11. Output devices¶

Assignment

Group assignment:

Measure the power consumption of an output device.
Document your work on the group work page and reflect on your individual page what you learned.

Individual assignment:

Add an output device to a microcontroller board you’ve designed and program it to do something.

Learning outcomes

Demonstrate workflows used in controlling an output device(s) with MCU board you have designed.

Have you answered these questions?

Linked to the group assignment page.
Documented how you determined power consumption of an output device with your group.
Documented what you learned from interfacing output device(s) to microcontroller and controlling the device(s).
Linked to the board you made in a previous assignment or documented your design and fabrication process if you made a new board.
Explained the programming process/es you used.
Explained any problems you encountered and how you fixed them.
Included original source code and any new design files.
Included a ‘hero shot’ of your board.

Basic Definition of Output Devices¶

My two favority resources

Learning about Electronics for studying Electronic Components, Produccts, Concepts, Reference Tools.
Random Nerd Tutorials provides useful tutorial resources to build electronics projects.

Electrical Safety

Definition: Electrical safety encompasses the principles, design practices, and preventive measures aimed at protecting humans, equipment, and systems from the harmful effects of electrical currents and voltages. It addresses current thresholds for physiological effects, safe component usage, circuit protection, and design strategies to prevent electric shock, fire, or damage due to improper polarity, overvoltage, or component failure.

Key elements include:

Human Current Thresholds:

~1 mA: generally safe, perceptible current ~10 mA: may cause involuntary muscular contraction (let-go threshold) ~100 mA: risk of ventricular fibrillation and potential fatality (Ref: IEEE Std 602, IEC 60479-1)

Body Resistance:

External (dry skin): in the megaohm (MΩ) range
Internal (wet/tissue): drops to kiloohms (kΩ) (Ref: IEC 60479-1, “Effects of current on human beings and livestock”)

Dielectric Breakdown:

Typical dielectric strength of air is ~1 kV/mm; insulation materials must exceed this to avoid arcing. (Ref: IEEE Std 4, ANSI/ASTM D149)

Component and Circuit Protection Strategies:

Supply capacitors must have proper voltage ratings and discharge paths.
Inductive flyback protection involves using flyback diodes or snubber circuits across inductive loads to prevent voltage spikes.
Polarity protection: achieved via diodes or P-channel MOSFETs to block reverse current.
Level shifting (e.g., for interfacing 3.3V and 5V logic) uses MOSFET-based bidirectional circuits.
Connector polarization and mechanical orientation prevent miswiring.
Overcurrent, overvoltage, and thermal protection is implemented using fuses, TVS diodes, PTC resettable fuses, and other active protection elements. (Ref: Horowitz & Hill, The Art of Electronics, 3rd ed.; UL 60950, IPC standards, Texas Instruments Protection Design Guides)

Power Systems in Electronics

Definition:Power systems in electronics refer to the methods, components, and design principles used to generate, manage, distribute, and regulate electrical energy within circuits and electronic devices. This includes both energy sources and conditioning elements to ensure safe, reliable, and efficient power delivery across varying applications.

Wire Gauge (AWG - American Wire Gauge)

Wire gauge determines the current-carrying capacity of conductors. Smaller gauge numbers correspond to thicker wires, allowing higher current flow with less resistance and voltage drop.
Critical for preventing overheating or fire due to excessive current. Reference: NEC (National Electrical Code), IPC-2221, UL 758

USB Power Systems

USB (Universal Serial Bus) standards have evolved to deliver both data and power.
USB Charger: Delivers 5V (standard) or higher under USB-PD (Power Delivery), up to 100W.
USB Hub: Expands USB ports; may include its own power supply.
USB Battery Pack: Portable storage for DC power, typically using Li-ion or LiPo batteries.
USB Module: Embedded modules for USB-based communication and power supply.
USB Power Meter: Used to measure current, voltage, and power flow in USB-powered devices. Reference: USB Battery Charging Specification Rev 1.2, USB Power Delivery Specification Rev 3.1

Power Supplies

Bench Power Supply: Laboratory tool providing adjustable, regulated voltages; used for prototyping.
Switching Power Supply: Efficient, uses high-frequency switching to regulate output voltage (e.g., buck, boost converters).
Linear Power Supply: Simpler, uses linear regulation; lower noise but less efficient.
Regulated Power Supply: Maintains constant output regardless of input fluctuation or load. Reference: Texas Instruments Power Supply Design Guide, Horowitz & Hill, IEC 61204

Supercapacitor (Ultracapacitor) A high-capacity capacitor used for short-term energy storage with rapid charge/discharge cycles. Often used for backup power or energy buffering. Reference: Maxwell Technologies Application Notes, IEEE Transactions on Power Electronics

Lithium Polymer (LiPo) Batteries Rechargeable batteries with high energy density and flexible form factor, widely used in mobile electronics, drones, and robotics.

Requires precise Battery Charge Controllers for safe charging/discharging.
Battery Storage involves considerations of temperature, charge level, and safety enclosure. Reference: JEITA standard RC-5237, IEEE 1725 Standard for Rechargeable Batteries

Wireless Power Refers to energy transfer without physical connectors, typically using electromagnetic fields (e.g., inductive charging).

Common in mobile devices, medical implants, and electric vehicles. Reference: Qi Wireless Power Consortium Standard, IEEE 802.11bb for light-based wireless

Current Measurement

Definition: Current measurement in electrical and electronic systems refers to the process of determining the amount of electric charge flow (current) through a conductor. Techniques vary in terms of invasiveness, accuracy, and isolation, and are fundamental to power management, protection systems, and device diagnostics.

Key Methods and Concepts In-line Meter An in-line current meter measures current by being physically inserted into the current path.

Measures real-time current directly (often both voltage and current).
Common in USB power testing and battery diagnostics. Reference: Keysight AN 3461: Current Measurement Techniques

Supply Regulation In regulated power supplies, current sensing is integrated for maintaining output stability, enabling overcurrent protection, and supporting constant-current modes.

Linear and switching regulators use feedback loops that may include current sense circuits. Reference: Texas Instruments, Power Supply Design Guide

Sense Resistor (Shunt Resistor) A precision low-ohmic resistor placed in series with the load to develop a small voltage proportional to current:

𝑉 sense = 𝐼⋅𝑅 sense

Requires amplification due to low voltage levels.
Offers high precision, commonly used in DC circuits. Reference: Analog Devices, “Current Sensing Solutions Guide”

Magnetic Field Sensing (Hall Effect) Measures current by detecting the magnetic field generated by the flow of electrons through a conductor.

Provides galvanic isolation from the measured circuit.
Suitable for AC and DC currents. Reference: Allegro Microsystems Application Notes on Hall Sensors

Inductance-Based Sensing Used in non-contact AC current measurement, especially with:

Current transformers for high-current AC applications.
Rogowski coils for measuring rapidly changing currents. These methods rely on Faraday’s Law of Induction: 𝑉 = − 𝐿 𝑑𝐼/𝑑𝑡

Reference: IEEE Transactions on Instrumentation and Measurement

LEDs and RGB LEDs

Definition: LEDs (Light Emitting Diodes) are semiconductor diodes that emit light when forward-biased. RGB LEDs combine three diodes (Red, Green, Blue) in a single package, enabling full-color generation through intensity mixing. Efficient control of LEDs involves understanding current regulation, electrical characteristics, and switching components such as MOSFETs or BJTs to handle larger loads or digital control.

LED Current Limiting

To prevent damage due to excessive current, a current-limiting resistor is used:

𝑅 = (𝑉supply - 𝑉fwd)/𝐼

Forward voltage (diode drop) varies by color:

Red ≈ 1.8–2.2V, Green/Blue ≈ 2.8–3.3V
Typical current: 10–20 mA for standard LEDs Reference: Horowitz & Hill, “The Art of Electronics”

RGB LEDs RGB LEDs consist of three LEDs in a single package. Variants:

Common Anode / Common Cathode
Individually addressable pixels (e.g., WS2812) include integrated ICs for serial control.

Control Considerations:

Wires & Topology: Daisy-chained digital inputs (for pixel LEDs) or parallel GPIO wiring (for discrete RGB).
Power: High power draw for arrays; proper decoupling and voltage regulation required. Reference: Adafruit Neopixel Guide; IEEE Spectrum on Digital Light Control

Series and Parallel LED Configurations

Series: Same current, voltages add up
Parallel: Same voltage, currents add up
Requires balancing resistors or constant-current drivers to ensure equal brightness.

MOSFETs in LED Control MOSFETs are widely used to switch high-current LED circuits.

Types: - N-channel: Typically used on the low side (drain to load) - P-channel: Used on high side, but more complex gate driving - Triple N (N, P, N): Often used in gate driver circuits or to implement level shifting

Key Concepts: - Gate Resistor: Slows down switching to reduce EMI and ringing - Floating Gate: Must be actively driven to prevent unintended switching - R_DS(on): On-resistance affects heat dissipation; lower is better

Power Dissipation:

𝑃 = 𝐼‘2* 𝑅 DS(on) + Switching Losses

Switching Losses Switching Losses: Occur during transitions; increase with frequency Reference: Infineon Application Note: Driving Power MOSFETs

Alternatives to MOSFETs - BJT (Bipolar Junction Transistor): Current-controlled; higher gain, but slower - BiCMOS: Combines BJT analog performance with CMOS logic - IGBT (Insulated Gate Bipolar Transistor): Combines MOS gate with BJT output; used in very high-power applications Reference: IEEE Transactions on Power Electronics

Thermal Runaway A risk in LEDs and power transistors where increased temperature leads to increased current, further raising temperature—a feedback loop.

Prevented by thermal design, heat sinking, derating, and constant-current sources. Reference: JEDEC JESD51 Thermal Guidelines

Display Technologies in Embedded Systems

Definition: Display technologies in embedded and digital systems refer to electronic visual output devices that convert electrical signals into human-readable graphical or textual information. Each display type offers specific trade-offs in terms of power consumption, contrast, response time, and suitability for outdoor or battery-operated applications.

LCD (Liquid Crystal Display)

Operates by modulating light through liquid crystal layers between polarizing filters.
Requires backlighting (commonly LED-based).
Types: Segmented LCD: Fixed characters/symbols (e.g., digital watches) Dot-matrix LCD: Flexible graphics (e.g., 128x64)
Advantages: Low power, inexpensive
Limitations: Narrow viewing angle, lower contrast Use Cases: Meters, calculators, low-power devices Reference: IEEE Microelectronics Journal; HD44780 LCD Controller Datasheet

OLED (Organic Light Emitting Diode)

Each pixel emits its own light using organic compounds.
Does not require a backlight, enabling ultra-thin and flexible displays.
Advantages: High contrast, true blacks, wide viewing angle
Limitations: Shorter lifespan, especially blue pixels; potential burn-in Use Cases: Smartwatches, mobile devices, small graphic displays Reference: SID Journal of Display Technology

TFT (Thin Film Transistor LCD)

A type of active-matrix LCD where each pixel is controlled by a dedicated transistor.
Full color, fast refresh rates, good contrast compared to traditional LCDs.
Common interfaces: SPI, parallel (8080/6800), LVDS
Advantages: Suitable for high-resolution GUIs and video playback
Limitations: Higher power than passive LCDs; sunlight readability varies Use Cases: Touchscreens, HMI panels, handheld consoles Reference: NXP and STMicroelectronics TFT Display Interface Guides

E Ink (Electrophoretic Ink) Modules

Uses charged microcapsules to reflect light and display content like ink on paper.
Bistable: retains image without power
Advantages: Extremely low power, sunlight-readable, wide viewing angle
Limitations: Slow refresh rates, limited color support Use Cases: eReaders, shelf labels, low-power signage Reference: E Ink Corporation White Papers; IEEE Transactions on Displays

Video Signal Standards and Microcontroller-Based Video Output

Definition: Video signaling systems are standardized methods for transmitting analog or digital video data from a source to a display. These standards define resolution, frame rate, color encoding, synchronization, and electrical properties such as impedance. In embedded systems, lightweight implementations like SPI-based TVout or thin client graphics are used to generate simple video outputs from constrained microcontrollers.

Analog Video Standards RS-170

Monochrome video signal standard (U.S. origin, 1941)
Basis for later color standards like NTSC
525 lines, 30 fps, black and white Reference: EIA RS-170 Standard

NTSC (National Television System Committee)

North American color video standard
525 lines, 29.97 fps, interlaced
Composite video with color subcarrier at 3.58 MHz Reference: SMPTE Standards; FCC NTSC Guide

PAL (Phase Alternating Line)

European color standard
625 lines, 25 fps, improved color stability
4.43 MHz subcarrier Reference: ITU-R BT.470-6

SECAM (Séquentiel Couleur à Mémoire)

French/Russian color encoding
Sequential color transmission, 625 lines, 25 fps
Incompatible with NTSC/PAL hardware Reference: Union Internationale des Télécommunications (ITU)

VGA (Video Graphics Array)

Analog RGB with sync on separate lines
Common resolution: 640×480 @ 60 Hz
Used with PC monitors Reference: VESA Display Standards

75 Ohm Impedance Matching

Standard for composite video output and analog video signals
Prevents signal reflections and ensures proper transmission line behavior
Video sources typically have 75-ohm series resistors; cables and terminations must match Reference: Tektronix Oscilloscope Guide on Video Signal Measurement

Microcontroller-Based Video Output SPI TVout - Technique for generating composite video using SPI and digital I/O pins - Outputs monochrome or low-color video using precise timing and waveform generation - Examples: Arduino TVout library, ESP32 SPI video out

Advantages:

No video card required
Can output to analog TVs using RCA connectors

Limitations:

Limited resolution and color depth
Tight CPU timing constraints

Reference:

Nick Gammon’s AVR Video Signal Generation
Fab Academy Projects using TVout libraries

Thinner Client Video

Refers to minimalist clients (often microcontrollers) rendering GUI/video with minimal memory, offloading complex tasks to a server or host (e.g., over UART, SPI, or I²C).
Common in IoT displays, embedded HMI panels, or dumb terminals. Example Use: Receiving framebuffer or draw commands via SPI/UART from a Raspberry Pi or host computer. Reference: Microchip Graphics Library, LVGL Documentation

Electric Actuators: Types, Control, and Applications

🔹 1. Solenoids Solenoids are electromechanical devices that convert electrical energy into linear motion via an electromagnetic field. When current passes through a coil, it generates a magnetic field that actuates a ferromagnetic plunger or armature.

  Types:

    Pull-type: Common in door locks, vending machines.
    Push-type: Less common, often used in pin eject mechanisms.
    Control: On/off via transistor/MOSFET switch; no positional feedback.
    Duty Cycle: Must consider heat dissipation due to continuous current draw.

🔹 2. Servo Motors Servo motors are geared DC motors with integrated control electronics and feedback (usually via potentiometers) that enable precise angular positioning.

    Control Signal: PWM signal with 50 Hz frequency:

      1.0 ms pulse ≈ 0°

      1.5 ms pulse ≈ 90°

      2.0 ms pulse ≈ 180°

    Types:

      Standard (positional): Rotates up to ~180° with feedback.

      Continuous rotation: Interprets PWM as speed/direction (not angle).

      Applications: Robotics joints, RC vehicles, pan-tilt mechanisms.

🔹 3. Brushless DC Motors (BLDC) BLDC motors offer high efficiency, power density, and reliability by replacing mechanical commutators with electronic switching.

    Construction:
    Inrunner: Rotor inside, stator outside (high-speed, low torque).

    Outrunner: Rotor outside (used in drones, higher torque).

    Pancake/Gimbal/Fan types: Specialized form factors for different torque/inertia needs.

    Electrical Characteristics:
    Kv rating (RPM/V): Higher Kv = higher speed, lower torque.

    Phase commutation: Typically 6 steps per revolution in trapezoidal drives.

    Back EMF (BEMF): Induced voltage used for sensorless control.

    Control Modes:
    Open-loop: Simple 6-step commutation, no feedback (used in sensorless designs).

    Closed-loop: Hall effect sensors or BEMF sensing to adjust drive signals.

    Drive waveform: Trapezoidal or sinusoidal commutation.

    ESC – Electronic Speed Controller:
    An ESC manages power delivery and switching logic.

    Triple Half-Bridge Architecture: 3-phase inverter topology (e.g., A4949 driver).

    Firmware: Typically runs real-time control (e.g., BLHeli, SimonK).

    Inputs:

    PWM servo signals (1–2 ms)

    Battery power (LiPo typically)

    Functions:

    Motor initialization (e.g., slow ramp-up)

    Calibration (max/min throttle)

    Protection: overcurrent, thermal

    Use Cases:
    ~1 A (cooling fans)

    ~10 A (drones)

    ~100 A (electric skateboards)

    ~1000 A (EVs, e.g., Tesla drive motors)

🔹 4. Stepper Motors Stepper motors divide rotation into discrete steps, offering precise control without feedback in open-loop systems.

    Types:
    Permanent Magnet (PM)

    Variable Reluctance (VR)

    Hybrid: Most common, 1.8° per step (200 steps/rev)

    Stepping Modes:
    Full step: 1.8° per pulse

    Half step: 0.9°, alternating single and double coil energizing

    Microstepping: Fine control via sinusoidal current profiles

    Driver Control:
    Step/Dir Interface: Common method using digital pulses and direction signal.

    DRV8428: Advanced driver with configurable current and microstepping.

    H-Bridge: Required for bipolar steppers.

    Wire Identification:
    Use a multimeter to find coil pairs (low resistance between two wires).

    Control Considerations:
    Current limiting is essential to prevent overheating.

    Dwell time (pulse duration) affects step reliability and torque.

    Open-loop vs. closed-loop steppers (with encoder feedback for correction).

    Advanced Concepts:
    Electro-permanent actuation: Uses magnetic latching to hold position without continuous current.

    Electrostatic actuators: Niche use; high voltage, low current; micro-mechatronics.

    📚 References
    Hughes, A. (2016). Electric Motors and Drives. Elsevier.

    TI DRV8428 and DRV8847 Datasheets – Texas Instruments

    Allegro A4949 BLDC Motor Controller Datasheet – Allegro Microsystems

    Ulrich, K. T., & Eppinger, S. D. (2020). Product Design and Development.

    Petruzzelli, V. (2012). Mechatronics and Automatic Control Systems. Springer.

    IEEE 1149 and ISO 26262 (for ESCs and motor safety protocols)

Experiments with Output Devices¶

Experiment with Henk¶

We had practical lesson from the Waag Futurelab and Henk made a presentation on the output devices by using

Ervin Kooi’s presentation on output devices

Then the Waag Futurelab demonstrated several experiments and one of interwesting experiments was the experiment with parrellel connected LEDs, which allowed us to understand OhM Law in practice, in particulalrly, as electricity flows through each LED it takes different values where as the voltage remains in stable value.

Experiment with Stepper-motor¶

Experiment with Stepper-motor

Code:

#define STEP_PIN 9
#define DIR_PIN 8

void setup() {
pinMode(STEP_PIN, OUTPUT);
pinMode(DIR_PIN, OUTPUT);
digitalWrite(DIR_PIN, HIGH); 
}

void loop() {
digitalWrite(STEP_PIN, HIGH);
delayMicroseconds(500);
digitalWrite(STEP_PIN, LOW);
delayMicroseconds(500);
}

Experiment with Speaker¶

Experiment with Speaker

Code:

const int SPEAKER=9;
int notes[] = {
1318, 1318, 1318, 1046, 1318, 1568, 784,
1046, 784, 659, 880, 987, 932, 880, 784,
1318, 1568, 1750, 1396, 1568, 1318, 1046, 1174, 987,
1046, 784, 659, 880, 987, 932, 880,
784, 1318, 1568, 1750, 1396, 1568, 1318, 1046, 1174, 987,
1568, 1480, 1396, 1244, 1318, 830, 880, 1046, 880, 1046, 1174,
0, 1568, 1480, 1396, 1244, 1318, 2093, 2093, 2093,
1568, 1480, 1396, 1244, 1318, 830, 880, 1046, 880, 1046, 1174, 1244, 1174, 1046,
};
int times[] = {
150, 300, 150, 150, 300, 600, 600,
450, 150, 300, 300, 150, 150, 300, 210,
210, 150, 300, 150, 150, 300, 150, 150, 450,
450, 150, 300, 300, 150, 150, 300,
210, 210, 150, 300, 150, 150, 300, 150, 150, 450,
150, 150, 150, 300, 150, 150, 150, 150, 150, 150, 150,
0, 150, 150, 150, 300, 150, 300, 150, 600,
150, 150, 150, 300, 150, 150, 150, 150, 150, 150, 150, 300, 450, 600,
};
int delays[] = {
150, 300, 300, 150, 300, 600, 600,
450, 450, 450, 300, 300, 150, 300, 210,
210, 150, 300, 150, 300, 300, 150, 150, 450,
450, 450, 450, 300, 300, 150, 300,
210, 210, 150, 300, 150, 300, 300, 150, 150, 600,
150, 150, 150, 300, 300, 150, 150, 300, 150, 150, 150,
300, 150, 150, 150, 300, 300, 300, 150, 600,
150, 150, 150, 300, 300, 150, 150, 300, 150, 150, 450, 450, 450, 1200,
};
void setup(){
for (int i = 0; i < 75; i++){
tone(SPEAKER, notes[i], times[i]);
delay(delays[i]);
}
noTone(SPEAKER);
}
void loop(){} code speaker

Experiment with LCD-Display¶

Experiment with LCD-Display*

Code:

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Устанавливаем адрес LCD (обычно 0x27 или 0x3F)
LiquidCrystal_I2C lcd(0x27, 16, 2);  // 16 символов, 2 строки

void setup() {
lcd.init();              
lcd.backlight();

lcd.setCursor(0, 0);     
lcd.print("Hello, world!");

delay(2000);

lcd.clear();             
lcd.setCursor(0, 0);     
lcd.print("Fab Academy 2025");
}

void loop() {

}

Experiment with Servo-motor¶

Experiment with Servo-motor*

Code:

#include <Servo.h>
Servo myServo;
void setup() {
myServo.attach(9);
}

void loop() {
for (int angle = 0; angle <= 180; angle++) {
myServo.write(angle);
delay(15);
}

delay(500);
for (int angle = 180; angle >= 0; angle--) {
myServo.write(angle);
delay(15);
}

delay(500);
} code for servo motor