Calculating the temperature from an Arduino and saving it to tempoDB

arduino_temperature_tempodb.py

import serial
import math
import datetime
from tempodb import Client, DataPoint

# Electronic component constants
POTENTIAL_DIVIDER_RESISTOR = 10000
THERMISTOR_B_VALUE = 3977
THERMISTOR_REF_TEMP = 298.15
THERMISTOR_REF_RESISTANCE = 10000

# Configure the tempoDB client
client = Client('your-api-key', 'your-api-secret')

# Calculates the temperature from the ADC output of the arduino
def calculate_temp(value):
    # Assumes a 5V arduino supply
    voltage = float(value) / 1024 * 5
    # Assumes the thermistor is on the ground side of the potential divider
    resistance = POTENTIAL_DIVIDER_RESISTOR / (5 / voltage - 1)
    temp = 1 / (1/THERMISTOR_REF_TEMP + math.log(resistance / THERMISTOR_REF_RESISTANCE) / THERMISTOR_B_VALUE)
    print "Temperature is: %f K, (%f degC)" % (temp, temp-273.15)
    return temp-273.15

ser = serial.Serial('/dev/tty.usbserial-A800etDk', 9600)
# We want to average the readings over a minute
temperature_array = []
while 1:
    r = ser.readline()
    # Fits the current arduino output line
    split = r.split(": ")
    if split[0] == "sensorValue":
        value = split[1].strip()
        temp = calculate_temp(value)
        temperature_array.append(temp)
        if(len(temperature_array) >= 20):
            mean = sum(temperature_array) / float(len(temperature_array)) 
            print "Saving off this minute's mean: %f" % mean
            # Only save the value when we have an average of 20 points
            client.write_key('temperature', [DataPoint(datetime.datetime.now(), mean)])
            # Reset the array
            temperature_array = []