$5 Arduino Clock

Create an Arduino compatible clock inexpensively. This project is fun and easy to duplicate. It can be put into the enclosure or project of choice. I used a plastic electronics parts kit box. The base parts cost $5, but it also needs micro USB power. The sketch coded for 24 hour time.

Part List - Links to AliExpress

• ATtiny85 Digispark
• LED Display Module
• RTC Module
• Jumper Cables
• CR2032 Battery

Digispark needs a USB driver installed. Instructions for Windows 7 - 10

Add Arduino IDE board support for Digispark

Go to the "File" menu and select "Preferences"
In the box labeled “Additional Boards Manager URLs” enter: http://digistump.com/package_digistump_index.json and click OK

Go to the “Tools” menu and then the “Board” select “Boards Manager” and then from the type drop down select “Contributed”: Select the “Digistump AVR Boards” package and click the “Install” button.

After install completes, close the “Boards Manager” window and select “Digispark (Default - 16.5mhz)” from the Tools→Boards menu.

Go to Sketch, Include Library, then Manage Libraries. Make sure the following libraries are installed: tm1637 (Grove 4-Digit Display)

Open the sketch file and set the correct time on the rtc.adjust line. The numbers are: (Year, Month, Day, Hour, Minute, Second)

These Digispark style development boards work differently than Arduino boards. You will first hit upload then plug in the board when prompted. They are programmable for a few seconds after plugged in.

You will need to do some light soldering to install the pin headers onto the modules.

• Put CR2032 battery in in DS3231 RTC module
• Connect jumper wire from P0 to SDA on the RTC module
• Then connect P2 to SCL on RTC module
• Connect P3 to CLK on TM1637 Display module
• Then P4 to DIO on Display module
• Connect VCC and Ground to RTC module then VCC and Ground on other side to the display module.

All done! You can power it now. You can use a micro USB AC adapter or battery pack.