LEGO MINDSTORMS & ARDUINOPRACTICAL SESSION 2

Part of SmartProducts

▪ Lego sensors advanced

▪ Driving a two-wheeled robot

▪ Arduino programming basics

▪ Assignment

PRACTICAL SESSION 2

LEGO MINDSTORMS & ARDUINO

6/8/2018AppDev 2slides @ vanslooten.com/appdev

Fjodor van Slooten

W241 (Horst-wing West)

f.vanslooten@utwente.nl

▪ Chaotic

▪ Challenge …for most of you too much work/difficult

▪ 5 groups managed to get it working

▪ We all learned…

6/8/2018AppDev 3

LAST WEEK

Changes today:

Easier building

6 challenges: easy > hard, try to do as many as you can

One extra assistant

If your kit is missing pieces/materials, you

can get replacements from teacher!

6/8/2018AppDev 4

ACCESS EVSHIELD LIBRARY REFERENCE

scroll down until

“EVShieldBank”, click that

Motor… commands?

6/8/2018AppDev 5

EVSHIELD MOTOR COMMANDSACCESS EVSHIELD LIBRARY REFERENCE

Methods of EVSHieldBank

Class, a lot motor-related

This is also available on your own computer:

Documents\Arduino\libraries\EVShield\html\

6/8/2018AppDev 6

EXAMPLESNXT LIGHT SENSOR

6/8/2018AppDev 7

CALCULATE MOTOR DEGREESTO DRIVE A GIVEN DISTANCE

Let’s drive 1m

#define WHEEL_DIAM 4.96 // wheel diameter in cm

double circumference = WHEEL_DIAM * PI; // value of PI is build-in definition

unsigned int distance = 100; // distance to travel in cm

unsigned long degrees = (distance / circumference) * 360;

evshield.bank_a.motorRunDegrees(SH_Motor_Both, SH_Direction_Reverse, SH_Speed_Medium,degrees, SH_Completion_Wait_For, SH_Next_Action_Brake );

Run the motor for

the calculated

amount of degrees Download example evshield_drive_1m.ino

𝑑𝑒𝑔𝑟𝑒𝑒𝑠 =𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒

𝐶𝑤× 360𝐶𝑤 = 𝐷𝑤 × 𝜋

6/8/2018AppDev 8

MAKE 90-DEGREE TURNSPIN WHEELS IN OPPOSITE DIRECTION AT THE SAME TIME

Serial.println("go left");evshield.bank_a.motorRunDegrees(SH_Motor_2, SH_Direction_Forward, SH_Speed_Medium, 254, SH_Completion_Dont_Wait, SH_Next_Action_Float);

evshield.bank_a.motorRunDegrees(SH_Motor_1, SH_Direction_Reverse, SH_Speed_Medium, 254, SH_Completion_Wait_For, SH_Next_Action_Float);

= point turn

swing turn: rotate one wheel and stop (or slow) the other

Important:

commands

should run at

same time!

How? For first

command use

SH_Completion_Dont_Wait

Serial.println("go right");evshield.bank_a.motorRunDegrees(SH_Motor_1, SH_Direction_Forward, SH_Speed_Medium, 254, SH_Completion_Dont_Wait, SH_Next_Action_Float);

evshield.bank_a.motorRunDegrees(SH_Motor_2, SH_Direction_Reverse, SH_Speed_Medium, 254, SH_Completion_Wait_For, SH_Next_Action_Float);

Degrees (in

this example:

254) depends

on wheel

diameter and

trackwidth of

your robot!

See next slide

6/8/2018AppDev 9

CALCULATE DEGREES POINT TURN

𝑅𝑜𝑡 = 𝑛 ×𝑊𝑡

𝐷𝑤

Where

Rot = rotate motor in degrees

n = degree of turn

𝑊𝑡 = track width

𝐷𝑤 = diameter of wheel

Source for calculation

𝑅𝑜𝑡 = 90 ×14

4.96= 254

Make a 90 degrees turn: wheel

diameter=4.96, trackwidth=14:

Tip: try to make a function turn(), similar to

the function driveDistance() in example

evshield_drive_1m.ino

track width

▪ With 3 motors, the EVShield might sometimes behave

strange/appears buggy

▪ Try:

▪ Disconnect all power

▪ Test on batteries only (no USB cable connected)

▪ (temporary) remove all sensors

▪ Switch ports eg. connect motor on M1 > to M2

6/8/2018AppDev 10

EVSHIELD TIPS&TRICKS

6/8/2018AppDev 11

COLOR SENSORS

HiTechnic Color Sensor

NXT Color Sensor

EV3 Light/Color Sensor

Works, read this

info on how to

use it

color = sensor.readColor();

Method readColor() returns color-index, eg.

1 = black, 2 = red …

6/8/2018AppDev 12

ULTRASONIC SENSOR

▪ Uses ultrasonic sound waves to

determine range of object (echo-

location)

▪ Range 5-250cm… or more

▪ Send a ‘ping’… wait for return,

measure time to get distance

NXT-version

cannot be used

with EVShield

EV3 versionBasic Arduino module

#include <NewPing.h>

// define to which pins the sensor is connected:#define TRIGGER_PIN 3#define ECHO_PIN 5#define MAX_DISTANCE 300 // Maximum distance we want to ping for (in centimeters).

//Maximum sensor distance is rated at 400-500cm.

NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); // NewPing setup of pins and maximum distance.

unsigned int distance = sonar.ping_cm(); // read distance from ultrasonic sensorif ( distance > 0 && distance < 30 ) { // is it larger than 0 and smaller than 30 (cm)?

Serial.println("object detected");}

6/8/2018AppDev 13

ULTRASONIC SENSORCODE EXAMPLE

Basic Arduino module

A valid distance

must be > 0

We use the

‘NewPing’ library

EV3 version

See EVShield examples

▪ Motor has build-in rotation sensor

6/8/2018AppDev 14

ROTATION SENSOR

degrees = evshield.bank_a.motorGetEncoderPosition(SH_Motor_1);

Download example evshield_motorGetEncoderPosition.ino

6/8/2018AppDev 15

GYRO SENSOR

See EVShield examples

Gyro Boy, can be build with EV3 kit,which can be borrowed

youtube.com/watch

▪ Combination of detection of angle and acceleration

▪ Can be used to create balancing robots

6/8/2018AppDev 16

ARDUINO PROGRAMMING BASICS

// constants won't change. They're used here to set pin numbers:const int buttonPin = 2; // number of pushbutton pinconst int ledPin = 13; // number of onboard LED pin

// variables will change:int buttonState = 0; // variable for reading pushbutton status

void setup() {// initialize the LED pin as an output:pinMode(ledPin, OUTPUT);// initialize the pushbutton pin as an input:pinMode(buttonPin, INPUT);

}

arduino.cc/en/Tutorial/Button

File > Examples > 02.Digital > Button

6/8/2018AppDev 17

ARDUINO PROGRAMMING BASICS

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);

} else {// turn LED off:digitalWrite(ledPin, LOW);

}}

arduino.cc/en/Tutorial/Button

arduino.cc/en/Tutorial/Debounce

Does not work as expected...?

Check out next example: 'debounce'

▪ Libraries extend functionality

▪ Documents\Arduino\libraries contains folders

with libraries

6/8/2018AppDev 18

USING LIBRARIESMake

programming

easier

Browse through available

libraries (and install it)

Include a library by

selecting one

Add a new library by

selecting its .zip file (you

downloaded)

arduino.cc/en/Main/Libraries

▪ Libraries are nice, as they allow easy programming

▪ But libraries usually use a lot of memory

▪ Combining multiple (large) libraries might result in to much memory

usage

6/8/2018AppDev 19

ARDUINO MEMORY

learn.adafruit.com/memories-of-an-arduino/optimizing-sram

Example: combination of EVShield library and Blynk 'does not fit'

into 1 Arduino

Solution: add an Arduino Nano which acts as a (remote) controller

See few slides further

▪ loop(): check multiple ‘events’

▪ timing of loop()

▪ Look at example given for

spike (spike1.ino)

6/8/2018AppDev 20

BUMPERFile > Examples > EVShield > EVShield_tests > nxt_touch

if (drive && forward) { // if we are driving forward...if (myTouch.isPressed()) { // if we bump into something

// stop and back-upSerial.println("bump");reverseTurn();

}}

▪ Example in pseudo code:

6/8/2018AppDev 21

BUMPED… BACKUP AND TURN

void reverseTurn() {// stopevshield.bank_a.motorStop(SH_Motor_Both, SH_Next_Action_Brake);

// drive backward a littleevshield.bank_a.motorRunUnlimited( SH_Motor_Both, SH_Direction_Forward, SH_Speed_Medium );

// make a 90 degree turnturn(90);

// continue drivingevshield.bank_a.motorRunUnlimited( SH_Motor_Both, SH_Direction_Reverse, SH_Speed_Medium );

}

void reverseTurn() {}

Create a function that

will make the robot go

backwards and turn

▪ Example in pseudo code:

6/8/2018AppDev 22

SEE AN OBSTACLE… FIND A WAY OUT?

void findWay() {// stopevshield.bank_a.motorStop(SH_Motor_Both, SH_Next_Action_Brake);

// look left:// Use evshield.bank_b.motorRunDegrees(…) to turn the motor with the ultrasonic sensor 90 degrees// take a reading of the ultrasonic sensorunsigned int left = sonar.ping_cm(); // read distance from ultrasonic sensor

// look to the right (turn 180 degrees in other direction)// take another readingunsigned int right = sonar.ping_cm(); // read distance from ultrasonic sensor

// rotate the motor back in original position// decide where to go:if (left>right) { // go left

// turn 90 degrees to left}else { // go right

// turn 90 degrees to right}// continue driving

}

void findWay() {}

Create a function that

will find a way out

▪ Tutorial: vanslooten.com/2018/03/17/connect-

esp8266-control-blynk

▪ Wifi: EDUROAM does not work, use a (mobile)

hotspot

6/8/2018AppDev 23

CONNECT TO WIFI

ESP8266 module

Wifi: connect to

“mspot”, password

available

More on this in

next lectures

▪ Control your robot with an App

▪ Robot needs Wifi connection

6/8/2018AppDev 24

BLYNK

blynk.cc

ESP8266 module

More on this in

next lectures

▪ Connect ESP-module directly to Arduino… sadly,

does not work: too much memory usage by libraries

▪ Alternative: add Arduino Nano with ESP-module &

Blynk library > use that as remote controller

6/8/2018AppDev 25

WIFI?ESP8266 module

▪ Follow tutorial until step “Control the LED with Blynk”

▪ Connect power:▪ 5V of Uno > Vin of Nano

▪ 3.3V of Uno > Powerline on breadboard (for ESP8266)

▪ Connect GND

▪ Go (Drive) button:

▪ Add a button to your Blynk App, set to PIN D4

▪ Connect D4 of Nano to D4 of Uno (EVShield)

▪ On Uno if D4 pin is high…:

6/8/2018AppDev 26

REMOTE CONTROL WITH APP

int go = digitalRead(REM_CONTROL_PIN); // read the input pinif ( evshield.getButtonState(BTN_GO) || go==HIGH ) { // start/stop}

▪ Create a vehicle with two driven

wheels (two motors that drive

two wheels) that is capable of

avoiding obstacles

▪ It must be able to drive

measured distances (eg. drive

exactly 2m) and make precise

turns (eg. make a 90 degree

turn around its own axis)

6/8/2018AppDev 27

ASSIGNMENTFOR TODAY’S PRACTICAL SESSION 1/4

Warning: you might want to keep this Lego

model, as we will use it again for

Assignment 4 of Application Development

slides @ vanslooten.com/appdev

This assignment consists of 4 slides:

What vehicle?

You are free to

choose. 2 options

are shown on

next slides

Form groups of 4 again

▪ To speed building, you may want to keep the chassis

of the spike

▪ Add 2 wheels

▪ Make rear wheel of explorer (step 7-9 of this guide)

▪ Add bumper

▪ Add motor on top with ultrasonic sensor

6/8/2018AppDev 28

ASSIGNMENT: LEGO BUILDINGOPTION 1: RE-USE SPIKE CHASSIS 2/4

This assignment consists of 4 slides:

Tutorial for this: “Use Spike chassis to build Explorer robot”

If your kit is missing pieces/materials, you

can get replacements from teacher!

▪ Build Explorer robot from scratch,

eg. from this guide:

nxtprograms.com/explorer

6/8/2018AppDev 29

ASSIGNMENT: LEGO BUILDINGOPTION 2: BUILD EXPLORER 3/4

This assignment consists of 4 slides:

building guide: nxtprograms.com/explorer

If your kit is missing pieces/materials, you

can get replacements from teacher!

1. Make it drive exactly one meter (from given distance, calculate

rotations/degrees to run motor). How accurate is it?

2. Have it make exact 90-degree turns

3. Drive a simple path: e.g. travel 2m forward, make a 90 degree turn,

travel 1m forward

4. Add a bumper: make it reverse & turn when it bumps into something

5. Add an ultrasonic sensor: when it detects an obstacle, find an alternate

direction (for this you will have to mount the sensor to a motor)

6. Add Wifi and control it with your phone

6/8/2018AppDev 30

ASSIGNMENT: CHALLENGESGOAL: REALIZE AS MANY AS YOU CAN, STOP AT 17H

drive 1m

This assignment is a mandatory part of Application Development.

Show at least 3 challenges to receive a ‘pass’.

Only students actually participating will receive a 'pass'.

4/4This assignment consists of 4 slides:

Wifi: connect to

“mspot”, password

available

If your kit is missing pieces/materials, you can get

replacements from teacher!

Form groups of 4 again

Use example on slide

7, you do not have to

program anything!