1. Introduction to
microcontrollers.
presented by
Michael Parks, PE
last revision: 24 April 2010

2. what is a
microcontroller?
A tiny computer that is programmable to run one
program, typically in a continuous manner.
Serves as a bridge between the physical world and
the computer world.
Interacts with the “real world” through transducers
such as sensors, actuators, motors, lights, etc.
4 Functions: Input, Process, Output, Communicate
Abbreviated MCU, uC, μC
2

3. what can it do?
In a nutshell, anything you want it do.
a. Two-way interaction with the real-world
b. Hardware and software needed for your design
Some examples I have done:
a. RFID controlled lighting
b. Motion controlled lighting
c. Range detector
d. Laser light game
Input from Output to
Process data via Real-World via
Real-Word
software running Transducers
via Transducers (Actuators,
on MCU hardware
(Sensors) Indicators)
3

4. choosing the right
microcontroller.
Development environment usability
Analog input
Number of digital I/O pins
Speed of execution
Price
Amount of memory
Power
Complexity level based on knowledge and project goals
a. High-Level: Teleo System, I-Cubed, Lego Mindstorms
b. Medium-level: Parallax BASIC Stamp, Arduino
c. Low-level: PIC chips, SX chips, Atmel (AVR) chips
4

5. the Arduino.
Open Source Hardware running the open source
programming language Wiring.
Can interact with a PC through many languages,
most popular is Processing.
5

6. anatomy of a
microcontroller.
UART DIGITAL I/O
INTERRUPT
CPU
CONTROLLER
INTERNAL PULSE WIDTH
TIMERS MODULATION
DATA MEMORY
A/D
PROGRAM CONVERTER
MEMORY
6

7. anatomy of a
microcontroller.
UART DIGITAL I/O
INTERRUPT
CPU
CONTROLLER
INTERNAL PULSE WIDTH
TIMERS MODULATION
DATA MEMORY
A/D
PROGRAM CONVERTER
MEMORY
6

8. anatomy of a
microcontroller.
UART DIGITAL I/O
INTERRUPT
CPU
CONTROLLER
INTERNAL PULSE WIDTH
TIMERS MODULATION
DATA MEMORY
A/D
PROGRAM CONVERTER
MEMORY
6

9. anatomy of a
microcontroller.
UART DIGITAL I/O
INTERRUPT
CPU
CONTROLLER
INTERNAL PULSE WIDTH
TIMERS MODULATION
DATA MEMORY
A/D
PROGRAM CONVERTER
MEMORY
6

10. anatomy of a
microcontroller.
UART DIGITAL I/O
INTERRUPT
CPU
CONTROLLER
INTERNAL PULSE WIDTH
TIMERS MODULATION
DATA MEMORY
A/D
PROGRAM CONVERTER
MEMORY
6

11. microcontroller guts.
7

12. microcontroller guts.
Central Processing
Unit (CPU):
CPU does all the
arithmetic and logic
operations.
It controls the flow of
execution of
instructions.
7

13. microcontroller guts.
RANDOM ACCESS
MEMORY (RAM):
RAM holds the set
of instructions
(program), i.e. being
executed by the
CPU.
It holds important
data required by the
program.
It holds some
important data
structures like
ʻstackʼ.
It is volatile.
7

14. microcontroller guts.
FLASH MEMORY:
Flash memory is
basically EEPROM.
It holds the program
written by the user.
The program can be
erased or written
here many times.
WATCHDOG:
Circuitry to prevent
behaviors that would
have negative
impacts to
microcontroller.
7

15. microcontroller guts.
I/O PORTS:
Each port is made
up of n-pins ( mostly
8 pins).
Each pin can be
configured as either
input pin or output.
If a pin is input pin, it
accepts data from
the device it is
connected to.
If a pin is output pin,
it sends the data to
the device it is
connected to.
7

16. microcontroller guts.
ANALOG-TO-DIGITAL
CONVERTER (DAC):
Most of the real world
signals are analog in
nature.
But a microcontroller is
a digital device, thus it
cannot process analog
signals.
ADC digitizes an analog
signal and gives it to the
microcontroller for
further processing.
7

17. microcontroller guts.
TIMERS:
In many
applications, time
keeping is a must.
Microcontrollers
have timers to
measure time.
SERIAL PORT:
Microcontrollers can
speak to computers
or other digital
equipment via a
serial port.
7

18. Arduino “Duemilanove”
specs.
Built around the ATmega168 microcontroller
14 digital I/O pins (6 provide PWM output)
6 analog inputs (ADC provides quantization)
5 V DC, 40 mA per I/O pin
16 KB of flash memory
1 KB of SRAM
512 bytes of EEPROM
16 MHz clock speed
2 interrupt pins
Supports SPI, I2C, UART 5V TTL serial
8

19. A look at the software side.
9

20. computer science 101.
DATA TYPES
a. Variables (local and global)
i. Numbers: integer, long, float , double
ii. Digital: bit, byte, word
iii. Logic: Boolean
iv. Array
v. Text: char, string
b. Signed versus unsigned
c. Static variables and Constants
d. Keywords or reserved words
e. Converting between data types
f. Structures (C user defined data type)
CONTROL STRUCTURES
a. Operators: arithmetic, comparison, boolean, bitwise, compound
b. if...then...else (conditional statements)
c. Loops
i. main or event loop (infinite loop)
ii. while
iii. do..while
iv. for
v. continue, break, return
d. Recursion
e. Switch case
f. Functions (math and trig) / procedures / subroutine / commands
10

21. computer science 201.
OTHER CONCEPTS
a. Comments
b. Libraries (#include)
c. Flags
d. Pointers
e. Interrupts
f. Random number generator
PROGRAMMING PARADIGMS
a. Syntax (proper combination of words) versus semantics (meaning of those words)
b. Object-oriented programming versus sequential
- class, objects, inheritance, polymorphism, virtual functions
c. Psuedocode before you code
d. Rapid Development and SCRUM
e. Types of Testing: Black Box, White Box, Unit, Integration, Regression, System,
Usability, Acceptance, Alpha, Beta, Security, Stress, Compatibility.
MICROCONTROLLER SPECIFIC FUNCTIONS
a. Digital I/O
b. Analog I/O
c. Advanced I/O: tone, pulses
d. Time
e. Serial Communications
11

22. debugging tips.
writing software is an iterative process.
a. code, verify, debug, compile, upload, reset, and run.
b. Results of a run used to inform next coding cycle.
c. 1/10th of time is coding, 9/10th of time is debugging
keep the program small.
a. add new functionality in small increments.
b. key functions first, nice-to-haves last
save different versions
know every line of code (LOC or SLOC)
look at all variables
use debug statements and a debugger tool
12

23. “Wiring” programming
overview.
Arduino programs are known as “sketches”
Every program has at least two routines
a. setup( )
b. loop( )
digital and analog input / output
serial communications
13

24. Arduino sketch.
// set pin numbers:
Declare global
const int buttonPin = 2;
const int ledPin = 13;
// the number of the pushbutton pin
// the number of the LED pin
variables and
int buttonState = 0; // variable for reading the pushbutton status
constants
void setup() {
// initialize the LED pin as an output:
pinMode(ledPin, OUTPUT);
// initialize the pushbutton pin as an input:
}
pinMode(buttonPin, INPUT);
Setup pins and
baud rate
void loop(){
// read the state of the pushbutton value:
buttonState = digitalRead(buttonPin);
// check if the pushbutton is pressed.
// if it is, the buttonState is HIGH:
if (buttonState == HIGH) {
// turn LED on:
digitalWrite(ledPin, HIGH);
Loop
}
else {
continuously
// turn LED off:
digitalWrite(ledPin, LOW);
}
}
14

25. Arduino sketch commands
pinMode( )
serial.Begin( )
serial.Read( )
digitalRead( )
digitalWrite( )
analogRead( )
analogWrite( )
delay( )
millis( )
randomSeed( )
random( )
pulseIn( )
ShiftOut( )
15

26. “Processing”
programming language.
Combination of programming language and
development environment that runs on personal
computer (Windows, Linux, or Mac).
Can listen for packets from MCU and process
using the power of the PC.
Can use more powerful software such as Flash,
Visual Basic, C#, Java to manipulate/display/
interact with the data from the MCU.
Export to applets for the Web or desktop app.
16

27. more on “Processing”
Every piece of software written in Processing has:
a. setup( )
b. draw( )
Import libraries
a. import processing.serial.*;
b. Serial myPort;
Draw and Redraw
Easy to interface with graphics, video, sound, mouse,
keyboard, web, text files
17

28. “Processing” sketch.
void setup() {
size(400, 400); Declare
stroke(255); variables and
}
screen
void draw() { characteristics
background(192, 64, 0);
line(150, 25, mouseX, mouseY);
}
draw is the main
loop that runs
continuously
18

29. understanding
data packets.
Create packet of data, based on sensor inputs and
computed values to be transmitted on a repetitive
or as needed basis.
System
Header Sensor1 Sensor2 Status Trailer
(8 bits) (32 bits) (32 bits) Flags (8 bits)
(8 bits)
88 BIT DATA PACKET
19

30. understanding
data packets.
Create packet of data, based on sensor inputs and
computed values to be transmitted on a repetitive
or as needed basis.
System
Header Sensor1 Sensor2 Status Trailer
(8 bits) (32 bits) (32 bits) Flags (8 bits)
(8 bits)
88 BIT DATA PACKET
Alarm Status Operating Mode Comm Mode Failure
(2 bits) (3 bits) (2 bits) (1 bit)
19

31. understanding
data packets.
Bitwise logic operations
Bitmasking
Checksum
Parity Bits
Start Bit / Stop Bit
Binary Coded Decimal (BCD)
ASCII versus Raw Byte (Raw limited 0 -> 255)
Message Handling
a. Punctuation using delimiting character
b. Call and Response (Handshaking)
20

32. other software skills.
Get to know Hypertext Markup Language (HTML),
mySQL (Standard Query Language), and Hypertext
Preprocessor (PHP). Will be useful for writing apps that
interact over the Internet.
Get some web space that supports PHP and mySQL.
Use a good Serial Communication app such as PuTTY.
Also try Gobetwtino (Windows only).
Always check to see if someone has written a library
before writing your own code. No need to reinvent the
wheel. Give credit though!
21

33. A look at the hardware side.
22

34. electrical engineering 101.
Voltage (volts): electrical potential
- 5V = ‘1’, true, on. 0V = ‘0’, false, off (Digital)
Current (amps): rate of electron flow
Resistance (ohms, Ω): opposition of flow of current
Ground: 0V potential, where current wants to flow to
Power (Watt): The rate at which energy is consumed
Capacitance (farads): Ability to store electrical charge.
Digital versus Analog: Discrete versus Continuous
Conventional current flows high potential to low potential. in reality,
electrons are repelled from negative and attracted to the positive.
Components: resistor, capacitor, 555 timer, op-amps, LED,
photocell, thermistor, inductor, diode, transistor, H-bridge, battery,
speaker, transformer, mic, piezo buzzer
23

35. electrical engineering 101.
Voltage (volts): electrical potential
- 5V = ‘1’, true, on. 0V = ‘0’, false, off (Digital) RESISTOR
Current (amps): rate of electron flow
Resistance (ohms, Ω): opposition of flow of current
Ground: 0V potential, where current wants to flow to
Power (Watt): The rate at which energy is consumed
Capacitance (farads): Ability to store electrical charge.
Digital versus Analog: Discrete versus Continuous
Conventional current flows high potential to low potential. in reality,
electrons are repelled from negative and attracted to the positive.
Components: resistor, capacitor, 555 timer, op-amps, LED,
photocell, thermistor, inductor, diode, transistor, H-bridge, battery,
speaker, transformer, mic, piezo buzzer
23

36. electrical engineering 101.
Voltage (volts): electrical potential
- 5V = ‘1’, true, on. 0V = ‘0’, false, off (Digital) CAPACITOR
Current (amps): rate of electron flow
Resistance (ohms, Ω): opposition of flow of current
Ground: 0V potential, where current wants to flow to
Power (Watt): The rate at which energy is consumed
Capacitance (farads): Ability to store electrical charge.
Digital versus Analog: Discrete versus Continuous
Conventional current flows high potential to low potential. in reality,
electrons are repelled from negative and attracted to the positive.
Components: resistor, capacitor, 555 timer, op-amps, LED,
photocell, thermistor, inductor, diode, transistor, H-bridge, battery,
speaker, transformer, mic, piezo buzzer
23

37. electrical engineering 101.
Voltage (volts): electrical potential
- 5V = ‘1’, true, on. 0V = ‘0’, false, off (Digital)LIGHT EMITTING DIODE
Current (amps): rate of electron flow
Resistance (ohms, Ω): opposition of flow of current
Ground: 0V potential, where current wants to flow to
Power (Watt): The rate at which energy is consumed
Capacitance (farads): Ability to store electrical charge.
Digital versus Analog: Discrete versus Continuous
Conventional current flows high potential to low potential. in reality,
electrons are repelled from negative and attracted to the positive.
Components: resistor, capacitor, 555 timer, op-amps, LED,
photocell, thermistor, inductor, diode, transistor, H-bridge, battery,
speaker, transformer, mic, piezo buzzer
23

38. electrical engineering 101.
Voltage (volts): electrical potential
- 5V = ‘1’, true, on. 0V = ‘0’, false, off (Digital) DIODE
Current (amps): rate of electron flow
Resistance (ohms, Ω): opposition of flow of current
Ground: 0V potential, where current wants to flow to
Power (Watt): The rate at which energy is consumed
Capacitance (farads): Ability to store electrical charge.
Digital versus Analog: Discrete versus Continuous
Conventional current flows high potential to low potential. in reality,
electrons are repelled from negative and attracted to the positive.
Components: resistor, capacitor, 555 timer, op-amps, LED,
photocell, thermistor, inductor, diode, transistor, H-bridge, battery,
speaker, transformer, mic, piezo buzzer
23

39. electrical engineering 101.
Voltage (volts): electrical potential
- 5V = ‘1’, true, on. 0V = ‘0’, false, off (Digital) INDUCTOR
Current (amps): rate of electron flow
Resistance (ohms, Ω): opposition of flow of current
Ground: 0V potential, where current wants to flow to
Power (Watt): The rate at which energy is consumed
Capacitance (farads): Ability to store electrical charge.
Digital versus Analog: Discrete versus Continuous
Conventional current flows high potential to low potential. in reality,
electrons are repelled from negative and attracted to the positive.
Components: resistor, capacitor, 555 timer, op-amps, LED,
photocell, thermistor, inductor, diode, transistor, H-bridge, battery,
speaker, transformer, mic, piezo buzzer
23

40. electrical engineering 101.
Voltage (volts): electrical potential
- 5V = ‘1’, true, on. 0V = ‘0’, false, off (Digital) INTEGRATED CIRCUIT
Current (amps): rate of electron flow
Resistance (ohms, Ω): opposition of flow of current
Ground: 0V potential, where current wants to flow to
Power (Watt): The rate at which energy is consumed
Capacitance (farads): Ability to store electrical charge.
Digital versus Analog: Discrete versus Continuous
Conventional current flows high potential to low potential. in reality,
electrons are repelled from negative and attracted to the positive.
Components: resistor, capacitor, 555 timer, op-amps, LED,
photocell, thermistor, inductor, diode, transistor, H-bridge, battery,
speaker, transformer, mic, piezo buzzer
23

41. electrical engineering 101.
Voltage (volts): electrical potential
- 5V = ‘1’, true, on. 0V = ‘0’, false, off (Digital) PHOTOCELL
Current (amps): rate of electron flow
Resistance (ohms, Ω): opposition of flow of current
Ground: 0V potential, where current wants to flow to
Power (Watt): The rate at which energy is consumed
Capacitance (farads): Ability to store electrical charge.
Digital versus Analog: Discrete versus Continuous
Conventional current flows high potential to low potential. in reality,
electrons are repelled from negative and attracted to the positive.
Components: resistor, capacitor, 555 timer, op-amps, LED,
photocell, thermistor, inductor, diode, transistor, H-bridge, battery,
speaker, transformer, mic, piezo buzzer
23

42. electrical engineering 101.
Voltage (volts): electrical potential
- 5V = ‘1’, true, on. 0V = ‘0’, false, off (Digital) TRANSISTOR
Current (amps): rate of electron flow
Resistance (ohms, Ω): opposition of flow of current
Ground: 0V potential, where current wants to flow to
Power (Watt): The rate at which energy is consumed
Capacitance (farads): Ability to store electrical charge.
Digital versus Analog: Discrete versus Continuous
Conventional current flows high potential to low potential. in reality,
electrons are repelled from negative and attracted to the positive.
Components: resistor, capacitor, 555 timer, op-amps, LED,
photocell, thermistor, inductor, diode, transistor, H-bridge, battery,
speaker, transformer, mic, piezo buzzer
23

43. electrical engineering 101.
Voltage (volts): electrical potential
- 5V = ‘1’, true, on. 0V = ‘0’, false, off (Digital)
Current (amps): rate of electron flow
Resistance (ohms, Ω): opposition of flow of current
Ground: 0V potential, where current wants to flow to
Power (Watt): The rate at which energy is consumed
Capacitance (farads): Ability to store electrical charge.
Digital versus Analog: Discrete versus Continuous
Conventional current flows high potential to low potential. in reality,
electrons are repelled from negative and attracted to the positive.
Components: resistor, capacitor, 555 timer, op-amps, LED,
photocell, thermistor, inductor, diode, transistor, H-bridge, battery,
speaker, transformer, mic, piezo buzzer
23

44. nodes and loops.
Circuit must be a
continuous loop.
Sum of all voltage
drops and gains
around a loop is 0V.
Current into a node
equals current out of a
node.
24

45. limiting current.
Ohm’s Law: V=I*R
5V = 3V + (Imax * R)
5V = 3V + 7mA * R
0.007A * R = 2V
Imax 3V
R = 286Ω
5V
P = I2R
P = (.007A)2 * 286Ω
P = 0.014W = 14mW
300Ω, 1/8W resistor will suffice.
To be safe, pick components that
have slightly larger values then
calculated requirements.
25

46. signals theory.
An electrical signal has 3 key
attributes that vary with time:
a. Frequency
b. Amplitude
c. Phase
Communications
Baud rate: bits per second, two
devices must “talk” at same
baud rate
Simplex, Half-Duplex, Full-
Duplex comm channels
Overall comms speed based on
Bandwidth (bits per second) and
Latency (milliseconds)
26

47. digital logic gates.
Floating gate: A digital
device gets confused if it
doesn’t see ground or 5V.
Causes of confusion: RF
noise, static electricity.
Typically a problem with
switches.
Need a pull-up or pull-down
resistor to eliminate high
problems resulting from
floating gates.
Other issue: Switch
bounce. “Debounce” can
be done in hardware or
software
27

48. digital logic gates.
Floating gate: A digital
device gets confused if it
doesn’t see ground or 5V.
Causes of confusion: RF
noise, static electricity.
Typically a problem with
switches.
Need a pull-up or pull-down
resistor to eliminate high
problems resulting from
floating gates.
Other issue: Switch
bounce. “Debounce” can
be done in hardware or
software
27

49. digital logic gates.
Floating gate: A digital
device gets confused if it
doesn’t see ground or 5V.
Causes of confusion: RF
noise, static electricity.
Typically a problem with
switches.
Need a pull-up or pull-down
resistor to eliminate high
problems resulting from
floating gates.
Other issue: Switch
bounce. “Debounce” can
be done in hardware or
software
27

50. digital logic gates.
Floating gate: A digital
device gets confused if it
doesn’t see ground or 5V.
Causes of confusion: RF
noise, static electricity.
Typically a problem with
switches.
Need a pull-up or pull-down
resistor to eliminate high
problems resulting from
floating gates.
Other issue: Switch
bounce. “Debounce” can
be done in hardware or
software
27

51. feedback loops.
The output of the
system is fed back to
the system as an
additional input.
Adds complexity.
Timing becomes
crucial when multiple
objects are linked.
28

52. analog to digital.
MCU can “deal” with analog
only after analog-to-digital
converter (ADC) digitizes or
quantizes the analog signal.
Resolution is based on
number of bits and
sensitivity of ADC.
Example: ADC with 10V
reference voltage and 12-bit
resolution. 2^12 = 4096.
Number of steps:
2#bits - 1
10V/4096 means MCU can
read between at at 2.44 mV Resolution:
resolution. Voltage Range / 2#bits
29

53. voltage dividers.
Voltage Divider
Used to drop voltage to
required level.
Input to microcontroller if you
replace R1 with a sensor that is
based on variable resistance.
Vout = Vin * [R2 / (R1+R2) ]
- R1 -> 0, then Vout = Vin
- R1 -> Infininity, Vout = 0
What happens if variable
resistor is on bottom?
30

54. transistors and gates.
Sourcing versus Sinking
a. Source current to device
b. Sink current from device to ground.
Common Anode / Common Cathode
Gate Fan-In / Fan-Out
Serial versus Parallel
CMOS-TTL interfacing
Bipolar Power Supply
31

55. transistors and gates.
Sourcing versus Sinking
a. Source current to device
b. Sink current from device to ground.
Common Anode / Common Cathode
Gate Fan-In / Fan-Out
Serial versus Parallel
CMOS-TTL interfacing
Bipolar Power Supply
31

56. transistors and gates.
Sourcing versus Sinking
a. Source current to device
b. Sink current from device to ground.
Common Anode / Common Cathode
Gate Fan-In / Fan-Out
Serial versus Parallel
CMOS-TTL interfacing
Bipolar Power Supply
31

57. transistors and gates.
Sourcing versus Sinking
a. Source current to device
b. Sink current from device to ground.
Common Anode / Common Cathode
Gate Fan-In / Fan-Out
Serial versus Parallel
CMOS-TTL interfacing
Bipolar Power Supply
31

58. transistors and gates.
Sourcing versus Sinking
a. Source current to device
b. Sink current from device to ground.
Common Anode / Common Cathode
Gate Fan-In / Fan-Out
Serial versus Parallel
CMOS-TTL interfacing
Bipolar Power Supply
31

59. transistors and gates.
Sourcing versus Sinking
a. Source current to device
b. Sink current from device to ground.
Common Anode / Common Cathode
Gate Fan-In / Fan-Out
Serial versus Parallel
CMOS-TTL interfacing
Bipolar Power Supply
31

60. transistors and gates.
Sourcing versus Sinking
a. Source current to device
b. Sink current from device to ground.
Common Anode / Common Cathode
Gate Fan-In / Fan-Out
Serial versus Parallel
CMOS-TTL interfacing
Bipolar Power Supply
31

61. amplifiers and filters.
Amplifier Circuits built using
Operational Amplifiers (Op-Amps):
a. Inverting (Av = -Rf / Rin)
b. Non-Inverting (Av = 1+Rf/Rin)
c. Differentiating
d. Integrating
e. Summing
f. Subtractor
Filters
a. High-pass
b. Low-pass
c. Bandpass
d. Bandstop (Notch)
32

62. amplifiers and filters.
Amplifier Circuits built using
Operational Amplifiers (Op-Amps):
a. Inverting (Av = -Rf / Rin)
b. Non-Inverting (Av = 1+Rf/Rin)
c. Differentiating
d. Integrating
e. Summing
f. Subtractor
Filters
a. High-pass
b. Low-pass
c. Bandpass
d. Bandstop (Notch)
32

63. amplifiers and filters.
Amplifier Circuits built using
Operational Amplifiers (Op-Amps):
a. Inverting (Av = -Rf / Rin)
b. Non-Inverting (Av = 1+Rf/Rin)
c. Differentiating
d. Integrating
e. Summing
f. Subtractor
Filters
a. High-pass
b. Low-pass
c. Bandpass
d. Bandstop (Notch)
32

64. amplifiers and filters.
Amplifier Circuits built using
Operational Amplifiers (Op-Amps):
a. Inverting (Av = -Rf / Rin)
b. Non-Inverting (Av = 1+Rf/Rin)
c. Differentiating
d. Integrating
e. Summing
f. Subtractor
Filters
a. High-pass
b. Low-pass
c. Bandpass
d. Bandstop (Notch)
32

65. amplifiers and filters.
Amplifier Circuits built using
Operational Amplifiers (Op-Amps):
a. Inverting (Av = -Rf / Rin)
b. Non-Inverting (Av = 1+Rf/Rin)
c. Differentiating
d. Integrating
e. Summing
f. Subtractor
Filters
a. High-pass
b. Low-pass
c. Bandpass
d. Bandstop (Notch)
32

66. amplifiers and filters.
Amplifier Circuits built using
Operational Amplifiers (Op-Amps):
a. Inverting (Av = -Rf / Rin)
b. Non-Inverting (Av = 1+Rf/Rin)
c. Differentiating
d. Integrating
e. Summing
f. Subtractor
Filters
a. High-pass
b. Low-pass
c. Bandpass
d. Bandstop (Notch)
32

67. inductive loads and
decoupling capacitors.
Inductive vs. Resistive Loads
Blowback Voltage
a. When transistor turns off,
motion of magnets in motor
decelerating will induce back
voltage across coils.
b. Flywheel or Snubber diode
allows voltage to dissipate safely.
Always put diode in parallel to
inductive load.
Can also be in parallel to Collector-
Emitter of transistor.
Need decoupling capacitors
across Vdd and GND of all ICs and
Voltage Regulators when you have
inductive loads.
33

68. inductive loads and
decoupling capacitors.
Inductive vs. Resistive Loads
Blowback Voltage
a. When transistor turns off,
motion of magnets in motor
decelerating will induce back
voltage across coils.
b. Flywheel or Snubber diode
allows voltage to dissipate safely.
Always put diode in parallel to
inductive load.
Can also be in parallel to Collector-
Emitter of transistor.
Need decoupling capacitors
across Vdd and GND of all ICs and
Voltage Regulators when you have
inductive loads.
33

69. inductive loads and
decoupling capacitors.
Inductive vs. Resistive Loads
Blowback Voltage
a. When transistor turns off,
motion of magnets in motor
decelerating will induce back
voltage across coils.
b. Flywheel or Snubber diode
allows voltage to dissipate safely.
Always put diode in parallel to
inductive load.
Can also be in parallel to Collector-
Emitter of transistor.
Need decoupling capacitors
across Vdd and GND of all ICs and
Voltage Regulators when you have
inductive loads.
33

70. pulse width modulation.
Pulse Width Modulation,
abbreviated PWM.
“Faking” an analog output
signal by adjusting the
on / off cycle (aka duty
cycle) of a digital signal.
Equivalent power to
20% YIELDS 2.4V
continuous voltage. 50% YIELDS 6V
80% YIELDS 9.6V
Vout = (Ton/Toff) * Vdigital 100% YIELDS 12V (ALWAYS ON)
34

71. hysteresis
Systems where inputs fluctuate rapidly near a
threshold value result in noisy output.
Hysteresis can be used to filter signals so that the
output reacts slowly by taking recent history into
account.
For example, a thermostat controlling a heater may
turn the heater on when the temperature drops
below A degrees, but not turn it off until the
temperature rises above B degrees. This prevents
rapid switching on and off as the temperature drifts
around the set point. Resulting in less voltage
spikes and wear-and-tear on equipment.
A Schmitt trigger is a simple electronic circuit that
also exhibits this property. Often, some amount of
hysteresis is intentionally added to an electronic
circuit (or digital algorithm) to prevent unwanted
rapid switching. This and similar techniques are
used to compensate for contact bounce in
switches, or noise in an electrical signal.
35

72. scaling functions.
Sometimes the range of your inputs doesn’t match
the values of your outputs.
Need a scaling function to adjust for variances in
the two.
OUTPUT DEVICE INPUT SENSOR
2000 500
Output Pulsewidth =
(sensorValue - min. sensorValue) x Output pulseRange
_______________________________________________ + min. Output
Input sensorRange pulseWidth
sensor Value
Pulsewidth
Output Input
Range: Range:
1000 470
1000 30
36

73. other electrical concepts.
Smoothing, Sampling, Averaging
Sometimes noise is added by the environment, sensor imperfections, or supporting
circuit.
Need to reduce that noise for performance.
a. Smoothing: If sensor output, at rests, continuously bounces by 3, then divide
output by 3 before using in computations. Cost of smoothed sensor reading is
loss of resolution. Useful if output has small, finite states.
b. Averaging: Take mean of last X sensor readings. Or keep array and sort each
new reading, then take median.
c. Sampling: Read sensors at twice the highest frequency component of observed
phenomenon to reduce ambiguity. See Nyquist Criterion.
Threshold, Edge, Peak
a. Threshold: Detect is signal goes above/drops below certain value. May need to build in
hysteresis for signals the hover around the threshold to eliminate constant fluctuations.
b. Edge Detection: Detect a rising or falling edge of a signal. Use hysteresis to detect when
signal hits the 10% and 90% mark of the final value.
c. Peak detection: Ensure signal is above/below threshold value. Constantly measure
signal input and compare to previous value. When new reading is less than previous
reading, then peak has been reached.
d. Signal Skew: Output signal slow to respond to change in input signal. Measure at 50%.
e. Signal Slew: Slow rise or fall time of signal. Measure between 10% and 90%.
37

74. more about electronics.
Tools you will need:
a. Variable temperature soldering iron, solder (60/40 .32”), flux,
solder braid, solder sucker
b. Digital multimeter
c. USB oscilloscope
d. Wire strippers, needle nose pliers
e. Magnifying class
f. Anti-static pad and wrist strap
g. Alligator clips
h. Breadboards (various sizes)
i. Long reach tweezers
j. Precision screwdriver set
k. IC chip extractor / inserter
l. “Third hand” tool
m.Calipers
38

75. types of sensors and actuators.
Sensors (input transducers, from the real-world to the computer)
Beware of sensor drift, use redundant and independent sensors.
a. infrared
b. pressure
c. temperature
d. magnetic
e. microphone
f. RFID reader
g. photodiode
h. strain gauge
i. accelerometers
Output transducers or indicators (from the computer to real-world)
a. radios / antenna
b. light bulb / LED
c. speaker / buzzer
d. screens / monitors
Actuators (creating motion)
a. dc motor
b. servo
c. piezoelectric motor
39

76. using a multimeter.
Analog versus digital
Auto-ranging
Polarity check
Continuity check
Measure current, voltage, resistance, capacitance
Diode and transistor check
40

77. using an oscilloscope.
Measure voltage over time.
Watch electrical signal over time
as waveform.
Can be digital, analog, or PC-
based (USB).
Measure in both time and
frequency domains (via a Fast
Fourier Transform or FFT)
Other useful equipment:
Function generator
DC power supply
Logic analyzer
41

78. soldering techniques.
Use soldering iron with adjustable temperature, let soldering iron get hot.
Heat the joint, not the solder.
Clean component leads and PCB before.
Usually used .32” 60/40 solder.
Smaller joints are better joints.
Keep tip clean, tin your tip smoothly.
Side of tip gets hotter than the very tip of the soldering iron (larger surface area).
Keep moist sponge.
Use flux, desoldering vacuum, solder wick, helping hands tool, tweezers, heat
sinks.
Ensure room is well ventilated as solder contains lead.
Turn soldering iron off when done.
42

79. other hardware skills.
RF and IR wireless links.
Want to do home automation? Try X10 hardware.
There is an Wiring library to interface with X10.
XBee radios do the “dirty” work of controlling RF
communications between microcontrollers.
43

80. thermal management with heat sinks
High current and high frequency devices can generate a lot of
heat which can damage components, especially ICs.
Dissipate heat through the device (radiation), heat sinks
(conduction), and fans (convection).
Thermal Resistance (θja) is the measure of how efficiently heat
is transferred across the boundary between two different
mediums. Measured in °C/W
θja: Overall thermal resistance
θcs: Thermal resistance of thermal paste
θjc: Thermal resistance of the package
θsa: Thermal resistance of heat sink
TJ: Temperature of device/package junction
TA: Temperature of ambient air
TS: Temperature of heat sink
TC: Temperature of device case
P: Power (Watts, P = IV)
θja (with heat sink) = θcs + θjc + θsa = (TJ - TA) / P
θja (without heat sink) = θjc + θca = (TJ - TA) / P
Lower thermal resistance means better heat sink. Heat sinks
with large surface area and good air circulation gives best heat
dissipation. Don’t forget the thermal paste!
44

81. sizing the heat sink
Given: Find heatsink with θsa <= 6.8°C/W
θja = 8°C/W θjc = 0.2°C/W
θcs = 0.5°C/W TJmax = 85°C Ex. Part# 240-12.7B has θsa = 6°C/W and
TAmax = 70°C Vmax = 3.3V Imax = .6A meets dimensional requirements.
P = IV = .6A x 3.3V = 1.98W to dissipate Verify it will work.
P <= (TJ - TA) / θja = (85°C - 70°C) / 8°C/W TJ = [ (θcs + θjc + θsa) x P ] + TA
TJ = 78.7°C
P <= 1.85W
TJmax = 85°C
1.98W is NOT less than 1.85W, therefore
78.7°C < 85°C, therefore good to use.
heat sink is required. Use 10%-15%
safety factor in actual application.
NOTE: If 15% safety margin was used...
θja = (TJ - TA) / P = (85°C - 70°C) / 1.98W
78.7°C x 1.15 = 90.5°C
θja = 7.5°C/W 90.5°C is NOT less than 85°C, therefore
heat sink 240-12.7B is not a good choice.
θja = θcs + θjc + θsa
7.5°C/W = 0.2°C/W + θsa + 0.5°C/W
θsa <= 6.8°C/W
45

82. Putting hardware and
software together.
It is an irrelevant argument as to whether software or
hardware is “better”. Both are necessary, and you will be
the master when you know when to use each.
46

83. a complete design from
concept to product.
Concept: A system that reads an RFID tag,
validates identity, and adjust lights to user’s
preferences.
First outline and diagram what needs to be
designed.
Simulate hardware design.
Write code, stub in hardware interaction
Validate user
Read RFID tag Control lights
Recall preferences
47

84. a complete design from
concept to product.
Determine what components are required.
a. Which microcontroller, sensor, actuator, etc?
b.What will be done in hardware and what will be
done in software?
Validate user
Read RFID tag Control lights
Recall preferences
RFID MICROCONTROLLER X10
TAG 48 CONTROL
READER UNIT

85. a complete design from
concept to product.
Determine what components are required.
a. Which microcontroller, sensor, actuator, etc?
b.What will be done in hardware and what will be
done in software? FUNCTIONAL
Validate user
Read RFID tag Control lights
Recall preferences
RFID MICROCONTROLLER X10
TAG 48 CONTROL
READER UNIT

86. a complete design from
concept to product.
Determine what components are required.
a. Which microcontroller, sensor, actuator, etc?
b.What will be done in hardware and what will be
done in software? PHYSICAL
Validate user
Read RFID tag Control lights
Recall preferences
RFID MICROCONTROLLER X10
TAG 48 CONTROL
READER UNIT

87. when to use hardware
versus software.
When to “do it” in hardware
a. Speed is a concern.
b. PCB real estate is not a concern.
c. Recurring per unit costs.
d. If it is easier to do in hardware than
software, such as CRC circuit.
When to “do it” in software
a. Adaptable, quick/easy changes.
b. Data that varies from user to user.
c. Once implemented/tested, no more per
unit costs.
d. If there are fast, simple, powerful libraries
available to perform certain functions.
Both have advantages/disadvantages!
49

88. when to use hardware
versus software. ICs
IR LED
When to “do it” in hardware Transistor
a. Speed is a concern. Capacitor
b. PCB real estate is not a concern.
c. Recurring per unit costs.
d. If it is easier to do in hardware than
software, such as CRC circuit.
When to “do it” in software
a. Adaptable, quick/easy changes.
b. Data that varies from user to user.
c. Once implemented/tested, no more per
unit costs.
d. If there are fast, simple, powerful libraries
available to perform certain functions.
Both have advantages/disadvantages!
49

89. when to use hardware
versus software. ICs
IR LED
When to “do it” in hardware Transistor
a. Speed is a concern. Capacitor
b. PCB real estate is not a concern.
c. Recurring per unit costs.
d. If it is easier to do in hardware than
software, such as CRC circuit.
When to “do it” in software
a. Adaptable, quick/easy changes.
main( )
b. Data that varies from user to user.
function1( )
c. Once implemented/tested, no more per
int x
unit costs.
float y
d. If there are fast, simple, powerful libraries
available to perform certain functions.
Both have advantages/disadvantages!
49

90. a complete design from
concept to product.
Design architecture
Identify what to do in HW and SW, define
interfaces.
Design and build HW and SW components, test
and debug separately.
Integrate hardware and software.
Test, debug, test, debug, ...
Document, document, document THROUGHOUT.
50

91. common mistakes.
Remember Occam’s Razor and be methodical in troubleshooting the following:
a. Not hooking up ground or power.
b. Reversing ground and power.
c. Connecting power/ground to wrong IC pin.
d. Connecting to different pin then what is written in the software.
e. Not supplying sufficient power.
f. No pull-up/pull down resistor on I/O pin.
g. “Dirty” power supply.
h. Switch bounce.
i. Wrong resolution.
j. Mixing up the TX and RX pins.
k. Wrong serial port.
l. Another application is controlling the serial port.
m. Incompatible baud rates.
n. Bad components (not the microcontroller or software’s fault)
o. Bent IC pin or chip in backwards.
p. ASCII versus raw byte.
q. Poor soldering job, shorted traces or pins.
r. Something was miscoded in software -- remember code, debug, code, ...
51

92. hardware you’ll come to know.
Switches Battery (Cells) Antenna
Normally Open vs. Normally Closed
Momentary vs. Toggle Motors
Make-then-break, Break-then-make DC Analog-to-Digital Converter
Poles and Throws (SPST, SPDT) Stepper RC Network and RCTime Function
Foot RC Servo if ADC unavailable on uC
Tape Silicon Controlled Rectifier (SCR) Digital-to-Analog Converter
Roller DIAC / TRIAC Operational Amplifier
Whisker Transistors Audio Amplifier
Micro BJT (Higher current capability) Schmitt Trigger (Hysteresis)
Tilt NPN (N.O.) Liquid Crystal Display (LCD)
Reed (magnetic) PNP (N.C.) Piezoelectric Devices
Wire (AWG number) Darlington Pair H-Bridge
Solid FET (Faster, low power) Bridge Rectifier
Braided JFET Power Inverter
Coaxial MOSFET Opto-Isolator
Twister Pair Enhancement Ground / Earth / Chassis
Resistors Depletion Digital and Analog (Linear) Integrated
Circuits (ICs
Fixed vs. Variables Incandescent Bulbs 555 timer
Potentiometer (pot) Oscillator F/V and V/F converter
Rheostat Microphone Vibrating motor
Thermistor Speaker PTC fuse
Photoresistor Voltage Regulator RFID reader
Flex Digital Logic Gates Rectifier
Force Sensitive AND Header, socket, jacks
Capacitors OR IR transmitter / receiver
varactor NAND Vibratab
polarized NOR PIR sensor
non-polarized XOR Ultrasonic ranging sensor
Inductors XNOR Line sensor
chokes NOT (Inverter) Hall sensor
transformers Buffer (Tri-State Buffer) RF transmitter/receiver pair
solenoids (linear motion) Flip-Flop Accelerometer
Mechanical relays Latch Pressure sensor
Solid State Relays Shift Register Temperature sensor
Ferrite beads Encoder / Decoder GPS
Boards Multiplexer / Demultiplexer Bluetooth / WiFi / Ethernet module
Breadboard Transmission gate Wheatstone bridge
Perforated Board Diodes (anode + / cathode -) Heat sinks
Copper Etch Zener
Printed Circuit Board (PCB) Light-Emitting (LED)
Varistors 7-Segment Display
Varactor Schottky
Sidactor Tunnel
Fuses Photodiode
52

93. staying focused.
you can do it!
Keep an engineering journal and track every idea.
Stay high level.
Don’t over plan, experiment a lot.
a. However, don’t just start coding or hooking up
components. Spend the time doing paper design,
flowcharts, and prototype individual subsystems.
b. Try some circuit simulators such as TINA and EDISON.
Collaborate with others.
Spend time learning mechanical motions and materials too.
a. Levers, Gears, Pulleys, Ratchets, Cam, Joint, Pistons,
Linkages. (Keep your LEGOs!)
b. Metals, Plastics, Adhesives, Conductive cloth and
thread. Conductor versus Insulators.
53

94. where to shop.
www.adafruit.com
www.sparkfun.com
www.parallax.xom
www.goldmine-elec.com
www.digikey.com
www.jameco.com
www.makershed.com
Also, many vendor will offer free samples. Fairchild, National
Semiconductor, and Microchip for example. Check out www.ladyada.net
Spec Sheets
Important to learn how to read schematics and understand circuit
symbols.
www.symbols.net/electrical
www.octopart.com
54

95. where to find out more.
www.michaelbparks.com
blog: Geek Cowboy (blog.geekcowboy.net)
email: mike@michaelbparks.com
www.arduino.cc
www.processing.org
www.makezine.com
www.ladyada.net
Guide to Programmable Logic Controllers
PC / Arduino Proxy Interface
Igoe, Tom. Making Things Talk and Physical Computing
Platt, Charles. Make: Electronics
Banzi, Massimo. Getting Started with Arduino
Mims, Forrest. Engineering Notebooks.
55

96. Questions?

97. Backup Slides
57

98. typical problems and
solutions.
Problems
a. Ground loops
b. Cross talk
c. Noise
d. Jitter
e. Skew
f. EMI
g. Ringing
h. Spikes / Droop
Solutions
a. Bypass
b. Decouple
c. Shielding
d. Layout
e. Ground plane
f. Hierarchy / abstraction in design
g. Regularity
h. Modularity
i. Locality
58

99. power.
Real Power: Watts. P = V*I*cos(phase angle)
- DC power, phase angle = 0, cos(0) = 1, therefore P=VI
Reactive Power: VARs. Q = V*I*sin(phase angle)
Complex or Apparent Power: Volt-Ampere, VAs. S = V*I
S = P + jQ, S2 = P2 + Q2
Power Factor = Real Power / Apparent Power.
- Ideal PF is 1.
Power is the rate at which energy is consumed,
measured in joules per second.
Energy is measured in joules or more common;y
Kilowatt-Hour (kWHr)
59

100. more power.
Batteries: Rated in mA-Hr.
A 1000 mA-Hr batter can source 1000 mA for 1 hour.
Supply correct voltage, but can over supply current.
A 12V, 3A source can power 3 12V, 1A devices.
Increase voltage, can spin a wheel faster. Increase current, can spin a larger
wheel.
Power DC jacks.
DC power jack: power center, ground shield or vice-versa.
Audio Impedance Matching: Source resistance, Speaker resistance.
Square root of source resistance over speaker resistance.
Noise margins
Transformer relations: Np/Ns = Vp/Vs = Is/Ip
Root-Mean-Square (RMS) Voltage: DC equivalent of an AC voltage.
High Impedance (Z)
CIVIL, ELI the ICE man.
60

101. decibels.
Ap (ratio) = Pout / Pin
Ap (bel) = log(Pout/Pin)
Ap (dB) = 10 log10(Pout/Pin)
Vp (dB) = 20 log10(Vout/Vin)
Unity Gain = 0 dB
Multiply ratios, Sum bels.
Gain is to increase, attenuate is to drop
1 bel = 50%
RF (dBm).
1 mW of power transmitted.
dBm = 10 log10 (power received)
- 1mW received: 10 log10 (1 mW) = 0 dBm (ideal)
- .5mW received: 10 log10 (.5 mW) = -3.01 dBm
Bode plot (phase margin)
61

102. flags.
Carry
Zero
Sign
Parity
Overflow
62

103. other topics.
Karnauph Maps
Sequential versus Combinational logic.
Mealy versus Moore machines.
Direct versus Capacitive Coupling
a. Direct: No frequency dependance, attenuates
signal, high input impedance possible
b. Capacitive: Less gain at low freq, less
impedance at high freq, no attenuation, block
unwanted DC components.
Design Abstraction: Behavioral (RTL, VHDL);
Structural (circuit, logic gate, ERC); Physical
(layout, DRC)
63

104. IC package types.
Dual Inline Pins (DIP), socket mount
Small Outline IC (SOIC), surface mount
Plastic Lead Chip Carrier (PLCC)
64

105. constraints.
Design always a competition between:
a. Size
b. Power
c. Speed
d. Cost
65

106. calibration graphs.
Components of the same type will have a wide range of outputs
given the exact same input.
This is why spec sheets tend to give ranges of values.
Seen in such components as ultrasonic range finders or
thermistors.
Need to put completed circuit through set of tests of varying
inputs and measure the outputs, then graph the results. Will help
later in reading sensor results and interpreting their meaning and/
or troubleshooting.
5
Output Voltage
5
3.75 4.25
2.5 3
1.25
1
0
1m 2m 3m 4m
Distance (meters)
66