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Published © MIT

Automatic Bike Lights

Hate to remember when to turn on your taillight? This tutorial shows you how to turn your taillight automatically!

IntermediateFull instructions provided1,246
Automatic Bike Lights

Things used in this project

Hardware components

LightBlue Bean
Punch Through LightBlue Bean
×1
Tail light
×1
Resistor 1k ohm
Resistor 1k ohm
×1
1M ohm resistor
×1
0.1uf capacitor
×1
Wire
×1

Hand tools and fabrication machines

Hacksaw
Soldering iron (generic)
Soldering iron (generic)
Screw driver
Needle-nose pliers

Story

Read more

Schematics

taillight-new1.png

Taillight new1

Code

Code

C/C++
/* 
This sketch automizes turning a bike taillight ON and OFF. 

The bike light will turn on when the taillight is in vertical position and it moves.

This example code is in the public domain.
*/

// When acceleration change goes beyond this threshold, the LED will blink.
#define THRESHOLD 100
#define BUTTON_PIN 0
#define LED_STATUS_PIN A0

AccelerationReading previousAccel;
uint16_t ledReading = 0;
bool ledIsOn;
// Timer counts how long the taillight has been still
int timer = 0;
//String state;

void setup() {
// Initial reading
previousAccel = Bean.getAcceleration(); 
}

void loop() {
// Check if the taillight is ON or OFF
ledReading = getLedReading();
if(ledReading == 0){
ledIsOn = false;
}else{
ledIsOn = true;
}

// Get the current acceleration with a conversion of 3.9110-3 g/unit.
AccelerationReading currentAccel = Bean.getAcceleration();

// Find the difference between the current acceleration and that of 200ms ago.
int accelDifference = getAccelDifference(previousAccel, currentAccel);

// Update previousAccel for the next loop. 
previousAccel = currentAccel;

// Check if the conditions are right to turn ON the taillight
if(accelDifference > THRESHOLD// Taillight is moving
&& !ledIsOn // LED is OFF
&& currentAccel.xAxis < -200){// Taillight is in a vertical position
// state = "Active";
timer = 0;
// Turn the LED ON
pressButton(2000);
}
// Check if the conditions are right to turn OFF the taillight
else if(accelDifference < THRESHOLD // Taillight is still && ledIsOn){// LED is ON // state = "Inactive"; timer ++; if(timer > 30){
 // Turn the LED OFF
 timer = 0;
 pressButton(2000);
}
}else{
// state = "Other";
timer = 0;
}

// String output = String();
// output = output + "State: " + state + "\tTimer: " + timer + "\tLED Reading: " + ledReading + "\tAccel Diff: " + accelDifference + "\tAccel X Axis: " + currentAccel.xAxis;
// Serial.println(output);

 Bean.sleep(500);
}

// This function calculates the difference between two acceleration readings
int getAccelDifference(AccelerationReading readingOne, AccelerationReading readingTwo){
int deltaX = abs(readingTwo.xAxis - readingOne.xAxis);
int deltaY = abs(readingTwo.yAxis - readingOne.yAxis);
int deltaZ = abs(readingTwo.zAxis - readingOne.zAxis);
// Return the magnitude
return deltaX + deltaY + deltaZ; 
}

// This function simulates a button press to turn the light ON or OFF
void pressButton(int milliseconds){
// Simulate a button press for a duration 
pinMode(BUTTON_PIN, OUTPUT);
digitalWrite(BUTTON_PIN, LOW);
delay(milliseconds);
// Set BUTTON_PIN as a high impedance input to simulate a "button release" and allow the physical button to function again
pinMode(BUTTON_PIN, INPUT);
}

// We use a low-pass filter connected to LED_STATUS_PIN to monitor the LED state
// When LED_STATUS_PIN is above a certain value it corresponds to the LED being OFF
uint16_t getLedReading(){
uint32_t reading = 0;
// Take the average of 8 readings over a period of time
for(int i = 0; i<8; i++){
reading += analogRead(LED_STATUS_PIN);
Bean.sleep(40);
}
reading = reading/8;
return reading;
}

Credits

Ray Kampmeier

Posted by 11014907 917762441613247 2463536654633089299 o Punch Through

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