Greetings! The review will be devoted to the IV-18 vacuum-luminescent indicator and the assembly of watches based on it. I'll tell you about each functional unit in the diagram, there will be a lot of photos, pictures, text and, of course, DIY. If interested, go to cut.
Just a little bit of poetry
I have long had the idea of assembling a watch with gas-discharge or luminescent indicators. Agree - it looks vintage, warm and lamp-like. Such a watch, for example, in a wooden case, can take its rightful place in the interior or on the table of a radio amateur. It somehow didn’t work out to implement my idea. At first I wanted to assemble it on the IV-12. These lamps were found in a pile of “junk” at home.
(Picture for example from the Internet). 
Then to IN-18. This is one of the largest indicator lamps, but after learning the price of one piece, I abandoned this idea. (Picture for example from the Internet). 
Then I wanted to repeat the scheme on IN-14. (Picture for example from the Internet). 
I have already routed the printed circuit board, but there was a hitch due to the lamps. It was not possible to find them in Norilsk. Then I found a set of 6 on ebay. While I was thinking about it, my enthusiasm waned and other projects appeared. The idea was again not implemented.
On one of the thematic sites for radio amateurs, I saw a watch like this. 
I found information, it turned out to be Ice Tube Clock from Adafruit. I really liked them, but the price for the DIY kit is $85, not including shipping. I immediately came to the decision - I will collect it myself! The indicator in such watches is IV-18. I couldn’t buy the same one in Russian online stores, either there was no delivery to Norilsk, or the sale was only in bulk. In general, in a fit of enthusiasm I ordered it on ebay. The seller turned out to be from Nizhny Tagil (delivers all over the world). After payment, the seller returned the cost of international shipping $5. After 3 weeks the parcel was in my hands. Just in case, I ordered 2 pieces, as I was worried that they might break on the road.
Package
The packaging was a regular envelope with bubble wrap; the indicators were in plastic tubes with additional wrapping inside. This form of packaging turned out to be quite reliable. 
Appearance
Purpose and device
The digital multi-digit vacuum luminescent indicator (VLI) is designed to display information in the form of numbers from 0 to 9 and a decimal place in each of the 8 digital digits, and auxiliary information on one service digit.
VLI is a directly heated electric vacuum triode with many phosphor-coated anodes. The lamp parameters are selected so that it can operate at low anode voltages - from 27 to 50 V.
The cathode is a directly heated tungsten cathode with the addition of 2% thorium to facilitate emission at a relatively low temperature.
The indicator contains two parallel-connected filaments with a diameter smaller than a human hair. Small flat springs are used to tension them. The filament voltage ranges from 4.3 to 5.5 V.
VLI grids are flat. The number of grids is equal to the number of indicator familiarities. The purpose of the grids is twofold: firstly, they reduce the voltage sufficient for the indicator to glow brightly, and secondly, they provide the ability to switch bits during dynamic display.
The anodes are coated with a phosphor with a low excitation energy of only a few electron volts. It is this fact that allows the lamp to operate at a low anode voltage.
Specifications
Light color: Green
The nominal brightness of the indicator for one digital digit is 900 cd/m2, the service digit is 200 cd/m2.
Filament voltage: 4.3–5.5 V
Filament current: 85±10mA
Anode-segment pulse voltage: 50 V
The highest voltage of the anode segments: 70 V
Highest anode segment current: 1.3 mA
Pulse total current of anode segments IV-18: 40 mA
Grid voltage pulse: 50 V
Highest grid pulse voltage: 70 V
Minimum operating time: 10,000 h
Indicator brightness, changing during minimum operating time, not less than: 100 cd/m2
dimensions
Pinout IV-18 (type-2)
1– Cathode, a conductive layer of the inner surface of the cylinder;
2– dp1...dp8 – anode segments from the 1st to the 8th digit;
3 – d1...d8 – anode segments from the 1st to the 8th digit;
4 – c1...c8 – anode segments from the 1st to the 8th digit;
5 – e1...e8 – anode segments from the 1st to the 8th digit;
6 – Do not connect (free);
7 – Do not connect (free);
8– Do not connect (free);
9 – g1...g8 – anode segments from the 1st to the 8th digit;
10 – b1...b8 – anode segments from the 1st to the 8th digit;
11 – f1...f8 – anode segments from the 1st to the 8th digit;
12 – a1...a8 – anode segments from the 1st to the 8th digit;
13 – Cathode;
14 – 9th category grid;
15 – 1st category grid;
16 – 3rd category grid;
17 – 5th category grid;
18 – 8th category grid;
19 – 7th category grid;
20 – 6th category grid;
21 – 4th category grid;
22 – 2nd category grid.
Information about pin assignments is valid only for the indicator type-2. There is also type-1, but how do you know which “type” of indicator you will have?! It's simple! Based on the description, pins 6, 7, 8 are not connected anywhere, i.e. hanging in the air in the balloon itself! This is very clearly visible. 
In order not to bore the reader, I will immediately provide an electrical diagram. 
Just in case, I’ll duplicate the diagram at maximum resolution. There will also be a file with the firmware.
Next, for beginners, I will tell you in detail how the scheme works, and experienced ones will correct me if there is anything wrong.
1. Microcontroller
A microcontroller in a DIP package is responsible for the operation of the circuit; it controls the indicator driver and the anode voltage unit, receives data from the “clock” microcircuit, and an encoder is also connected to it to control the clock. Be careful, the pinout will be different when used in a TQFP package. If desired, you can replace the Atmega328P-PU with an Atmega168PA; there is enough memory, but I took it with a reserve for future firmware (currently it is 11.8 KB). Also, instead of a “naked” atmega, you can notice an Arduino, in this case you need to look at the pin mapping (which digital input/output corresponds to the pin on the microcontroller). In this circuit, the controller is switched on as standard; it operates at a frequency of 16 MHz from an external quartz resonator. Accordingly, the fuses are equal:
Low Fuse 0xFF, High Fuse 0xDE, Extended Fuse 0x05. Reset is connected to the power supply positive through a resistor. After correctly installing the fuses, the firmware was loaded via the ICSP block (SCK, MOSI, MISO, RESET, GND, Vcc).
2. Food
The 9V input voltage goes to the linear stabilizer and is reduced to 5V. This voltage is necessary to power the “digital logic”; it is supplied to the microcontroller and the MAX6921 driver. Because Our microcontroller operates at a frequency of 16 MHz, then the recommended voltage (based on the datasheet) is 5V. The stabilizer connection circuit is standard; instead of L7805, you can use any other one, even KR142EN5.
The circuit also requires a 3.3 V power supply, for this I used a stabilizer. This voltage powers the DS3231 “clock” microcircuit and the filament for the indicator. The connection diagram is based on the datasheet of the stabilizer.
Here I would like to draw your attention to a couple of points:
1. From the description of IV-18 it follows that the filament voltage is from 4.7 to 5.5 V, and in many circuits 5 V is supplied, for example, as in the Ice Tube Clock. In fact, visible glow occurs already at 2.7 V, so I consider 3.3 V optimal. When setting the watch to maximum brightness, the glow level is very decent. I suspect that by powering the indicator with this voltage, you will significantly extend its service life.
2. For a uniform glow, either an alternating voltage or a rectangular signal source is applied to the filament. In general, the work showed that when eating “constant” there is no effect of unevenness (I didn’t see it), so I didn’t bother.
To obtain the anode voltage, a simple step up converter circuit was used, which consists of inductor L1, field-effect transistor, Schottky diode and capacitor C8. I’ll try to explain how it works; to do this, let’s imagine the diagram as follows:
First stage 
Second phase 
The converter operates in two stages. Let's imagine that transistor VT1 acts as switch S1. At the first stage, the transistor is open (the key is closed), the current from the source passes through the inductor L, in the core of which energy is accumulated in the form of a magnetic field. At the second stage, the transistor is closed (the switch is open), the stored energy in the coil begins to be released, and the current tends to be maintained at the same level as it was at the moment the switch was opened. As a result, the voltage in the coil jumps sharply, passes through the diode VD and accumulates in capacitor C. Then the switch is closed again, and the coil begins to receive energy again, while the load is “powered” by capacitor C, and the diode VD does not allow the current to flow back into the power source. The stages are repeated one after another, preventing the capacitor from becoming empty.
The transistor is controlled by rectangular pulses with regulation from a PWM microcontroller, thereby you can change the charging time of capacitor C. The longer the charging time, the higher the voltage at the load. There is a tool on the Internet for calculating the output voltage depending on the PWM frequency, inductance and capacitance.
Resistors R3 and R4 represent a divider, the voltage from which is supplied to the analog-to-digital converter (ADC) of the microcontroller. This is necessary to control the voltage on the anodes (no more than 70 V is allowed) and adjust the brightness. Information about the anode voltage is displayed on the indicator in one of the operating modes. For example, at 30 V, the voltage across the divider will be about 0.3 V. Why this particular divider ratio, you ask?! It’s all about the operating principle of the ADC, which consists in constantly comparing the incoming voltage with a “reference” reference voltage source (RV), while the input voltage to the ADC cannot be greater than the RV. The reference voltage source can be: the supply voltage of the microcontroller, the voltage applied to the Aref pin or internal. This circuit uses an internal ION, which is equal to 1.1 V. The voltage received from the divider will be compared with it.
3. Clock chip 
A chip from Dallas Semiconductor is used as a real-time clock. This is a high-precision real-time clock (RTC) with a built-in I2C interface, a temperature-compensated crystal oscillator (TCXO) and a quartz resonator in one package. Compared to traditional solutions based on quartz resonators, the DS3231 has up to five times greater timing accuracy in the temperature range from -40 C to +85 C. The connection is standard, carried out via the I2C bus, which is pulled up by resistors to the power supply positive. This microcircuit has a built-in temperature sensor, information from which we will take for a room thermometer. A CR2032 battery serves as a backup power source to ensure the clock does not reset when disconnected.
4. Encoder
This circuit uses an incremental encoder to set the clock and select the operating mode. It is advisable to use it with a built-in tact button. The principle of operation is that the encoder produces pulses (“ticks”) when the knob is turned. Our task is to catch these “ticks” using the microcontroller. In this case, a short-term ground fault occurs. To suppress contact bounce, internal pull-up resistors μ, as well as 0.1 μF capacitors, are used. Also note that the encoder is connected to the external interrupt pins (INT), this is important.
5. Indicator and driver
The IV-18 indicator is a radio tube - a triode with a directly heated cathode, control grids (operating from the “plus” power supply) and a bunch of anodes with a luminescent coating. Above each group of anode segments (a, b, c, d, e, f, g) there is a separate grid.
The principle of indicating the number of one of the digits is as follows: the electric field of the control grid accelerates electrons, which, flying through a thin grid, reach those anode segments to which anode voltage is applied. Electrons hitting the phosphor cause it to glow.
To output a digit of one digit, it is enough to apply voltage to the corresponding anode segments and the grid. This will be a static display. To light up all the numbers in each digit, it is necessary to use a dynamic indication, because Anode segments in all discharges of the same name are interconnected and have common terminals. The grid for each digit has its own separate output.
Anode segments and grids can be controlled by an assembly of transistor switches, or by a special driver microcircuit. 
The chip is a high-voltage shift register that has 20 outputs with a permissible voltage of 76 V and a current of up to 45 mA. Data input is carried out via a serial interface. CLK - clock input, DIN - serial data input, LOAD - loading data, BLANK - turning off outputs, DOUT - intended for cascade connection of the same microcircuits. BLANK is pulled to the ground, i.e. the driver will always be enabled.
The MAX6921 operates in a similar way to the 74HC595 shift register. When the CLK clock input is logic 1, the register reads a bit from the Din data input and writes it to the least significant bit. When the next pulse arrives at the clock input, everything is repeated, only the bit recorded earlier is shifted by one bit (starting from OUT19 to OUT0), and its place is taken by the newly arrived bit. When all 20 bits are filled and the twenty-first clock pulse arrives, the register begins to fill again from the least significant bit and everything repeats again. In order for data to appear at the outputs OUT0...OUT19, you need to apply a logical one to the LOAD input.
There is one caveat with the microcircuit MAX6921AWI, there is a similar MAX6921AUI - it has a completely different pinout!!!
I’ll give a table of correspondence between the driver and indicator pins; it’s easier and clearer to assemble this way than to trace the electrical connections on the diagram. 
We're done with theory, let's move on to practice. Before making a printed circuit board, I first assemble it on a breadboard. After all, you always have to add something, modify it, check operating modes, etc.
View from above 
View from below. This picture is not for the faint of heart, it turned out to be a noble “dzhigurda”. 
We put on the cambrics and install the indicator in a separate board. 
Let's put it together. 
In operation they look like this. Photographed without external lighting, matrix noise is visible. 
Under the spoiler there will be information about all operating modes.
Clock menu
The menu is entered by turning or pressing the encoder. Exit - via the EXIT parameter, or automatic exit after 10 seconds.
Setting the time 
Setting the date 
For example: month November 
Day 20 
Year 2016 
Menu display for setting the display mode of date, time, temperature. 
Hours-minutes-seconds 
Hours-minutes-day 
Hours-minutes-temperature 
Month-day 
Hours-minutes-anode voltage 
Adjusting the Brightness Level 
From 1 to 7 
Bank mode. It has two states: on and off. If enabled, alternate display of time (in the format configured above), date and temperature. 
Exit menu 
Electrical tests
At minimum brightness: anode voltage 21.9 V, VT1 gate 1.33 V.
At maximum brightness: anode voltage 44.7 V, gate VT1 3.11 V.
The filament current of the indicator is 56.8 mA, the total current consumption of the clock is 110.8 mA.
Conclusion and thoughts for the future
What I want to do:
- Disconnect the printed circuit board
- Invent and make a designer case
- Add an outdoor temperature sensor
- Add interactivity to the clock, because... MK has a free uart, you can connect bluetooth and transfer any information, you can connect an esp and parse sites with weather, exchange rates, etc. The potential for modernization is very large.
In general, there is something to think about/work on. I am ready to listen to criticism and also answer questions in the comments. I'm planning to buy +53 Add to favorites I liked the review +194 +317
Clock circuit with fluorescent lamps
Many people want and are interested circuit diagram of a clock using vacuum indicators old Soviet times. Well, of course there is a lot of interesting things in this. Watch in retro style, and at night you can see what time it is. You can also insert diodes under the bottom, and it will be like a hint. And so let’s begin to consider this circuit.
The main role is occupied by gas discharge indicators. I used IV-6. This is a luminescent seven-segment indicator with a green glow (In the photographs you will see a bluish tint of the glow, this color is distorted when photographing due to the presence of ultraviolet rays). The IV-6 indicator is made in a glass flask with flexible leads. Indication is carried out through the side surface of the cylinder. The anodes of the device are made in the form of seven segments and a decimal point.
Can be applied indicators IV-3A, IV-6, IV-8, IV-11, IV-12 or even IV-17 with minor changes to the design.
First of all, I would like to note where you can find lamps that were produced in 1983.
Mitinsky market. Many and different. In boxes and on boards. There is room for choice.
It’s more difficult in other cities, maybe you’ll be lucky and you’ll find it in a local radio store. Such indicators are found in many domestic calculators.
You can order from Ebay, Yes Yes, Russian indicators at auction. On average $12 for 6 pieces.
Control
Everything is controlled by the AtTiny2313 microcontroller and the DS1307 real-time clock.
The clock, in the absence of voltage, switches to power mode from a CR2032 battery (as on a PC motherboard).
According to the manufacturer, in this mode they will work and will not fail for 10 years.
The microcontroller operates from an internal 8 MHz oscillator. Don't forget to set the fuse bit.
Setting the time is done with one button. Long hold, incriminating hours, then incriminating minutes. There are no difficulties with this.
Drivers
I used KID65783AP as keys for the segments. These are the 8 “top” keys. I made a choice towards this microcircuit only because I had it. This microcircuit is very often found in display boards for washing machines. Nothing prevents you from replacing it with an analogue one. Or pull up the segments with 47KOhm resistors to +50V, and press the popular ULN2003 to the ground. Just don’t forget to invert the output to the segments in the program.
The display is made dynamic, so a brutal KT315 transistor is added to each digit.
Printed circuit board
The payment was made using the LUT method. The clock is made on two boards. Why is this justified? I don’t even know, I just wanted it that way.
power unit
Initially the transformer was 50Hz. And contained 4 secondary windings.
1 winding - voltage on the grid. After the rectifier and capacitor 50 volts. The larger it is, the brighter the segments will glow. But no more than 70 volts. Current not less than 20mA
Winding 2 - to shift the grid potential. Approximately 10-15 volts. The smaller it is, the brighter the indicators glow, but the “not turned on” segments begin to glow just as brightly. The current is also 20mA.
Winding 3 - for powering the microcontroller. 7-10 volts. I = 50mA
4 winding - Heat. For four IV-6 lamps, you need to set the current to 200mA, which is approximately 1.2 volts. For other lamps, the filament current is different, so take this point into account.
Schematic diagram of a homemade watch using K176IE18, K176IE13 microcircuits and IV-11 luminescent indicators. A simple and beautiful homemade product for the home. A diagram of the clock, drawings of printed circuit boards, as well as a photo of the finished device in assembled and disassembled form are provided.
I offer for review and possible repetition this watch design on Soviet IV-11 luminescent indicators. The circuit (shown in Figure 1) is quite simple and, if assembled correctly, starts working immediately after switching on.
Schematic diagram
The electronic clock is based on the K176IE18 chip, which is a specialized binary counter with a generator and a multiplexer. Also, the K176IE18 microcircuit includes a generator (pins 12 and 13), which is designed to work with an external quartz resonator with a frequency of 32,768 Hz; the microcircuit also contains two frequency dividers with division factors 215 = 32768 and 60.
The K176IE18 microcircuit contains a special audio signal generator. When a pulse of positive polarity is applied to the input pin 9 from the output of the K176IE13 microcircuit, packs of negative pulses with a filling frequency of 2048 Hz and a duty cycle of 2 appear at pin 7 of the K176IE18.
Rice. 1. Schematic diagram of a homemade watch with IV-11 luminescent indicators.
The duration of the packs is 0.5 seconds, the filling period is 1 second. The audio signal output (pin 7) is made with an “open” drain and allows you to connect emitters with a resistance of more than 50 Ohms without emitter followers.
I took as a basis the schematic diagram of an electronic clock from the site "radio-hobby.org/modules/news/article.php?storyid=1480". During assembly, significant errors were discovered by the author of this article in the printed circuit board and the numbering of some pins.
When drawing a pattern of conductors, it is necessary to flip the signet horizontally in a mirror version - another disadvantage. Based on all this, I corrected all the errors in the signet layout and translated it immediately in mirror image. Figure 2 shows the author's printed circuit board with incorrect wiring.
Rice. 2. Original printed circuit board containing errors.
Figures 3 and 4 show my version of the printed circuit board, it is corrected and mirrored, viewed from the side of the tracks.
Rice. 3. Printed circuit board for the clock circuit on IV-11, part 1.
Rice. 4. Printed circuit board for the clock circuit on IV-11, part 2.
Changes in the scheme
Now I’ll say a few words about the circuit; when assembling and experimenting with the circuit, I encountered the same problems as the people who left comments on the article on the author’s website. Namely:
- Heating of zener diodes;
- Strong heating of transistors in the converter;
- Heating of quenching capacitors;
- Heat problem.
Ultimately, the quenching capacitors were composed of a total capacitance of 0.95 μF - two capacitors 0.47x400V and one 0.01x400V. Resistor R18 has been replaced from the indicated value in the diagram to 470k.
Rice. 5. Appearance of the main board assembly.
Zener diodes used - D814V. Resistor R21 in the converter bases was replaced with 56 kOhm. The transformer was wound on a ferrite ring, which was removed from the old connecting cable between the monitor and the computer system unit.
Rice. 6. Appearance of the main board and the board with indicators assembled.
The secondary winding is wound with 21x21 turns of wire with a diameter of 0.4 mm, and the primary winding contains 120 turns of wire with a diameter of 0.2 mm. These are, however, all the changes in the scheme that made it possible to eliminate the above-mentioned difficulties in its operation.
The transistors of the converter get quite hot, about 60-65 degrees Celsius, but they work without problems. Initially, instead of transistors KT3102 and KT3107, I tried to install a pair of KT817 and KT814 - they also work, a little warm, but somehow not stable.
Rice. 7. Appearance of the finished watch on luminescent indicators IV-11 and IV-6.
When turned on, the converter started up every other time. Therefore, I did not redo anything and left everything as is. As an emitter, I used a speaker from some cell phone that caught my eye, and installed it in the watch. The sound from it is not too loud, but enough to wake you up in the morning.
And the last thing that can be considered a disadvantage or an advantage is the option of transformerless power supply. Undoubtedly, when setting up or any other manipulations with the circuit, there is a risk of getting a serious electric shock, not to mention more dire consequences.
During experiments and adjustments, I used a step-down transformer with 24 volts of alternation on the secondary. I connected it directly to the diode bridge.
I didn’t find any buttons like the author’s, so I took the ones I had on hand, stuck them into the machined holes in the case, and that’s it. The body is made of pressed plywood, glued with PVA glue and covered with decorative film. It turned out quite well.
The result of the work done: another clock at home and a corrected working version for those who want to repeat it. Instead of IV-11 indicators, you can use IV-3, IV-6, IV-22 and other similar ones. Everything will work without problems (taking into account the pinout, of course).
There was an idea to create a clock using IV lamps; in the bins there were five new IV-11 lamps and the same number of IV-6 lamps, all that remained was to use them.
What should the watch contain?
1. Current time;
2. Alarm clock;
3. Built-in calendar (we take into account the number of days in February, including in a leap year) + calculation of the day of the week;
4. Automatic adjustment of indicator brightness;
5. Sound signal every hour.
Here are the main components of any watch. Adjusting the brightness is necessary because IV lamps shine normally during the day, but at night they are very bright and blind, especially at night when you are sleeping.
Clock diagram
There is nothing new or supernatural in the circuit: a DS1307 real-time clock, dynamic display, several control buttons, all controlled by ATmega8.
To measure the illumination in the room, a photodiode FD-263-01 was used, as the most sensitive one available. True, it has a small problem with spectral sensitivity - the peak of sensitivity is in the infrared range and, as a result, it senses the light of the sun/incandescent lamps very well, and fluorescent lamps/LED lighting - a C grade.
Anode/grid transistors - BC856, PNP with a maximum operating voltage of 80V.
To indicate seconds, the IV-6 is smaller in size, since it has a lower filament voltage - a 5-10 Ohm quenching resistor helps it.
For the alarm signal there is a piezo emitter with a built-in 5V generator.
From the power supply, the entire circuit consumes +9V up to 50mA along the line, the heat is 1.5V 450mA, the heat relative to the ground is at a potential of -40V, consumption is up to 50mA. Total total maximum 3W.
The accuracy of the DS1307 quartz oscillator leaves much to be desired - after washing the board and selecting the quartz piping containers, we managed to achieve something like +/-2 seconds per day. More precisely, the frequency fluctuates depending on temperature, humidity and the position of the planets - not at all what we wanted. After thinking a little about the problem, I decided to order a DS32KHZ microcircuit - a fairly popular temperature-compensated quartz oscillator.
It’s not for nothing that the generator is so expensive - according to the reference book, the manufacturer promises to increase the accuracy of the clock to +/- 0.28 seconds per day. In reality, under acceptable power conditions and temperature ranges, I was not able to see a change in frequency due to external factors.
After assembling the case and “combing” the firmware, the watch has 3 buttons left: let’s call them “A” “B” “C”.
In the normal state, the "C" button is responsible for switching the mode from displaying the time "hours - minutes" to the date "day - month", the second indicator displays the day of the week, then by year, then to the "minutes - seconds" mode, in the fourth pressing - to the original state. Button "A" quickly switches to the time display.
From the “hours - minutes” mode, button “A” switches in a circle to the “alarm clock setting” / “time and date setting” / “indicator brightness setting” mode. In this case, the “B” button switches between digits, and the “C” button actually changes the selected digit.
“Alarm setting” mode, the letter A (Alarm) on the middle indicator means that the alarm is on.
Mode “setting time, date” - when the “seconds” digit is selected, the “C” button rounds them (from 00 to 29 resets them to 00, from 30 to 59 resets them to 00 and adds +1 to the minute).
In the “time and date setting” mode, at the SQW output of m/s DS1307 there is a meander of 32.768 kHz - necessary when selecting quartz/capacitors for the generator; in other modes it is 1Hz.
Before turning on the clock, you need to select the current flowing through the filaments, it is adjusted visually so that the filaments on all lamps in the dark are slightly red, so they will live longer
Mode "adjusting the brightness of the indicator": "AU" - automatic, shows the measured illumination in units. ;) "US" - manual setting in the same units.
DS1307 and DS32KHZ are powered by a CR2032 battery and when the power is lost, the time does not stop, but continues to run, only the Mega8 and all its hardware with indicators are turned off, and the stabilized quartz and real-time clock continue to work, they consume extremely little and the batteries should last for a very long time for a long time.
The brightness can be adjusted either manually or automatically, since a simple photodiode did not suit me in terms of its parameters, I had to sculpt a photo relay according to the diagram below:
any photodiode, I used FD-K-155, a tuning resistor is needed to determine the brightness of the response, instead of a relay you need to install a low-voltage reed relay, from its common terminals we connect to the common wire of the clock, and the other two through variable resistors 10-500 kOhm instead of a photodiode to the port PC0 of the controller, so the resistor will replace the photodiode and with a certain value of the resistor you can adjust the brightness you need, which will be day and night when the photo relay operates.
ATmega8 fuses for internal 8 MHz oscillator:
Here's what actually happened in the hardware:
lower part of the case with hidden buttons and a hole for the speaker
separate photo relay board
Schematic diagram of a homemade watch using K176IE18, K176IE13 microcircuits and IV-11 luminescent indicators. A simple and beautiful homemade product for the home. A diagram of the clock, drawings of printed circuit boards, as well as a photo of the finished device in assembled and disassembled form are provided.
I offer for review and possible repetition this watch design on Soviet IV-11 luminescent indicators. The circuit (shown in Figure 1) is quite simple and, if assembled correctly, starts working immediately after switching on.
Schematic diagram
The electronic clock is based on the K176IE18 chip, which is a specialized binary counter with a generator and a multiplexer. Also, the K176IE18 microcircuit includes a generator (pins 12 and 13), which is designed to work with an external quartz resonator with a frequency of 32,768 Hz; the microcircuit also contains two frequency dividers with division factors 215 = 32768 and 60.
The K176IE18 microcircuit contains a special audio signal generator. When a pulse of positive polarity is applied to the input pin 9 from the output of the K176IE13 microcircuit, packs of negative pulses with a filling frequency of 2048 Hz and a duty cycle of 2 appear at pin 7 of the K176IE18.
Rice. 1. Schematic diagram of a homemade watch with IV-11 luminescent indicators.
The duration of the packs is 0.5 seconds, the filling period is 1 second. The audio signal output (pin 7) is made with an “open” drain and allows you to connect emitters with a resistance of more than 50 Ohms without emitter followers.
I took as a basis the schematic diagram of an electronic clock from the site "radio-hobby.org/modules/news/article.php?storyid=1480". During assembly, significant errors were discovered by the author of this article in the printed circuit board and the numbering of some pins.
When drawing a pattern of conductors, it is necessary to flip the signet horizontally in a mirror version - another disadvantage. Based on all this, I corrected all the errors in the signet layout and translated it immediately in mirror image. Figure 2 shows the author's printed circuit board with incorrect wiring.
Rice. 2. Original printed circuit board containing errors.
Figures 3 and 4 show my version of the printed circuit board, it is corrected and mirrored, viewed from the side of the tracks.
Rice. 3. Printed circuit board for the clock circuit on IV-11, part 1.
Rice. 4. Printed circuit board for the clock circuit on IV-11, part 2.
Changes in the scheme
Now I’ll say a few words about the circuit; when assembling and experimenting with the circuit, I encountered the same problems as the people who left comments on the article on the author’s website. Namely:
- Heating of zener diodes;
- Strong heating of transistors in the converter;
- Heating of quenching capacitors;
- Heat problem.
Ultimately, the quenching capacitors were composed of a total capacitance of 0.95 μF - two capacitors 0.47x400V and one 0.01x400V. Resistor R18 has been replaced from the indicated value in the diagram to 470k.
Rice. 5. Appearance of the main board assembly.
Zener diodes used - D814V. Resistor R21 in the converter bases was replaced with 56 kOhm. The transformer was wound on a ferrite ring, which was removed from the old connecting cable between the monitor and the computer system unit.
Rice. 6. Appearance of the main board and the board with indicators assembled.
The secondary winding is wound with 21x21 turns of wire with a diameter of 0.4 mm, and the primary winding contains 120 turns of wire with a diameter of 0.2 mm. These are, however, all the changes in the scheme that made it possible to eliminate the above-mentioned difficulties in its operation.
The transistors of the converter get quite hot, about 60-65 degrees Celsius, but they work without problems. Initially, instead of transistors KT3102 and KT3107, I tried to install a pair of KT817 and KT814 - they also work, a little warm, but somehow not stable.
Rice. 7. Appearance of the finished watch on luminescent indicators IV-11 and IV-6.
When turned on, the converter started up every other time. Therefore, I did not redo anything and left everything as is. As an emitter, I used a speaker from some cell phone that caught my eye, and installed it in the watch. The sound from it is not too loud, but enough to wake you up in the morning.
And the last thing that can be considered a disadvantage or an advantage is the option of transformerless power supply. Undoubtedly, when setting up or any other manipulations with the circuit, there is a risk of getting a serious electric shock, not to mention more dire consequences.
During experiments and adjustments, I used a step-down transformer with 24 volts of alternation on the secondary. I connected it directly to the diode bridge.
I didn’t find any buttons like the author’s, so I took the ones I had on hand, stuck them into the machined holes in the case, and that’s it. The body is made of pressed plywood, glued with PVA glue and covered with decorative film. It turned out quite well.
The result of the work done: another clock at home and a corrected working version for those who want to repeat it. Instead of IV-11 indicators, you can use IV-3, IV-6, IV-22 and other similar ones. Everything will work without problems (taking into account the pinout, of course).
Printed circuit board and diagram (original from the site) - (80KB).
