plant_sensing experiments as part of project_groworld and hpi

• soil/moisture/light/temperature
• processing/arduino experiments (see: groworld.git)
• variously explored at groworld_tiergarten

from the README.txt

Basic plant sensor kit which currently outputs;

• soil humidity
• light levels
• human presence

Hardware interface based loosly on recollection of Martin Howse's experiements with the Wheatstone Bridge (biosensing) and incorporates parts of a design published by Rob Faludi (moisture circuit) which was in turn based on a design by Forrest Mims, with nods to L. George Lawrence, Botanicalls and the long and tangled path from Jagdish Chandra Bose.

///////////// part of the groworld HPI prototype 
 
#include <stdio.h>
 
#define lightpin 1  // light sensor on analog pin 1
#define temppin 0  // humidity sensor on analog pin 0
#define power 8     // power for sensors
 
unsigned long then = 0; // timer which will run for < 50 days
unsigned long interval = 1; // interval between reads in seconds
 
 
///////////// set up & send
 
void setup()  
{ 
  pinMode(power, OUTPUT);
  pinMode(temppin, INPUT);
  pinMode(lightpin, INPUT);
 
  Serial.begin(9600); 
}
 
 
 
int lightlevel () 
{
  int light = 0;
  light = (analogRead(lightpin)); 
  return light; 
}
 
int templevel () 
{
  int temp = 0;
  temp = (analogRead(temppin)); 
  return temp; 
}
 
 
 
///////////// prints values to serial line
 
char display[64];
 
void loop() 
{ 
    if (millis() - then > interval*1000) {
      then = millis(); 
      sprintf(display, "%u,%u,%u\n", (unsigned int)then, lightlevel(), templevel());
      Serial.print(display);
  }
}
 
/////////////