Tutorial 2 prep

It is all about understanding how hardware and software interact to solve real-world problems. This sheet focuses on the transition from simple circuits to "intelligent" systems.

Here is a breakdown of the concepts and suggested answers to help you lead the discussion or answer questions in class.

The Electric Water Heater Controller
This example highlights the basic "Sense-Think-Act" cycle of an embedded system.

Inputs: The Thermometers (likely thermistors or RTDs) and the Temperature Setpoint dial (a potentiometer or digital buttons).
Outputs: The Heating Elements (controlled via relays or triacs) and potentially a status LED or digital display showing current temperature.
Safety Features:
- Over-temperature Cutoff: A software limit that disables the heater if $T > T_{m a x}$ , backed by a Hardware Thermal Fuse (bimetallic switch) for redundancy if software fails.
  - Dry-Fire Protection: Software can detect a rapid temperature spike without a corresponding increase in thermal mass (water), signaling the heater to stop. Hardware would require a Water Level Sensor.
Software Features:
- No Extra Hardware: A self-diagnostic routine that checks if the temperature rises when the heater is "on"; if not, it signals a "heater failed" error code.
  - Energy Saving (with Time of Day): Scheduled Heating (only heating during off-peak electricity hours) or Usage Prediction (learning when you usually shower to pre-heat water just in time).
- IoT Feature: Remote monitoring and control via a mobile app, or receiving firmware updates to improve the heating algorithm.

Flashlight "Auto-Off" Alternatives
The goal here is to think about timing without a microcontroller (MCU).

Approach	Implementation Method
Electronic	A 555 Timer circuit in monostable mode or a simple RC (Resistor-Capacitor) circuit where the discharging capacitor keeps a transistor gate open for 3 minutes.
Mechanical	A spring-wound timer (like a kitchen timer) that physically breaks the circuit after a set duration of rotation.
Pneumatic	A leaky piston/bellows system. Turning the light on compresses air; a small orifice allows air to leak out slowly over 3 minutes until the piston moves far enough to toggle a switch.

The "Smart" Flashlight
Adding an embedded computer allows for functionality that is hard to achieve with discrete components.

Signaling Modes: Programmed SOS or strobe patterns for emergencies.
Dimming/Brightness Control: Using Pulse Width Modulation (PWM) to provide multiple brightness levels without wasting energy as heat.
Battery Management: Accurate state-of-charge (SoC) estimation and low-battery protection to prevent cell damage.

Embedded Systems in Automobiles
Modern cars are essentially "computers on wheels" for safety, efficiency, and comfort.

Engine Control Unit (ECU): Optimizes fuel injection and ignition timing. Benefit: Higher fuel efficiency and lower emissions.
Anti-lock Braking System (ABS): Prevents wheel lock-up during hard braking. Benefit: Prevents skidding and maintains steering control.
Airbag Control Unit: Processes accelerometer data to deploy airbags in milliseconds. Benefit: Critical life-saving safety.
Electronic Stability Control (ESC): Applies individual brakes to help steer the vehicle during loss of traction. Benefit: Reduces rollover and spin-out risks.
Adaptive Cruise Control: Uses radar/lidar to maintain distance from the car ahead. Benefit: Reduces driver fatigue and improves traffic flow.

Identifying Other Devices
Look for devices that require decision-making or user interfaces.

Microwave Oven: Inputs (keypad, door sensor), Outputs (magnetron, turntable, buzzer). It improves the device by allowing precise timing and preset cooking modes.
Digital Camera: Inputs (shutter button, light sensor), Outputs (lens motor, LCD screen). It allows for image processing, autofocus, and digital storage.
Washing Machine: Inputs (load weight sensor, dial), Outputs (motor, water valves). It optimizes water usage and cycle times based on the load.

Bonus: How does ABS work?