NCEA L1 Digital Tech: Electronic environments and embedded systems

Electronic environments and embedded systems tests how inputs, processing and outputs combine in a physical device. You need to read simple circuit diagrams, identify components, and trace a control program.

Core rules and concepts

• An embedded system is a computer dedicated to one task inside a larger product; it usually has a microcontroller with CPU, memory and GPIO pins.
• Inputs include switches, LDRs and temperature sensors. Outputs include LEDs, buzzers and motors. A motor is often driven through a transistor or relay because a GPIO pin cannot supply enough current.
• Digital pins read HIGH or LOW; analog pins read a range. A pull-up or pull-down resistor stops an input from "floating".
• Programs follow a loop: read inputs, make a decision, set outputs, repeat. Use delay only when blocking is acceptable.

Worked example

A night light switches an LED on when an LDR reading falls below 300.

loop forever:
  light = read analog pin A0
  if light < 300:
    set pin 9 HIGH
  else:
    set pin 9 LOW

Reasoning: A0 is an input; pin 9 is an output set with pinMode(9, OUTPUT). The threshold converts a continuous reading into a Boolean decision. Add hysteresis (on below 280, off above 320) to stop flicker near the threshold.

Traps

• Forgetting to set pin modes.
• Wiring an LED without a series resistor.
• Assuming an active-low button reads HIGH when pressed.
• Using a blocking delay that makes the device miss button presses.
• Confusing a sensor (input) with an actuator (output).