Retro clock with alarm and DHT22 (temperature and humidity sensor) based on Soviet Union IN-14 (NIXIE in USA) indicators. Firmware and PCB.

First of all, my project is based on two Alex Gyver's projects: NixieClock and NixieClock_v2. Which in turn are based on Andrey Zhelezniakov's project. Which in turn is based on "Elisa" project... And so on) I took project of Alex and just fixed some bugs, added alarm function and DHT sensor support. Alex made a lot of work. His "glitches" effect is awesome! Maybe only it inspired me to repeat his project and add some stuff for myself.

A lot of useful information could be found here.

About

The clock is driven by Arduino Nano v3.0 with ATmega328. It would be great to replace it with microcontroller (but my ISP programmer doesn't work, I have no time... and I'm lazy).

• The board power supply: 5V.
• Antioxidation procedure every 30 mins.
• 2 modes of brightness: day and night modes. The brightness of digits and backlight changes depending on time.
• 3 modes of indicators backlight.
• 7 modes of digit change - "flip effects".
• "glitches" - really cool effect by Alex Gyver. Indicators flicker randomly. It looks ominously)
• 2 variants of alarm: with and without toggle switcher. In the latter case, if you do not need the alarm, it should be set to 24 hour (not 00, exactly 24). Or you can use toggle switch between GND and pin 13 (by default). Grounded pin 13 means the alarm is set. To disable alarm, just cut pin 13 from GND.
• 2 types of buzzer: active and passive. While passive buzzer being used, the frequency could be generated with PWM or with main loop (more details are in source code).
• All settings are stored in EEPROM.
• DHT22 sensor support. By default clock shows time for 10 seconds ("show time" mode) and temperature and humidity for 3 seconds ("show temp/hum" mode).
• Minimum clearance is 0.5 mm for high voltage nets and 0.254 mm (0.4 mm almost everywhere) for data nets.

Controls

Clock settings:

- Hold "SET" - switch between clock modes:
	0. "show clock", initial and main mode;
	1. "set alarm";
	2. "set clock".
- Click "SET" in "set alarm" and "set clock" modes - change between setting hours and minutes.
- Double click "SET" in "set alarm" mode - exit to "show clock" mode, skipping "set clock" mode.
- Click "SET" while alarm ringing - turn alarm off.

Effects settings: (should be done in "show clock" mode)

- Click "-" - change backlight mode:
	1. "breath";
	2. always on;
	3. off.
- Click "+" - change effect of digits' appearance (flip effect):
	1. no effect;
	2. smooth fading;
	3. rewind in order of number;
	4. rewind in order of cathode;
	5. train;
	6. elastic band;
	7. glitchy flip.
- Hold "-" - turn the "glitches" on/off.
- Hold "+" - turn the "show temp/hum" on/off.

Issues

[ ] 1. alarm security issue.

[ ] 2. replace #define with 'constexpr'.

1. Clock synchronizes with RTC every half an hour. Let clock is couple of minutes slow. So after synchronization, these couple of minutes will be skipped. The alarm could be set in these skipped time. Some checking flag and timer should be added. This situation is very unlikely since clock is quite precise. So I don't bother.

2. GCC compiler from Arduino toolchain supports standart 11 (and even 14) of C++, it would be more correct to use latest features.