Electric Longboard
Jose Mendoza, Stephanie Lashley, Olivia Robles, Edward Vear
Description¶
This mbed project utilizes bluetooth to control an electric skateboard with an ESC and motor. A uLCD mounted on top of the board displays battery level and velocity in miles per hour using a hall effect sensor. A sonar on the front of the board prevents collisions. A pushbutton on top of the board is pressed by a rider's foot and the board stops if the rider falls off or steps off of the kill switch.
Parts List¶
- 1 FVT 120A ESC
- 1 Turnigy Aerodrive SK3 Brushless Motor
- 1 11.1V LiPo Battery
- 4 AAA Batteries
- 1 Adafruit Bluetooth Module
- 1 mbed LPC1768
- 1 uLCD
- 1 Push Button
- 1 Hall Effect Sensor
- 1 magnet with four pole pairs
- 1 Sonar Module
Schematic¶
Code¶
Bluetooth Motor Control Code
#include "mbed.h"
#include "Servo.h"
#include "rtos.h"
#include "ultrasonic.h"
/// Objects
DigitalIn pb(p22);
Serial blue(p28,p27); // Bluetooh
Servo myservo(p21); // Motor
ultrasonic mu(p6, p7, .1, 1, &dist); //Sonar
Thread t1;
Thread t2;
Mutex off;
bool close=false;
void bluetooth()
{
char bnum = 0;
myservo=0.5;
Thread::wait(2000);
while(1) {
Thread::wait(50);
if (blue.getc() == '!') {
if (blue.getc()=='B') {
bnum = blue.getc();
// Up Arrow
if ((bnum == '5') && (myservo <= 1.0)) {
myservo = myservo + 0.05;
}
// Down Arrow
else if ((bnum == '6') && (myservo >= 0.54)) {
myservo = myservo - 0.05;
}
// Left Arrow
else if (bnum == '7') {
while (myservo > 0.0) {
if (myservo < 0.05)
myservo = 0.0;
else
myservo = myservo - 0.005; // Brake
}
}
// Right Arrow
else if (bnum == '8') {
myservo = 0.5; // Neutral
}
}
}
}
}// ends bluetooh
void dist(int distance)
{
//put code here to execute when the distance has changed
if(distance<400) {
close=true;
}
}
void stop()
{
while (myservo > 0.0) {
if (myservo < 0.05)
myservo = 0.0;
else
myservo = myservo - 0.008; // Brake
}
}//ends stop
int main()
{
pb.mode(PullUp);
myservo = 0.0;
wait(0.5); //detects signal
//Required ESC Calibration/Arming sequence
//sends longest and shortest PWM pulse to learn and arm at power on
myservo = 1.0; //send longest PWM
wait(8);
myservo = 0.0; //send shortest PWM
wait(8);
//ESC now operational using standard servo PWM signals
t1.start(bluetooth);
mu.startUpdates();
while (true) {
if(close) {
t2.start(stop);
Thread::wait(1000);
close=false;
}
mu.checkDistance();
}//ends While
}// ends Main
Display Code
#include "mbed.h"
#include "uLCD_4DGL.h"
#include "rtos.h"
Ticker t;
InterruptIn risingEdge(p8); //halleffect sensor
uLCD_4DGL uLCD(p9,p10,p11); // serial tx, serial rx, reset pin;
AnalogIn batt(p19);
volatile int count = 0.0;
volatile float vel = 0.0;
float pbatt = 0.0;
void pulses() //hall effect triggers
{
count++;
}
void halleffect() //calculates velocity
{
float temp = count; // Copy count
count = 0; // Reset the count for next second
temp = temp/4; // four magnets in trigger - gives rps
vel = temp * 3.14159 * 0.035 * 2 *60 * 60 * 0.000621371 ; // radius of .035m
}
void display(void const *argument) //update battery voltage display and velocity
{
while(1)
{
float battAdj = float(batt * 3.3 * 3.968);
uLCD.color(WHITE);
uLCD.locate(2,2);
uLCD.printf("%3.1f", vel*0.67);
uLCD.locate(2,3);
uLCD.printf("MPH");
if (battAdj >= 11) {
uLCD.filled_rectangle(6,99,29,16,GREEN);
pbatt = battAdj;
}
else if ((battAdj >= 9)&&(battAdj < 11)) {
uLCD.filled_rectangle(6,99,29,16,WHITE);
uLCD.filled_rectangle(6,99,29,45,(GREEN+RED));
pbatt = battAdj;
}
else if (battAdj < 9) {
uLCD.filled_rectangle(6,99,29,16,WHITE);
uLCD.filled_rectangle(6,99,29,70,RED);
pbatt = battAdj;
}
Thread::wait(1000); // Refresh after one second
}
}
int main()
{
uLCD.cls();
uLCD.baudrate(3000000); //jack up baud rate to max
uLCD.background_color(BLACK);
uLCD.cls();
uLCD.text_width(3.5);
uLCD.text_height(3.5);
uLCD.filled_rectangle(5,100,30,15,WHITE);
uLCD.filled_rectangle(12,15,22,10,WHITE);
risingEdge.rise(&pulses); //interrupt routine
t.attach(&halleffect, 1.0); //calculate velocity every second
Thread displaythread(display); //update display
}
Photos¶
Top View of the Board
Underside of the Board
Demo Videos¶
Overall Demo
Sonar Demo