Pomodoro Timer

This simple project was requested by a client.

Step 1. Hardware time preset

Produce a Pomodoro Timer where you can set the working time and rest time

The client proposed a set of jumper headers to configure timers along with a sketch of the hardware.

Timers value are hardcoded

Working time

• 15 minutes
• 30 minutes
• 60 minutes
• 90 minutes

Relax time

• 0 min
• 5 min
• 10 min
• 15 min

A row of LED are used to display the state of the timers.

Step 2. Start timer

User clicks button to start timer

User hears sound from buzzer

LED progress bar turned on

• Logic of the LED progress bar
  • Countdown progress bar
    • Ex: 30 minutes timer
    • 10 LEDs are on
    • the last one 10th is flashing
    • Every 3 minutes (time/amount of leds) 1 led turn off, after 3 minutes only 9 are on, the 9th is flashing

Step 3. Timer is over

Once working timer is over:

• All progress bar LEDs flash
• Buzzer produce sound

Then User click button and Relax(Rest) timer began with the same logic

• Led progress bar has different color
• Once Rest timer finished - another melody is playing

To stop timer the User must hold the button pressed for 3 seconds.

No pause function needed

Power requirements

Ideally make it run from a tiny battery like CR2032 or 2-3 AAA Batteries.

Enclosure requirements

No enclosure or enclosure built from PCB

Size requirements

Less than 85 mm x 50mm

Proposal

• Use a lowcost pic16lf15355 SOIC 28 MCU which can be powered from 1.8v-5v, running from internal oscillator and able to idle at very low current.
• Use 7 red/green bi-color, low power LEDs
• Use 2 AAA Batteries in series at 2v-3v to extend runtime and reduce end user cost over lithium CR2032 cell.
• Use Microchip MPLAB-X, XC8 and Pickit5 for development.
• 67mm x 40mm board area, battery holder mounted on the back.

Completed Project

Working, partially populated board

Project revision

I recently started investigating the py32 series of microcontrollers from puya, these are very low cost ( 12cents, you read that correctly ) arm-cortex-m0 processors running at 24MHz. I ported the pomodoro firmware for the pic16 targeting the py32 controller and redsigned the board to support a tssop20 package. The new hardware is aimed at owering costs, along with the processor selection I opted for 14 leds in 0603 packages to reduce the cost. The complete BOM comes in at less than $1 and has feature parity with the original, supporting the same number of output and inputs as the original.