Summary of 12-Multi National Digital Clock on Arduino UNO
This article details a cost-effective DIY project to build a 12-nation digital clock using an Arduino UNO. By leveraging a precise DS3231 RTC and multiple ILI9163 TFT displays connected via SPI, the system can show time and dates for up to twelve different countries simultaneously on elegant dials. The total cost for a 12-display setup is approximately $46, making it an affordable alternative to commercial hotel lobby clocks.
Parts used in the 12-Multi National Digital Clock:
- ATMega-328 / Arduino UNO microcontroller
- DS3231 Real Time Clock module
- 128*128 TFT displays (ILI9163)
- Jumper wires for connections
The presence of 12-Multi-National Digital clocks is very common at the lobby / front desk of star hotels, showing time & dates of several countries where from most of the guests to arrive to stay at the hotel. One common feature of these clocks is that they are majestically looking elegant dial clocks!
I tried to achieve that feature using a cheap ATMega-328 alias bare-minimum Arduino UNO microcontroller [which hardly costs $3 per piece], few cheap 128*128 TFT displays and an RTU DS3231.
The principle of operation:
The DS3231 is a very precise RTU which has an inbuilt temperature sensor for adjusting the clock frequencies for temperature corrections. It maintains very precise timings over long durations. DS3231 connects on I2C Bus.
Each TFT ILI9163 is a 128*128 dots color display runs on SPI bus along with Reset & AO pin and it needs only one extra GPIO pin per display to complete its connection with the Arduino. That is the crux of this cheap yet versatile multi-nation digital clock and the cost is $46 for 12-display system.
Let us see how?
Each TFT ILI9163 Runs on 5volt / 3.3volt and has the following pins – VCC, GND, LED, CS, RST, AO, SDK & SCK. Out of these VCC, GND, LED is common pins. The remaining pins can be common depending on the choice.
| ILI9163 Pins | Nature of pins | UNO pins | |||
| Disp-1 | Disp-2 | Disp-3 | Disp-4 | ||
| VCC | 5 volt / 3.3 volt | 5V / 3.3V | |||
| GND | Only Ground | Gnd | |||
| LED | 5 Volt / 3.3 Volt | 5V / 3.3V | |||
| CS | Must be different pins for each display | A1 | A2 | A3 | Digital pin 2 |
| Reset | Can be common or RES pin of UNO | RES pin of UNO | |||
| AO | Can be common or Different pins. | A0 | |||
| SDA | Fixed pin for all displays | Digital pin 11 | |||
| SCK | Fixed pin for all displays | Digital pin 13 | |||
| DS3231 Pins | UNO Pins |
| VCC | 5 Volt |
| GND | Gnd |
| SCL | A5 |
| SDA | A4 |
Using the above tables one can see that apart from 5 fixed / specific pins, for each UNO pin one can create one country-specific display. Like – A1, A2, A3, D2, D3, D4, D5, D6, D7, D8, D9, D10
Total 12 different national clock display can be created on one UNO!
* D0, D1 & D12 cannot be used as they are special purpose pins.
Schematic: [for 4 displays multi nation clock]
To add more displays, just repeat the connections.
Bill of Materials & Price for 4 displays a multi-nation clock
1 * DS3231 – $1
1 * ATMEGA328 / UNO – $3
4 * 128*128 TFT [ILI9163] – $14 [$3.5 a piece ]
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For 4 display multi-nation clock = $18; For 12 display multi-nation clock = $46
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The schematic is shown for 4 displays a multi-nation clock. To go up to 12 displays, to just add so many displays, repeat the connections and make necessary changes in the sketch.
Software
Prototype
Here I have just built up a 2-display-clock. To add more displays, Just follow the sketch, repeat the display connections & make necessary changes in the program sketch and you will be able to build your 12-nation-clock in no time.
Download source folder
Read More Detail:12-Multi National Digital Clock on Arduino UNO
- What is the main purpose of this project?
To create a multi-national digital clock showing time and dates for several countries, commonly found in hotel lobbies. - How many national clock displays can be created on one UNO?
A total of 12 different national clock displays can be created on one UNO. - What is the total cost for a 12-display system?
The cost is $46 for a 12-display system. - Which bus does the DS3231 connect to?
The DS3231 connects on the I2C Bus. - Which pins must be different for each display?
The CS pins must be different pins for each display. - Can the Reset and AO pins be shared?
Yes, the Reset and AO pins can be common or different depending on the choice. - Which Arduino pins cannot be used as display outputs?
D0, D1, and D12 cannot be used because they are special purpose pins. - How do you add more displays beyond four?
You just need to repeat the connections and make necessary changes in the program sketch.
