🚀 Project 2.8 – Basic Security System

🎯 What You’ll Learn

• ✅ Goal 1: Activate and deactivate a security system with an IR remote.
• ✅ Goal 2: Detect intruders using touch sensors.
• ✅ Goal 3: Detect impacts with crash sensors.
• ✅ Goal 4: Trigger different alarms depending on the sensor.
• ✅ Goal 5: Record events in the serial log.

Key Ideas

• Short definition: Security systems combine sensors and alarms to protect spaces.
• Real‑world link: Used in homes, cars, and robots to detect unauthorized access.

🧱 Blocks Glossary

• Touch sensor: tc2 = machine.TouchPad(machine.Pin(2)) → Detects touch input.
• Crash sensor: pin5 = machine.Pin(5, machine.Pin.IN) → Detects impact.
• IR remote: ir_rx = irremote.NEC_RX(18,8) → Reads remote codes.
• Buzzer: midi = music.MIDI(26) → Plays alarm sounds.
• Serial print: print("...") → Logs events.
• Loop: while True: → Continuous monitoring.
• if/else: Decide actions based on sensor input.

🧰 What You Need

🔌 Wiring tip: Connect IR receiver to pin 18, touch sensor to pin 2, crash sensor to pin 5, buzzer to pin 26.

✅ Before You Start

print("Ready!")  # Confirm serial is working

🎮 Microprojects (5 Mini Missions)

🎮 Microproject 2.8.1 – Remote activation/deactivation

Goal: Use IR remote to turn system ON/OFF.

MicroPython Code:

# Remote activation/deactivation
# This program uses IR remote to activate or deactivate the security system

import irremote, time                         # Import IR library and time

ir_rx = irremote.NEC_RX(18,8)                 # Setup IR receiver on pin 18
system_active = False                         # Start with system OFF

print("Security system ready")                # Serial start message

while True:                                   # Infinite loop
    if ir_rx.any():                           # If IR signal received
        code = ir_rx.code[0]                  # Read code
        if code == 0xA90:                     # Example ON button
            system_active = True              # Activate system
            print("System activated")         # Serial confirmation
        elif code == 0xA91:                   # Example OFF button
            system_active = False             # Deactivate system
            print("System deactivated")       # Serial confirmation
    time.sleep(0.1)                           # Delay for stability

Reflection: You can now control system ON/OFF with remote.
Challenge: Add LED indicator for system status.

🎮 Microproject 2.8.2 – Touch intruder detection

Goal: Detect intruder touch when system active.

MicroPython Code:

# Touch intruder detection
# This program detects touch input as intruder alert

import machine, time                          # Import machine and time libraries

tc2 = machine.TouchPad(machine.Pin(2))        # Setup touch sensor on pin 2
system_active = True                          # Assume system is active

print("Touch detection ready")                # Serial start message

while True:                                   # Infinite loop
    if system_active:                         # Only check if system active
        value = tc2.read()                    # Read touch sensor value
        if value < 300:                       # Threshold for touch detection
            print("Intruder detected by touch!") # Serial alert
    time.sleep(0.1)                           # Delay for stability

Reflection: Touch sensor detects intruder when system active.
Challenge: Add buzzer alarm when intruder detected.

🎮 Microproject 2.8.3 – Impact detection

Goal: Detect crash sensor input.

MicroPython Code:

# Impact detection
# This program detects impact using crash sensor

import machine, time                          # Import machine and time libraries

pin5 = machine.Pin(5, machine.Pin.IN)         # Setup crash sensor on pin 5
system_active = True                          # Assume system is active

print("Impact detection ready")               # Serial start message

while True:                                   # Infinite loop
    if system_active:                         # Only check if system active
        if pin5.value() == 1:                 # If crash sensor triggered
            print("Impact detected!")         # Serial alert
    time.sleep(0.1)                           # Delay for stability

Reflection: Crash sensor detects impact events.
Challenge: Add buzzer alarm when impact detected.

🎮 Microproject 2.8.4 – Differentiated alarm by sensor

Goal: Trigger different alarms for touch vs impact.

MicroPython Code:

# Differentiated alarm by sensor
# This program uses buzzer to play different alarms for touch and impact

import machine, time, music                   # Import machine, time, and music libraries

tc2 = machine.TouchPad(machine.Pin(2))        # Touch sensor setup
pin5 = machine.Pin(5, machine.Pin.IN)         # Crash sensor setup
midi = music.MIDI(26)                         # Buzzer setup
system_active = True                          # Assume system is active

print("Differentiated alarm ready")           # Serial start message

while True:                                   # Infinite loop
    if system_active:                         # Only check if system active
        if tc2.read() < 300:                  # Touch detected
            midi.pitch_time(440, 200)         # Play beep for touch
            print("Touch alarm triggered")    # Serial alert
        if pin5.value() == 1:                 # Impact detected
            midi.pitch_time(523, 200)         # Play different beep for impact
            print("Impact alarm triggered")   # Serial alert
    time.sleep(0.1)                           # Delay for stability

Reflection: Different alarms help identify type of intrusion.
Challenge: Add LED ON for touch, OFF for impact.

🎮 Microproject 2.8.5 – Serial event log

Goal: Record all events in serial monitor.

MicroPython Code:

# Serial event log
# This program records all events in serial monitor

import machine, time, music                   # Import machine, time, and music libraries

tc2 = machine.TouchPad(machine.Pin(2))        # Touch sensor setup
pin5 = machine.Pin(5, machine.Pin.IN)         # Crash sensor setup
midi = music.MIDI(26)                         # Buzzer setup
system_active = True                          # Assume system is active

print("Event log ready")                      # Serial start message

while True:                                   # Infinite loop
    if system_active:                         # Only check if system active
        if tc2.read() < 300:                  # Touch detected
            midi.pitch_time(440, 200)         # Play beep
            print("LOG: Touch intrusion detected") # Log event
        if pin5.value() == 1:                 # Impact detected
            midi.pitch_time(523, 200)         # Play beep
            print("LOG: Impact intrusion detected") # Log event
    time.sleep(0.1)                           # Delay for stability

Reflection: Serial monitor now records all intrusion events.
Challenge: Add timestamps to log entries.

✨ Main Project – Basic Security System (continuación y completo)

Goal: Combine all microprojects into one complete security system.

MicroPython Code:

# Project 2.8 – Basic Security System (Main Project)
# This program combines IR remote, touch sensor, crash sensor, and buzzer into a full security system

import machine, time, music, irremote         # Import libraries for pins, time, buzzer, and IR

ir_rx = irremote.NEC_RX(18,8)                 # Setup IR receiver on pin 18
tc2 = machine.TouchPad(machine.Pin(2))        # Setup touch sensor on pin 2
pin5 = machine.Pin(5, machine.Pin.IN)         # Setup crash sensor on pin 5
midi = music.MIDI(26)                         # Setup buzzer on pin 26

system_active = False                         # Start with system OFF

print("Basic Security System ready")          # Print start message to serial monitor

while True:                                   # Infinite loop
    if ir_rx.any():                           # If IR signal received
        code = ir_rx.code[0]                  # Read the first code from buffer
        if code == 0xA90:                     # Example ON button code
            system_active = True              # Activate system
            print("System activated")         # Serial confirmation
        elif code == 0xA91:                   # Example OFF button code
            system_active = False             # Deactivate system
            print("System deactivated")       # Serial confirmation

    if system_active:                         # Only check sensors if system is active
        if tc2.read() < 300:                  # If touch sensor detects intrusion
            midi.pitch_time(440, 200)         # Play buzzer alarm for touch
            print("LOG: Touch intrusion detected") # Log event in serial
        if pin5.value() == 1:                 # If crash sensor detects impact
            midi.pitch_time(523, 200)         # Play buzzer alarm for impact
            print("LOG: Impact intrusion detected") # Log event in serial

    time.sleep(0.1)                           # Small delay for stability

📖 External Explanation

• What it teaches: How to combine IR remote, touch, and crash sensors into a complete security system.
• Why it works: The IR remote activates/deactivates the system, and when active, sensors trigger alarms and log events.
• Key concept: Inputs (IR, touch, crash) control outputs (buzzer, serial log).

✨ Story Time

Imagine your robot as a guardian 🛡️. With the remote, you arm or disarm it. If someone touches it or bumps into it, alarms sound and events are recorded. It’s like having a mini alarm system protecting your robot.

🕵️ Debugging (2 Common Problems)

🐞 Debugging 2.8.A – False alarms

Problem: System triggers alarms even when no intrusion.
Clues: Touch sensor values fluctuate.
Broken code:

if tc2.read() < 600:   # Threshold too high
    print("Intruder detected")

Fixed code:

if tc2.read() < 300:   # Correct threshold
    print("Intruder detected")

Why it works: Lower threshold avoids false triggers.
Avoid next time: Calibrate sensor values before setting threshold.

🐞 Debugging 2.8.B – It does not detect real events

Problem: System ignores actual intrusions.
Clues: Crash sensor wired incorrectly.
Broken code:

pin5 = machine.Pin(5, machine.Pin.OUT)   # Wrong mode

Fixed code:

pin5 = machine.Pin(5, machine.Pin.IN)    # Correct mode

Why it works: Crash sensor must be input, not output.
Avoid next time: Always check sensor wiring and pin mode.

✅ Final Checklist

• IR remote activates/deactivates system.
• Touch sensor detects intruder when active.
• Crash sensor detects impact when active.
• Buzzer plays different alarms for touch vs impact.
• Serial monitor logs all events.

📚 Extras

• 🧠 Student tip: Test thresholds for touch sensor to avoid false alarms.
• 🧑‍🏫 Instructor tip: Encourage students to simulate intrusions and observe system response.
• 📖 Glossary: Touch sensor, crash sensor, IR remote, buzzer, intrusion log.
• 💡 Mini tips:
  • Always calibrate sensors before use.
  • Use IR Configuration project to map button codes.
  • Keep delays short for responsive alarms.