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Lap Stopwatch with ATmega328 Microcontroller

This instructable will show you how to build your own stopwatch to record multiple splits using an ATmega328 programmable microcontroller. When one presses the start button (or slaps the metal band in my watch), the screen displays the last lap for a second then continues the time on the next lap. It’s great for all you runners out there doing an interval workout.

Needed Materials:
• Arduino Uno or Duemilanove
• ATmega328 microcontroller
• Computer to use Arduino
• breadboard
• Three buttons
• A switch
• Three resistors*
• 16 MHz crystal oscillator
• Two 22 pF capacitors
• Adafruit SSD1306 128X32 LCD screen**
• Two AA batteries**
• Soldering iron and soldering board
• Wires
• Wristband
• Encasing

Optional but Useful:
• Hot Glue gun
• Super glue
• Wire strippers
• Multimeter
• Acetal Polymer
• Blue tempered spring steel

*I used 10 kΩ, but the value doesn’t matter too much, as it is just used to stabilize the voltage so it drops quickly when the buttons are no longer pressed.

Lap Stopwatch with ATmega328 Microcontroller

**I realized later on that this lcd screen needs 20mA of current, but a regular coin battery that can only provide .19 mA, so I had to use two AA batteries to meet the current demand. I would suggest looking for a more compact battery that can provide at least 3 V but less than 5V and more current such as some camera batteries. Either that or try to find a different lcd screen, but then the code will need to be modified. As of now, this lcd can be bought at (


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