Water Sump Pump Countdown Timer

A countdown timer for managing a water sump pump using a Raspberry Pi Pico programmed in MicroPython, designed for SLAC National Accelerator Laboratory during Summer 2024.

• Features: Automates sump pump intervals and relay activation with a 60-minute countdown timer, 3-button control (START/STOP/RESET), and thermal safety from 80°F fan activation to prevent overheating
  • Each button (START/STOP/RESET) is mapped to an LED and activates a specific state when the user presses on it
  • 60-minute countdown timer displayed in MM:SS format with the temperature on the LCD (Countdown: 60:00 & Temp: 80 F)
  • LCD Library from RPI-PICO-I2C-LCD by T-622: lcd_api & pico_i2c_lcd
• Components: Full BOM with relay and sump pump specs

Schematics¹²

SLAC Water Sump Pump Countdown Timer Schematic

RP2040 Water Sump Pump Countdown Timer Schematic

Relay Behavior

Relay controls the 120 VAC outlet like a feedback loop.

• SLAC Water Sump Pump Countdown Timer Schematic: Pin 3 from K1 relay has an input of 120 VAC L input (10 A) and Pin 4 is an input to the same 120 VAC output
• START: Relay NC³ → Sump pump activates
• STOP & RESET: Relay NO³ → Sump pump deactivates

START/STOP/RESET Button Controls

START/STOP/RESET Button State Diagram

               ┌──────────────────────────┐
               │                          ▼
┌────┐   ┌─────┴───┐   ┌────────┐   ┌─────────┐
│Idle├──►│START Btn├──►│STOP Btn├──►│RESET Btn│
└────┘   └─────────┘   └────┬───┘   └────┬────┘
              ▲             ▼            │
              └──────────────────────────┘

START Button

• Function: Default state where the system starts 60-minute countdown timer
• LED: Blinking green

STOP Button

• Function: Pauses the countdown timer

• LED: Solid red

• LCD: Displays messages repeatedly

  Countdown stopped!

  Press START or RESET

• countdown_stop = True pauses the countdown timer

START & RESET Button on STOP

• START: Countdown timer continues from the time it was paused on
  • LED: Red off and blinking green

RESET Button

• Function: Emergency reset (Countdown timer restarts at 60:00 after the user presses START button)

• LED & Buzzer Blinking blue & buzzer beeps repeatedly

• LCD: Displays messages repeatedly

  Countdown reset!

  Press START to start over

• system_locked = True allows the user one button to press on to restart the countdown timer

  • User can press on STOP or RESET button, but the program ignores the two button presses when in RESET mode

Countdown Idle and Completion LCD Messages

• Countdown Idle: Press START!
• Countdown Completion: Press START to start agn

Notes

• SLAC Water Sump Pump Countdown Timer Schematic: A K1 relay is connected to the L298N motor driver, which is the component connected in the final hardware
• RP2040 Water Sump Pump Countdown Timer Schematic: A 5V DC motor is used since the relay acts like a switch along with an IC2 1602 LCD connected to the RP2040
  • Ex: Motor on when countdown timer is running and vice versa when it is off
• Power Indicator: Green LED stays on during both idle and after completion states to indicate that the Pi Pico is powered

Credit

• LCD Library: Adapted from RPI-PICO-I2C-LCD by T-622

Footnotes

1. SLAC Water Sump Pump Countdown Timer Schematic and .kicad_sch ↩

2. RP2040 Water Sump Pump Countdown Timer Schematic and .kicad_sch ↩

3. Normally open (NO) & normally closed (NC) ↩ ↩²