Digital Output: LEDs and Relays in MicroPython

💡 Digital Output with MicroPython - LED & Relay Control

💡 What You'll Learn:

🔌 Control LEDs, relays, and pumps with MicroPython
💧 Automate water pumps based on soil moisture
⚡ Understand active LOW vs active HIGH relays

🔧 Basic LED Control

from machine import Pin
import time

# LED on GP0 with 220Ω resistor
led = Pin(0, Pin.OUT)

while True:
    led.on()      # LED ON
    print("🔴 LED ON")
    time.sleep(1)
    
    led.off()     # LED OFF
    print("⚫ LED OFF")
    time.sleep(1)

💧 Relay Control for Water Pump

from machine import Pin
import utime

# Relay on GP1 (most 5V relays are ACTIVE LOW)
relay = Pin(1, Pin.OUT)
relay.value(1)     # Start with pump OFF (HIGH = OFF for active LOW)

def water_pump(seconds):
    print(f"💧 Watering for {seconds} seconds...")
    relay.value(0)      # LOW = pump ON
    utime.sleep(seconds)
    relay.value(1)      # HIGH = pump OFF
    print("✅ Watering complete")

# Example: water if soil is dry
soil_moisture = 25  # Replace with sensor reading
if soil_moisture < 30:
    water_pump(10)      # Water for 10 seconds

💡 MicroPython vs Arduino:

MicroPython: led.on() / led.off() or led.value(1/0)

Arduino: digitalWrite(pin, HIGH/LOW)

Most 5V relays are ACTIVE LOW: value(0) = ON, value(1) = OFF

⚠️ Important:

Always use a resistor (220Ω) with LEDs to prevent damage

Never connect a pump directly to Pico - use a relay!

Test your relay: if ON when value(0), it's active LOW

🎉 Quick Reference:

Pin(pin, Pin.OUT) → Set as output

.on() / .off() → Turn on/off

.value(1) / .value(0) → Set HIGH/LOW

utime.sleep(seconds) → Delay (non-blocking sleep)

💡 Key Takeaways:

Apply these concepts directly to your farm or project.

Take notes on important details for the quiz.

Use the button below to track your progress.

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