency of 1 Hz (flashing dash), one - a tens of hours indicator grid (to turn off when the indication is digit 0), one - to amplify the 1024 Hz signal supplied to the dynamic head of the alarm clock, one - to isolate the signal with a repetition rate of 1 minute, supplied to the control terminals, one key - reserve.

The second feature is the system for initially setting the clock time. To set the time, a signaling device circuit is used. Switches 1 S2 - S5 are placed in positions corresponding to the required time, for example - 1200. When the exact time is signaled, the button is pressed S7"Record". Wherein. all counters, including the signaling device, are set to the zero state using 2I-NOT logic elements IMS7.1, IMS7.2. After this, instead of a signal with a frequency of 1/60 Hz, a signal with a frequency of 32768 Hz is supplied to the clock circuit. Even when pressing the button briefly S7 counters; manage to “write down” the required number, after which the matching circuit of the signal device (diodes VD7 - VD10 and a 2OR-NOT logic gate. IMS5.2), which stops the flow of a signal with a frequency of 32768 Hz through the 2I-NOT logic element IMS6.4. The clock counters and the signaling device will subsequently receive a signal with a frequency of 1/60 Hz (through the 2OR-NOT element IMS6.1).

When the power is turned on, all clock and alarm counters are set to zero using a transistor circuit VT1. When voltage appears on the collector of the transistor and there is no voltage on the capacitor NW the transistor will turn off. At the output of the 2I-NOT logic element IMS7.2 a positive potential will appear, which will set the dividers of the K176IE12 microcircuit to 0. Simultaneously through the 2I-NOT element IMS7.1 The clock and alarm counters will be set to 0. When charging the capacitor SZ through a resistor R7 the transistor will open, at both inputs of the element - IMS7.2 a positive potential will appear, and the output signal will be logical 0. The counters will start working.

The signaling device consists of hour and minute counters, time setting switches 52- - S5, matching circuits and audible alarms. The operation of all elements of the alarm device of this clock is discussed in § 7.

The power supply consists of a mains transformer T, providing an alternating voltage of 1.2 V to power the filament circuits of the cathodes of the lamps, as well as a voltage of 30 V to power the remaining elements of the clock. After diode rectification VD3 The result is a constant voltage of 25 V, supplied to the cathodes of the lamps. Using the “Brightness” switch, you can change the brightness of the indicators.

From +25 V voltage using a resistor R4 and zener diode VD5 a voltage of +9 V is created to power the microcircuits. To ensure the operation of the main clock circuit in the event of a power failure, a G battery with a voltage of 6 - 9 V is included. The power consumed by the clock is about 6 W.

“Electronics 2-06” is a table-type clock with an alarm device.

Rice. 48. Schematic diagram of the watch “Electronics 2-06”

The schematic diagram of the clock is shown in Fig. 48. It contains three high-level integration microcircuits of the K176 series, two transistors and 36 other discrete elements. Indicator - - flat multi-digit, cathode-mnescent, with dynamic indication IV L1-7/5. It has four 21mm high numerals and two vertical dividing dots.

The generator of second and minute pulses is made on a microcircuit -IMS1 K176IE18. In addition, this chip creates pulses with a repetition rate of 1024 Hz (pin 11), used to operate the signaling device. To create an intermittent signal, pulses with a repetition rate of 2 Hz are used (output 6). Frequency 1 Hz (output 4) creates the effect of “blinking” dividing dots.

Pulses with a repetition rate of 128 Hz, shifted relative to each other in phase by 4 ms (terminals 1, 2, 3, 15) are fed to the grids of the four digits of the indicator, ensuring their sequential lighting. Switching of the corresponding minute and hour counters is carried out at a frequency of 1024 Hz (output 11). Each pulse supplied to the indicator grids is equal in duration to two periods of frequency 1024 Hz, i.e. the signal supplied to the grid from the counters will be turned on and off twice. This selection of the frequency of common-mode pulses provides two effects: dynamic indication and pulsed operation of the decoder and indicator. The principle of dynamic indication is discussed in more detail in § 1.

Integrated circuit IMS2 K176IE13 contains minute counters and. hours of the main clock, minute and hour counters for setting the time of the alarm device, as well as switches for switching the inputs and outputs of these counters. The outputs of the counters are connected through a switch to a binary code decoder into a seven-element indicator code. This decoder is made on a microcircuit IMSZ K176IDZ. The decoder outputs are connected to the corresponding segments of all four digits in parallel.

When the button is pressed S2 The “bell” indicator is connected to the hour counters (to identify this mode, the dot blinks at a frequency of 1 Hz). By pressing the button S6“Corr.”, the hour counters (chip K176IE13) and the dividers of the minute pulse sequence generator (chip K176IE18) are set to zero. After releasing the button S6 the clock will work as usual. Then by pressing the buttons S3"Min" and S4“Hour” sets the minutes and hours of the current time. In this mode, a sound signal can be turned on.

When the button is pressed S2“Call” the counters of the signaling device are connected to the decoder and indicator. In this mode, four digits are also displayed, but the flashing dots go out. By pressing the button S5“Bud” and holding it, press sequentially on the buttons S3 “Min” and S4“Hour”, set the required response time of the alarm device by observing the indicator readings.

The clock circuit allows you to set the reduced brightness of the indicators using the button S1"Brightness". However, it should be remembered that with reduced brightness (button S1 pressed), activation of the sound signal, as well as setting the clock time and alarm device are not possible.

The power supply unit BP6-1-1 contains a network transformer T, creating a voltage of 5 V (with a midpoint) to power the filament of the indicator cathode and a voltage of 30 V to power the remaining indicator circuits and microcircuits. The 30 V voltage is rectified by a ring circuit using four diodes (UD 10- VD13), and then using a stabilizer on a zener diode VD16 relative to the housing, a voltage of +9 V is created to power the microcircuits, and with the help of a stabilizer on zener diodes VD14, VD15 and transistor VT2- voltage +25 V (relative to the cathode) to power the grids and anodes of the indicators. The power consumed by the clock is no more than 5 W. A backup power connection is provided to save the clock time when the network is turned off. Any 6 V battery can be used.

Car watch "Electronics-12". The watch allows you to determine the time with an accuracy of 1 minute, change the brightness of the indicators, and also turn off the indication during long-term parking. The clock circuit is made of eight microcircuits and 29 transistors (Fig. 49).

Rice. 49. Schematic diagram of the “Electronics-12” car clock

The second pulse generator is made on an integrated circuit - IMS1 and quartz at a frequency of 32768 Hz. Pulses with a repetition rate of 1 Hz are used to receive minute pulses, ensure the operation of the “blinking” dot, and also to set the time.

Microcircuits are used to obtain minute pulses IMS2„ IMSZ. Next, using microcircuits IMS4-IMS7 minutes and hours are counted. The outputs of the decoder of these microcircuits through transistors VT1 - VT25 fed to the LEDs of digital indicators. Transistors are needed to match the low-current outputs of decoder chips K176IEZ. K176IE4 with LEDs that require a current of about 20 mA to obtain normal brightness.

The minutes are set by sending second pulses to the input 4 microcircuits IMS4 through the contacts of the S3 button, setting the clock - by applying second pulses to the input 4 microcircuits IMS6 via button S2. Setting the state of 0 chip dividers and counters IMS1 - IMS5 carried out using a button S4. In this case, the moving contact of the button is connected to the body, which corresponds to the input 8 logical element-ZI-NOT (microcircuit IMS8 K176LA9) logical 0. Since the other two inputs 1 and 2 through a resistor R62 When the positive voltage of the power source is applied, the output 9 In the logical element, a positive differential will appear, which will set the dividers and counters to 0. The rest of the time, the output of the logical element will have a voltage close to 0 V, which will ensure normal operation of the microcircuits.

To set the clock counters to state 0 when the number 24 is reached, two other logic circuits of the ZI-NOT microcircuit are used IMS8. Conclusions 3 chips IMS6 And IMS7 supplied to the inputs 3 And 5 logical element. To the third entrance 4 Pulses are constantly received with a repetition rate of 1 Hz. Since the logical element inverts the input signals, the second logical element ZI-NOT is used to obtain a positive control pulse. For one of his entrances (11) impulses are sent from the output & the first logical element, and the other two (12 And 13) - positive voltage through a resistor R61. Therefore, at the exit 9 second pulses will appear only if there are 3 microcircuits at the outputs IMS6, IMST there will be a positive voltage, which corresponds to the number 24.

The LEDs, and through them the transistor switches, are powered: through a transistor VT29. There is a switch included in its base S5"Brightness". If the moving contact 2 switch is closed with contact 1, then a voltage of +8.5 V is applied to the base of the transistor, the transistor will be open, and at its emitter in relation to the body there will be a voltage of +7.9 V, which will ensure maximum brightness of the LED. To reduce the brightness (which increases the service life of the indicators), the switch is placed in a different position. To the base of the transistor VT29 through a resistor R65 a voltage of about 7 V is supplied, which will lead to a decrease in the output voltage to 6.5 V and a decrease in the brightness of the indicators.

To turn off the indication with the switch S1 to the emitters of the transistor" VT1 - VT27 the housing is supplied instead of the positive voltage supplied through the resistor R64. This will turn off all transistors and turn off the indicator.

The clock is powered from the car's on-board network, the voltage of which can vary from 12.6 to 14.2 V. Therefore, the microcircuits are powered through a voltage stabilizer made on a zener diode VD1 and transistor VT28. Output voltage is +8.5 V. The power consumed by the clock at maximum brightness of the indicators is about 10 W.