10. Output Devices¶
Global Class¶
This week focuses on how microcontrollers interact with the physical world by driving external devices. Outputs convert digital signals into physical actions such as light, motion, sound, or heat.
Types of Output Devices¶
Common output categories include:
- LEDs and displays
- speakers and audio systems
- motors and actuators
Power and Energy Considerations¶
Unlike input devices, outputs often require significant power.
Key concepts:
- voltage
- current
- power consumption
Incorrect design can lead to:
- overheating
- component damage
- unstable system behavior
Electrical Safety¶
Working with output devices introduces higher power levels.
Important thresholds:
- ~1 mA → generally safe
- ~10 mA → muscle contraction
- ~100 mA → dangerous (fibrillation risk)
Additional risks:
- stored energy in capacitors
- inductive voltage spikes (flyback)
Safe practices:
- clear wiring
- controlled testing environment
- avoid working alone
- verify circuits before powering
Power Supply Strategies¶
Different approaches to powering systems:
- bench power supplies (controlled testing)
- USB power delivery (flexible and accessible)
- battery systems (LiPo)
- DC-DC converters
Modern USB-C systems allow dynamic voltage and current negotiation.
Power Measurement¶
Understanding consumption is essential:
- measure voltage and current
- calculate power usage
- ensure components operate within limits
Tools:
- multimeter
- inline current measurement
Output Control¶
Microcontrollers typically cannot drive high-power devices directly.
Instead, they use:
- transistors
- drivers
- relays or solid-state relays (SSR)
This creates a safe interface between low-voltage control and high-power systems.
Local Class¶
Output Devices Introduction¶
This session focused on how microcontrollers drive physical systems through output devices. The main idea is that outputs translate digital signals into real-world effects such as light, motion, and heat.
Dani demonstrated LED control using programmable lighting, showing how digital signals can generate dynamic visual behavior.
Light — Addressable LEDs¶
We explored NeoPixel (addressable LED) systems.
Key concepts:
- each LED has an individual address
- controlled through a single data line
- requires specific timing and libraries (Adafruit / Arduino IDE)
This introduces the idea of complex outputs controlled through simple interfaces.
Motors and Motion¶
Different motor types were introduced, focusing on their behavior and control:
- DC motors → simple, continuous rotation
- stepper motors → precise position control, lower torque
- BLDC motors → efficient, high-performance systems
- servo motors → controlled angular position using PWM signal (typically limited range)
Key parameters:
- torque
- speed
- control method
A visual explanation of motor structure helped understand internal operation.
Switching High Power¶
To control real-world devices, microcontrollers require switching components:
- MOSFET → fast electronic switch (transistor-based)
- relay / SSR → electrically isolated switching
Microcontrollers do not drive power directly — they control switching devices.
Control Logic — PID¶
A hardware demonstration of a PID controller showed how systems can regulate behavior dynamically.
Concepts introduced:
- proportional → reacts to current error
- integral → accumulates past error
- derivative → predicts future behavior
This allows systems to stabilize outputs such as:
- motor position
- temperature
- speed
Relevance to ASFALT¶
This session directly defines the ASFALT actuation system:
- SSR / MOSFET → control heating element
- LEDs → system feedback and status
- PID → future temperature regulation
Together, these elements define how ASFALT:
- delivers heat
- controls energy
- responds to sensor input
Weekly Assignment¶
Output Devices — ASFALT-Oriented Prototype¶
This week focuses on controlling an output device that represents the ASFALT heating system, without using high-voltage components.
Instead of directly driving a 220V heater, a low-voltage proxy system was developed to simulate heat control behavior.
Individual Assignment¶
Goal¶
Develop a minimal output system that mimics the behavior of a heating element using safe, low-power components.
Output Strategy¶
The heating system was abstracted into a controllable energy output:
microcontroller → switching → energy delivery
To simulate this, a PWM-controlled load was used.
Hardware Setup¶
The system consists of:
- microcontroller board (from previous weeks)
- N-channel MOSFET (switching element)
- resistive load (LED / power resistor)
- external low-voltage power supply
Connections:
- GPIO → MOSFET gate
- MOSFET drain → load
- load → VCC
- MOSFET source → GND
This creates a safe switching circuit equivalent to a heater control stage.
Control Method¶
The output is controlled using PWM (Pulse Width Modulation).
This allows:
- variable power delivery
- simulation of heat intensity levels
Control mapping:
- 0% duty cycle → OFF
- 100% duty cycle → full power
- intermediate values → partial power
Code Logic¶
The program:
- initializes PWM output
- sets duty cycle based on input value
- updates output continuously
Basic flow:
- define output pin
- configure PWM
- write duty cycle
Observations¶
- smooth control of output intensity
- stable switching behavior through MOSFET
- clear relationship between PWM value and output power
Problems and Fixes¶
-
incorrect MOSFET wiring
→ verified gate, drain, source configuration -
weak output response
→ ensured proper power supply and load selection
Result¶
The system successfully:
- controls a resistive load using PWM
- simulates variable heat output
- demonstrates safe switching architecture
Reflection¶
This prototype abstracts the heater into a controllable energy system.
Key insight:
heat control is fundamentally power modulation
Relevance to ASFALT¶
This experiment directly represents the ASFALT heating control system:
- MOSFET → equivalent to SSR (low vs high voltage)
- PWM → power modulation strategy
- load → simplified heater model
This establishes the final control chain:
sensor → microcontroller → switching → heat output
The next step is replacing the low-voltage stage with:
- SSR
- real heating element
without changing the control logic.