Mechatronics Quiz Notes

7/26/2019 Mechatronics Quiz Notes

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Mechatronics Quiz Notes

Context of Arduino

There are a number of different types of Arduinos to choose from, however, the

most common being the Arduino Uno.

Legacy versions of the Arduino Uno product line consist of the NG, Diecimila, and the

Duemilanove. Key differences from these to the Uno include:

o Use a less powerful chip (ATMEGA168 instead of ATMEGA328)

o Require manual selection of either USB or battery power (and also have a

jumper next to the USB port)

o The NG requires you to hold the rest button on the board for a few seconds

prior to uploading a program.

Features

Relatively cheap

Direct plug straight into a computer’s USB port

Easy to set up

Open source design

The chip on the board plugs straight into your USB port and registers on your

computer as a virtual serial port. This allows you to interface with it as through it

were a serial device.

Built-in voltage regulation (you can connect an external power source of up to 12V

and it will regulate it to both 5V and 3.3V. Can be powered directly off a USB port without any external power.

16mhz clock

32KB of flash memory for storing code

13 digital pins and 6 analogue pins.

ICSP controller for bypassing the USB port and interfacing the Arduino directly as a

serial device.

An on-board LED attached to a digital pin 13 for fast and easy debugging of code

Button to reset the program on the chip.

Arduino IDE

Before you can start doing anything with the Arduino, you need to download and

install the Arduino IDE (integrated development environment).

The Arduino Programmer is based on the Processing IDE and uses a variation of the

C and C++ programming languages.

Plug it in

Connect the Arduino to your computer’s USB port.

The Arduino Uno requires a male USB A to male USB B cable.



Settings

Before you can start doing anything in the Arduino programmer, you must set the

board-type and serial port.

Serial Monitor

Takes data that your Arduino is receiving from sensors and other devices and

displays it in real-time on your computer.

Arduino Blink Tutorial

To build the circuit connect one end of the resistor to Arduino pin 13.

PinMode(13, OUTPUT); initialises pin 13 as an output pin.

DigitalWrite(13, HIGH) turns on the LED (supplying 5V to pin 13).

DigitalWrite(13, LOW) turns off the LED.

Digital Read Serial



LECTURE NOTES

De-bouncing can be done in code (no de-bounce circuit required)

A rotary encoder can transform rotation information to digital (high/low)information

You could make encoders using reed switches and magnets.

The encoder is a sensor attached to a rotating object (such as a wheel or motor) to

measure rotation.

Photo interrupter is connected to two 1K ohm resistors and 5V.

In a theoretically perfect wind turbine, a maximum of 59.3% of the wind’s kinetic

energy can be converted to blade rotational kinetic energy.

Putting an encoder on your turbine shaft allows you to measure tip speed, which can

thus allow you to improve the performance of your WPV.

Wind turbine blades work by generating lift due to their shape. The more curvedsides generate low air pressure while high pressure air pushes on the other side of

the aerofoil.

The net result is a lift force perpendicular to the direction of flow of the air.

The power in the wind is derived by combining the above equations:

o Power = 0.5 x SweptArea x AirDensity x Velocity3 = =1

2 3.

However, the power actually captured by the wind turbine rotor, PR, is a fraction of

the wind power due to the Betz limit and other aerodynamic and mechanical losses.

The coefficient of performance, Cp, of the turbine is expressed as =

.

The tip speed ratio is the ratio of the speed of the turbine tip, at radius R when

rotating omega radians/second, divided by the speed of the wind, v:

o =

=

.

Tip speed is a function of RPM.

Torque, the torque coefficient, Ct, is defined as:

o =

.

Solidity: The total blade area as a fraction of the total swept disc area is called the

‘solidity’. Aerodynamically there is an optimum solidity for a given tip speed and

number of blades.



Multi-bladed “high solidity” rotors run at slow speeds and are somewhat less

efficient than few bladed “low solidity” rotors, but they have much greater starting

torque.

High angle of attack is suitable for higher solidity blade the angle of attack must still

be set carefully. If the angle of attack is too high, the blade creates too much drag – if too low, not

enough lift (rotational force) is generated.

The millis() function returns the number of milliseconds since the Arduino board

began running the current program.

AnalogRead is used to read the outputs of encoder/pushbutton circuits.

EEPROM stores values after power is disconnected.

The mega328 has EEPROM – this memory is kept when the power is off

The mega328 has 512 usable EEPROM addresses.

To pull a pin high, you connect the 3.3V power via a resistor (1K).

To pull a pin low, you can connect the pin to a 1K resistor which is connected to

ground.

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Mechatronics Quiz Notes