1. Electronics Fabrication and Assembly Workshop
School of Mechanical Engineering
Electronics Fabrication and Assembly Workshop

2. Objectives Objectives: Transmitting Information
Understanding of Signals and Signal types
Noise and Signal to Noise Ratios
Understanding Electronics Hardware
Review of Basic Components
Understanding Transistors – Bipolar and MOSFET
Understanding of modules and modular design
Basics of Microcontrollers
Arduino + Compact Rio
Understanding of Electronics Sensors
Understanding of Motor types and Motor Controllers
Understanding of types of wire and wire routing
Understanding Fuses and Emergency Stops

3. Objectives continued More Objectives: Schematics and Wiring Diagrams
Instrumentations, Assembly and Troubleshooting
Basics of troubleshooting
Type of Instrumentation
DMM
Oscilloscope
Types of Circuit Boards
Type of Component packages
Basics of Soldering
Cold Solder Joints
Build and test a circuit (project)
To Have Fun!

4. Transmitting Information
Signal types and Noise

5. Types of Signals Types of Signals: Analog Voltage (0-10V)
Sine Wave
Digital (I/O, TTL)
Binary – either ‘ON’ or ‘OFF’
TTL – Transistor to Transistor logic – 5V HI, 0V LOW
Analog Current (4-20mA)
Analog – think of Voltage across a resistor via Ohms law: V=I*R
Commonly used in Industrial Controls
PWM (Pulse Width Modulated) signal
Square wave, variable duty cycle
Serial, Ethernet, GPIB, CAN
Negotiated Protocols for sending data

6. Analog Signal – 0-10V

7. Digital Signal - TTL

8. Current Signal – 4mA – 20mA

9. PWM Signal

10. Noise and Signal to Noise Ratio
Noise is electrical potential energy that is injected into wires in your circuits.
Noise can be generated by numerous sources, some internal to your project and some external
Motors and/or motor drives
Poor wiring practice (crosstalk)
Fluorescent lighting
Ripple from the incomplete conversion of AC power to DC power in power supplies
Electrochemical reactions (in batteries)
Ground loops due to ‘floating’ or high resistance ground connections
The Signal to Noise Ratio is simply the magnitude of your desired signal in relation to the magnitude of the ambient noise. The higher the SNR ratio, the better the noise rejection and purer the desired signal will be.

11. Noise and Signal to Noise Ratio
Noise is something you should consider and account for in your electrical projects. You can reduce noise by several means including:
Good wiring techniques and wire routing
Using ‘bypass’ capacitors on DC power supplies
Using metal shields and shielded wire
Using wire such as twisted pair and/or Coaxial cable
Using good grounding techniques
Use amplifiers to increase the magnitude of signals
Not all noise is important. Understand your signals and what they mean for your project to determine whether ambient noise is something you need to work with.

12. Noise and Signal to Noise Ratio Signal and Noise with similar Vpp and average DC level

13. Noise and Signal to Noise Ratio Signal and Noise with similar Vpp and average DC level
Notice how when the desired signal’s magnitude is very similar to the magnitude of the
ambient noise, the resultant signal is very different than that of the desired signal.

14. Noise and Signal to Noise Ratio Signal and Noise with similar Vpp but different average DC level

15. Noise and Signal to Noise Ratio Signal and Noise with similar Vpp but different average DC level
Notice that even if we shift the desired signal up in voltage, if the magnitude of the signal
remains similar to the magnitude of the ambient noise, our total signal is not
representative of the desired signal

16. Noise and Signal to Noise Ratio Signal and Noise with different Vpp and different average DC level

17. Noise and Signal to Noise Ratio Signal and Noise with different Vpp and different average DC level
Notice how the resultant signal with noise is not significantly different than the original ‘clean’ signal

18. Demo – Crosstalk and Noise
Noise injected from a single wire to parallel wires of different types over a length of 6 feet.

19. Type of Hardware
Electronics Components and Modules

20. Basic Electronic Components
Resistors, capacitors, inductors
used to control current, change frequencies, build passive filters etc
Integrated circuit chips (IC’s)
Can be analog or digital in nature and allow you to complete advanced tasks in a singular package
Op-Amps
Timer
Microcontrollers
Diodes
Used to control direction of current flow. Can be used to convert AC into DC. Also used in protection circuits for motors and power supplies
Transistors
Building blocks for most integrated circuits and microcontrollers
Can be a Bipolar or a MOSFET type
Used in current amplifiers or electronic switches

21. Transistors, bipolar
Known as NPN or PNP based on materials used in construction. Also called small signal transistors.
Three terminals, Base, Collector and Emitter
Fundamentally bipolar transistors are a current amplifier and each has a gain known as hfe.. This is a ratio of current supplied to the Base terminal and the current available at the Emitter terminal. Gains of are common.
Although these are current amplifiers, they can be used as electronic switches
Can be used to interface a microcontroller output to control a 12 volt relay. (image)
Emitter
Input
Collector
Base
Transistor driver for a
12 volt relay coil

22. Transistors, MOSFET
MOSFET may also be called power transistors due to the capability to handle large currents.
MOSFET is Metal Oxide Semiconductor, Field Effect Transistor
Three terminals, Gate, Drain and Source
Fundamentally, MOSFET’s are a switch. When the proper charge is applied to the Gate, current can flow from the drain to the source. In practical terms, zero current is required at the Gate to operate the transistor.
Commonly found in ‘H bridge’ motor drives and other high power amplifiers.
Can be used to interface a small switch to turn on or off a larger motor. (image)
Transistor switch to turn
on/off a motor

23. Basics of Electronic ‘Modules’
A module is a collection of discrete electronic components assembled in a way to serve a specific function. These offer pre-engineered solutions for specific common applications and have well defined input signals and output signals.
Modules come in numerous shapes/size and functions.
Motor drive
Digital Compass
Ultrasonic Range Finder
Microcontroller kit (Arduino)
Some Key Aspects:
Supply Voltage Required
Supply Current Required
Output Drive Capacity (current drive)
Output Signal type
Input Signal type
Input current required
Connectors used

24. Microcontrollers - Software
A microcontroller is a great option to use for complicated functionality. Microcontrollers can have many means of communications, several inputs and outputs of different types and a high level language to configure the device.
A key consideration for your design and software is understanding the states of the outputs for your microcontroller and the results with your machine
Power up – what state are outputs in? Is that condition defined?
Software crash – what happens to your outputs?
Race condition/hung software – what happens?
Timing – how long for input/output to stabilize to be valid?

25. Microcontrollers - Arduino
The Arduino microcontroller is a low cost, versatile option for many senior design projects
There are numerous models ranging from the Arduino Micro to the Mega.
Different models will have differing numbers of Inputs/Outputs (PWM), clock speed, RAM etc
Arduinos use a C syntax codebase with an open source Integrated development environment
Numerous add-ons in a ‘shield’ format to plug directory into the development board.
We have some Arduinos and Intel Galileos available in ME 2042.

26. Microcontrollers – Compact Rio
The Compact Rio (and MyRIO) microcontroller is a moderate cost microcontroller from National Instruments and uses the LabVIEW programming Environment.
There are numerous models ranging 8 slot cDAQ chassis to the single board RIO or MyRIO.
Different models will have differing numbers of Inputs/Outputs (PWM), clock speed, expansion capability
The Compact RIO cDAQ platform takes modules that allow a mix and match set of capabilities. Modules include AI, AO, DIO, Thermocouple, Bridge amplifiers, Motor Drives etc
We have four Compact Rio Chassis available in ME 2042.

27. Sensors Example Types: Key Aspects: Light
Proportional position (IR, ultrasonic, laser)
Digital position (IR, ultrasonic, Laser)
Flex
Accelerometers
Magnetic (reed switch, hall effect)
Acoustic (microphone, piezo)
Linear position (linear potentiometer, LVDT)
Switch (digital on/off)
Strain Gauges
Rotary position (encoders, potentiometers)
Key Aspects:
What is voltage and current required to operate sensor
What is the signal type of its output
Is there a signal conditioner/amplifier required

28. Motors and Motor Drives
Types:
Stepper
Induction
Servo
Solenoid
Brushed/Brushless
Linear
Controllers:
Stepper Drive (1/2 step, full step)
H Bridge
Frequency Drive
PWM speed control
Microcontrollers CANNOT directly power motors – a Motor Drive is required!

29. Stepper Motors
The stepper motor ‘steps’ from angle to angle when asked
Requires a stepper motor drive
Usually requires 3 DIO controls, Enable, Step and Direction.
Motors come in bipolar or 3 phase configurations
Motor is rated in steps per revolution. Using ‘half step’ mode can double resolution.

30. AC Motors – Servo Motor
The AC motor is a simple motor that will rotate when powered. Adding feedback causes it to become a servo motor.
AC Motors come in single phase and 3 phase variants. In general, you cannot do speed control on a single phase motor.
AC three phase motors can use a Frequency Drive to control speed.
External controller coupled to a feedback mechanism can give exact position control

31. DC Motors – Servo Motors
The DC motor is a simple motor that will rotate when powered. Changing the polarity of the power cables will allow you to reverse direction.
Adding feedback causes it to become a servo motor.
Requires a motor drive for speed control
DC Motors use PWM drives
External controller and some type of positional feedback can allow for position control
Brushed DC Motor

32. RC Servo Motor
The RC Servo is an assembly of a motor, potentiometer, gearbox and PCB controller to translate a PWM signal into a position.
These require power and RC PWM signal to operate.
The PWM signal has a period of 20ms. The pulse width will determines position
0.5ms pulse width is minimum, 1.5ms pulse width is neutral and 2.5ms is maximum.
Above translates to full left, middle and full right for RC servo shown
The RC servo is nothing more than a DC motor with feedback controls integrated into the device

33. Common Interface Devices/Modules
Transistor Current Amplifier Module
Used to take a low current drive output from Microcontroller and turn on a solenoid or relay coil
Relay/Solid State Relay
Electrically controlled switch. Relays are mechanical, Solid State Relays are all electronic components
Transistor Switch
Solid State implementation of a relay
Mechanical Switch – for microcontroller input
Method for a microcontroller to understand the state of a mechanical switch (image)
Circuit to interface
switch to
microcontroller

34. Debouncing Mechanical Switches
A mechanical switch used as an input is not a true impulse function. It will oscillate from high to low before stabilizing
Use a switch debouncer to correct this issue

35. Demo – Switch Debouncing
Demo – Impulse Count for a single closure of a mechanical switch

36. Wire and Wire Types Sized by gauge - AWG Solid/Stranded/Coaxial
Smaller gauge number = bigger wire
Current capacity determined by gauge of wire and temperature rise of wire. In general, thicker wire will be smaller gauge number and can carry more current.
Solid/Stranded/Coaxial
Insulation Rating
12V, 300V, 600V Voltage Ratings
Gas + Oil Resistant
High Temperature

37. Sizing Wire Choosing wire size:
Signal wires carry little to no current and can be of a small size. 22 Gauge is a common choice.
Power wires that carry current should be sized based on the maximum temperature rise you wish to have.
We have included in the hands-on packet a wire sizing guide based on a specific portion of the National Electric Code. This is a very conservative table designed for residential wiring but is very commonly used. There are other tables available for specific applications.
Wires get temperature rise from two sources
Direct current in the wire (resistive heating)
Induced current from other wires in the same raceway
They will also get heat through heat transfer of other wires generating heat. (oven effect)
Duty cycle also factors into the required wire size. A low duty cycle load can use a smaller gauge wire than a high duty cycle load.

38. Using Wire and Raceways
Noise
Signal to noise ratio + signal amplifiers
Wires as antenna
Signal Wire
Twisted Pair vs Non Twisted Pair
Coax
Crosstalk
Shielding
Power Wire
Route to avoid signals and interference
Terminal blocks
Raceways + protection
Conduit – rigid and flexible, plastic and metal
Panduit and Wiremold
Plastic/fiberglass loom
Strain Reliefs
Bending Radius

39. Connectors and Modular Design
Connectors are a vital component of modular design.
They allow you to quickly and safely remove and replace components or modules from your machine
They allow for you to ensure proper polarity of your device
Connectors come in many shapes, sizes and ratings. These can be as simple as ring terminals on a barrier strip to more elaborate polarized locking connectors.
Common connectors seen in ME 463
Berg Pins/Header Pins (used on sensors, Arduino boards)
Deans Connectors (batteries)
Tamiya connectors (batteries)
Ring Terminals/Spade Lugs
Screw Terminals
Make sure you have both sides to a connector!!!!!
Make sure if you order a device, you order its connector as well!!!!

40. Mounting Circuit Boards
Most electronic modules will be build on a Printed Circuit board that includes mounting holes. It is essential that the board/device be mounted securely.
Standoffs are plastic/metal fasteners specifically designed to mount circuit boards above a chassis component.
Plastic 4-40 thread stand offs are available for ME 463 from the E-shop
The back of most PCB are conductive and if shorted to the chassis or a moving part will cause electrical issues and damage. Take care to ensure the PCB is insulated and not in contact with your chassis
Additional though should be made with respect to connecting wiring to your devices when laying out your project.
Allow adequate space for wires to route (bend Radius)
Have proper connectors for wires
Use tie straps to secure wiring into a harness and into your project

41. Batteries, Fuses and Master Disconnects
Batteries come in various types – Alkaline, Lithium Ion, NiCD, NiMh, Lead Acid
Capacity is rated in Amp-Hours. Capacity also include max current draw
Batteries should be sized based on run time needs as well as the maximum current draw required. Different battery types will have different max draws based on capacity.
Each type of battery requires a specific type of battery charger. Lithium batteries require a balancing charger and can/will explode if not charged/discharged correctly.
Fuses
Protect batteries against short circuit or over current situations.
Should be placed as close to the battery or power input as feasible in your design.
Come in ‘Fast blow’ and ‘slo-blow’ designs. Sized based on designed power draw of your device
Master Disconnects (Emergency Stops)
You should incorporate some type of disconnect for electrical power to your device
May be incorporated as part of a larger Emergency Stop system

42. Emergency Stop Systems
Any project with a significant hazard should implement an emergency stop system to render the machine ‘safe’
E-stop systems should
De-energize any hazardous voltages or electrical equipment that can cause motion.
De-energize or disconnect any stored energy sources such as pneumatic or hydraulic systems
Render safe any mechanical systems with stored energy (springs, suspended weights)

43. Emergency Stop Systems cont.
Emergency stop systems can be a simple switch or can be more elaborate systems with multiple switches and/or interlocks
As machines get more complicated, interlocks and emergency stops get more complicated.
Include some type of diagnostics for where a fault occurs
Consider what may be faults and what may be warnings
Be sure to understand the sequence of operation for you machine and work to understand and address all failure modes of your machine.

44. Designing and Documenting Circuits

45. Schematics and Wiring Diagrams
Schematics and Wiring diagrams are very similar in nature but not interchangeable.
A schematic is a pictorial representation of your circuit using standard symbols for components.
Schematic’s can be used to create printed circuit boards
Symbols can be either US or International
Example – resistor is either a squiggly line or box
A Wiring Diagram or Wiring Layout is a picture of the connections you will make to the various modules and components in your device.
A Wiring Diagram can be used to create wire harnesses and to troubleshoot integration issues

46. Example Schematic - Inverter
This is a simple 12V DC to 120V AC inverter circuit schematic.
This uses the ‘US’ style of symbols
KiCAD is free software and good choice for creating schematics

47. Example Wiring Diagram - Arduino
Fritzing is a free and popular software package for making wiring diagrams.

48. Example Schematic- Arduino
This is the schematic of the Arduino Wiring Diagram.

49. Instrumentation, Assembly and Troubleshooting

50. Troubleshooting TEST AS YOU GO!!!!!!!
When things fail, test independent components/modules
Be Careful where you test – circuit boards will short if placed on metal chassis!!!
Tools
Digital Multimeter (DMM)
Good for static voltage measurements
Ammeter
Measures current
Oscilloscope
Displays analog waveforms – good for seeing transient behavior
Counter
Counts pulses, displays frequency, duty cycle and other waveform attributes.
Logic Analyzer
Allows for seeing/decoding logic signals and protocol based signals. Useful for identifying timing issues
Common Pitfalls
Lack of a common Ground
Exceeding rated output of devices (current drive capacity)
Shorts/poor wiring technique during assembly
Interference/crosstalk due to improper wire/shielding
Improper mounting of components causing shorts

51. Digital MultiMeters (DMM)
2 Wire Measurements
This is the common method most people are familiar with to measure Voltage/Resistance
4 Wire Measurements
4 wire Measurements are used when the resistance of your device is so low that the resistance of the probe leads will cause error.
Sampling Error on AC signals – DMMs typically expect sinusoidal AC signals when in AC mode. They also use averaging or RMS methods for displaying the voltage it reads at any given time. Low frequency and high frequency AC signals may not read correctly. Use an Oscilloscope to view any time varying signals to ensure you get what you expect.
If making Current measurements, be sure to have a rough estimate of the current you will be measuring and ensure the DMM can handle that current. Blown fuses are common as well. If it exceeds the capacity – use a current shunt.

52. Oscilloscopes
Initial Settings, Timebase (Horizontal) should be set to around 1/frequency of your signal. Volts/Div (Vertical) should be about a quarter of your expected Vpp of your signal. You can then adjust the position dials to center your signal. Once you have found your signal, adjust timebase and V/div as needed.
Be cautious using ‘autoscale’ buttons. These may or may not show you your signal. If there is a connection problem with your signal, you will see noise
Triggering can be used to ‘stop’ the waveform of your signal. Triggering can be internal (rising edge/falling edge) of your signal or external and typically has a level adjustment.
You should use properly matched scope probes to measure small signals. Coaxial cables may load your signal and display distorted signals.
The Ground of the Scope probe is connected to GROUND. If this is connected to a terminal other than ground of a power supply or output, it will short that connection to ground which likely will result in damage to the probe and/or your device.

53. Prototyping Boards Breadboards Perfboard Solderboards
Breadboards are for testing simple circuits on the bench. Breadboards have no place in the actual prototype itself.
Perfboard
Perfboard is the cheapest and most flexible. This is also the most difficult type of board to assemble a circuit cleanly.
Solderboards
Solderboards are perfboards that have plating on one side bridging holes. This plating also makes it possible to solder components to the board.
Printed Circuit Boards (PCB)
These are boards that are custom made with your circuit traces embedded in the copper. This is the type of board you will be assembling in the hands on session.
PCB boards can use surface mount components and be made to odd sizes.
We have a LPKF Circuit Board Fabrication center that will allow you, as an ME student, to create your own custom PCB. See the E-shop for access and details.

54. Basics of Soldering - Components
Through Hole Components
Typical components found in the EE201 kits
Easiest of the components to solder
Surface Mount Components
Think of an computer board/arduino
Much more difficult to assemble, usually requires a printed circuit board
May require special techniques and equipment
Reflow soldering
Hot air soldering

55. Basics of Soldering Required Equipment Basic Technique
Soldering iron, ideally adjustable
Solder, rosin core 60/40 mix. NOT ACID CORE
Sponge, moist – to clean tip of iron
Wire Cutters/Diagonal Cutters
Basic Technique
Heat the joint, not the solder
Think about assembly order before you start.
Use jigs/vises/holders whenever needed
Think about amount of heat applied. Ensure you manage this to avoid damaging sensitive components
Cold Solder Joints
Connection that is soldered but does not fully bond the two components physically and electrically. Generally causes device not to work.

56. Cold Solder Joints

57. Next Step – We build a circuit!
Be sure to come to your hands-on session!