World Clock LED Matrix Display

WorldClock is a world clock display for MAX7219 or MAX7221 LED matrix display controllers using Arduino. It was built using D1 Mini Pro and 2 MAX7219 32x8 units connected together, however it can easily be adjusted to other controllers, other displays in other sizes.

Functionality

World Clock

WorldClock will rotate between multiple timezones (configurable) and will display the time in each. It uses an NTP service to get the accurate time, including Daylight Saving offset if applicable. It will refresh the results every 24 hours.

MQTT Support

There is also (optional) support for MQTT for receiving messages, which will then be displayed in higher brightness to attract attention. If enabled, WorldClock will subscribe to topic <devicename>/message/command where devicename is the name of the device in the configuration (see below).

Hardware and Assembly

Please refer to any of the many tutorials that are available to assemble your setup based on the components you chose.

Configuration

For configuration edit the sketch prior to uploading it to your controller.

Locations

To configure the list of locations to be displayed, you will need to initialize a new 'location' struct and add it to the locations array. See the example below.

In the following example the clock will rotate between London and Kenya.

• The first member is the timezone label in London. For the valid list of timezones see http://worldtimeapi.org/api/timezone.
• The second member is the label to be display in the clock. It does not need to match the timezone label.
• Keep the third member -1 (it is automatically initialized and maintained).

struct location {
  char* timezone;
  char* timezoneLabel;
  int utcOffsetInSeconds;
};

location locations[] = {
  { "Europe/London", "London", -1 },
  { "Africa/Nairobi", "Nairobi", -1 }
};

Note The first entry is considered your local time and all other locations are compared to that for the purpose of specifying +1 / -1 to indicate Tomorrow / Yesterday respectively.

Wifi

The following configuration parameters are defined in secrets.h.

• SECRET_SSID - the name of your WiFi SSID.
• SECRET_PASS - the password for you WiFi.

Other

• MQTT_HOSTNAME - the hostname of your MQTT server. This parameter is defined in secrets.h.
• deviceName - the hostname for the device. This is also used as the prefix for the MQTT topic if used.
• HARDWARE_TYPE - the type of MAX7219 unit you are using. Default MD_MAX72XX::FC16_HW
• MAX_DEVICES - the number of 8x8 devices that will be in use.
• CS_PIN, CLK_PIN, DATA_PIN - the SPI pins used by the controller. Note that if using hardware SPI you will only need to set the CD_PIN.
• INTENSITY_NORM - the display intensity for normal use (clock view).
• INTENSITY_ALERT - the display intensity for alerts (MQTT).

Credits

• WorldClock uses the wonderful MD_Parola library https://github.com/MajicDesigns/MD_Parola,
• For free timezone data: http://worldtimeapi.org