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Plant Navigator

Views:4042Difficulty: 3 Status: Development

Light sensors guids this robot towards the light.

Does your bamboo know where its going? Send your hungry plants towards the light so they can photosynthesize some food. Just plop a plant on our light navigator bot and the six light sensors will look for light in all directions. The bot will turn to face the direction with the most light and then drive towards it. Stick a shrub on this robot and see if it finds the sun. Check out our other robots . We consider this bot autonomous , because all the code it uses for navigation is stored on-board in the Atmega168 bot brain.

Images

The PCB

The PCB

Bamboo Looks 4 Light was the original name for the plant navigator.
The Bot

The bots six light sensors detect where the most light is coming from. The bot then turns until it is facing that direction and then it goes. We also put a proximity sensor on there to aviod running into walls.
The Board and the Bot

The populated PCB sits on top of the AA battery pack.

Bamboo Looks 4 Light was the original name for the plant navigator.

Video

Plant Bot Video

Watch the bot at double speed as she follows those high power LEDs!

Code

Light Navigator Code

This is the arduino code that drives the plant navigator bot's little atmega brain. The function:

int minIndex(int a[], int length){  int minIndex = 0;  for (int i = 1; i < numSensors; i++){     if ( a[minIndex] > a[i] ) minIndex = i;  }  return minIndex;}

goes through every one of the 5 light sensors and sees which has the smallest value. The one with the smallest value corresponds to the light sensor receiving the most light. Now depending on which sensor is the minimum there are three possibilities of action. The possibilities are to turn left if the brightest light was to the left, go straight if the bright light was head on, and go to the right if the light was on the right side. This is expressed in the if...else statment below:

 if ( curMin == 0 ){ // go forward we are facing the light     left.write(85);     right.write(105);   } else if ( curMin == 1 || curMin == 2){     left.write(105);     right.write(105);  } else {     left.write(80);     right.write(80 );   }

Download File

/* LucidTronix Plant Navigator * For tutorial, schematics and explantion see: * http://www.lucidtronix.com/tutorials/17 * this servo robot steers in the brightest direction * in effect heading towards the light. * Using five photoresistor light sensors arranged in a circle * And differential steering on the 2 servo motors. */#include const int numSensors = 5;int lightSensors[numSensors];const int ledPin = 13;  Servo left;Servo right;int minIndex(int a[], int length){  int minIndex = 0;  for (int i = 1; i < numSensors; i++){     if ( a[minIndex] > a[i] ) minIndex = i;  }  return minIndex;}void setup() {  Serial.begin(9600);  left.attach(5);  right.attach(6); }void loop() {  for (int i = 0; i < numSensors; i++){    lightSensors[i] = analogRead(i);  }   int curMin = minIndex(lightSensors, numSensors);  if ( curMin == 0 ){ // go forward we are facing the light     left.write(85);     right.write(105);   } else if ( curMin == 1 || curMin == 2){     left.write(105);     right.write(105);  } else {     left.write(80);     right.write(80 );   }}

Parts

parts

Parts

Title	Description	#	Cost	Link	Picture
Servo Motor	Continuous rotation servo motor.	2	$13.95	Link
Servo Wheel	Wheel that attaches easily to servo motors.	2	$4.0	Link
ATMEGA168A-AU	IC MCU AVR 16K FLASH 32TQFPValue:1.8 V ~ 5.5 V 20MHz	1	$2.43	Link
Photocell	Photo resistor Light sensor 16-33KOHMValue: 16 ~ 33 kOhms @ 10 lux	6	$0.8	Link
Crystal	CRYSTAL 16.00000 MHZ 20PF SMDValue:16MHz	1	$0.53	Link
Resistor	RES 10K OHM 1/4W 5% CF MINIValue:10k	10	$0.08	Link

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Permalink: http://lucidtronix.com/tutorials/17

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