Thursday, 16 April 2015

Pi-based Domestic Electricity Monitor - Part 7 - Project stalled indefinitely.

For now this project has been halted while I work on other things to develop my skills further, especially with databases and web publishing.

Eventually I hope to buy a cheap model A Pi and get this project up and running again.

Thermobot Update

Video of Bot in operation.

The thermobot also stores and plots 24 hours of data. It's finished its job now, but was logging live every minute to a webpage. You can see its results from my conservatory for 16th April 2015 here:

Initially, pyplot was producing a wierd colouring-in effect under the graph, but adding   

to reset pyplot after each plot fixed the problem. I discovered this accidentally.

the updated code to include the data logging and plotting is here:

import RPi.GPIO as GPIO
import time
import matplotlib
import os
import matplotlib.pyplot as plt

#pseudo code:
#   fill a list with 60 zeros
# set the t1_temp variable to 18 deg c
# every minute:
# get the t2_temperature from the chip
# ext:write the temperature to a list or database
# calc the temperatures difference from previous value
# move the bot an amount relative to the temp difference

#initialise bot settings (stepper motor))
enable_pin = 18
coil_A_1_pin = 7
coil_A_2_pin = 8
coil_B_1_pin = 23
coil_B_2_pin = 24
GPIO.setup(enable_pin, GPIO.OUT)
GPIO.setup(coil_A_1_pin, GPIO.OUT)
GPIO.setup(coil_A_2_pin, GPIO.OUT)
GPIO.setup(coil_B_1_pin, GPIO.OUT)
GPIO.setup(coil_B_2_pin, GPIO.OUT)
GPIO.output(enable_pin, 1)
delay = 2

def forward(delay, steps):
 for i in range(0, steps):
  setStep(1, 0, 1, 0)
  setStep(0, 1, 1, 0)
  setStep(0, 1, 0, 1)
  setStep(1, 0, 0, 1)
def backwards(delay, steps):
 for i in range(0, steps):
  setStep(1, 0, 0, 1)
  setStep(0, 1, 0, 1)
  setStep(0, 1, 1, 0)
  setStep(1, 0, 1, 0)
def setStep(w1, w2, w3, w4):
 GPIO.output(coil_A_1_pin, w1)
 GPIO.output(coil_A_2_pin, w2)
 GPIO.output(coil_B_1_pin, w3)
 GPIO.output(coil_B_2_pin, w4)

#load drivers for temperature probe
os.system('modprobe w1-gpio')
os.system('modprobe w1-therm')

temp_sensor = '/sys/bus/w1/devices/28-0414607111ff/w1_slave'

#Get the raw data from the sensor:
def temp_raw():

 f = open(temp_sensor, 'r')
 lines = f.readlines()
 return lines

def read_temp():

 lines = temp_raw()
 while lines[0].strip()[-3:] != 'YES':
  lines = temp_raw()
 temp_output = lines[1].find('t=')

 if temp_output != -1:
  temp_string = lines[1].strip()[temp_output+2:]
  temp_c = float(temp_string) / 1000.0
  return temp_c

#initialise current temperature
currentTemp = 14.00

#make an empty list for 24 hours worth of data
tempLog = [0] * (60*24)

#run the bot
while True:
  oldTemp = currentTemp
  currentTemp = read_temp()
  tempDiff = currentTemp - oldTemp
  if tempDiff >= 0:
   steps = tempDiff * 256
   forward(int(delay) / 1000.0, int(steps)) 
   steps = tempDiff * -256
   backwards(int(delay) / 1000.0, int(steps))

#now do the graph stuff:
#add the new reading to the end of the list 


#delete the first item in the list

  del tempLog[0]

#plot the graph as an image    
  plt.ylabel ('Bedroom Temperature (deg C)')
  plt.xlabel ('Time (minutes) (Full width = 24hrs)')

  plt.ylabel ('Temp (deg C)')
  plt.xlabel ('Time (minutes) last hour')


Pi Science Project: Tank Power - Part 1 - Outline of project

New Project: Tank Power


To establish whether, in the summer, I should heat my hot water tank using electricity via the immersion heater or use gas via the central heating boiler. 

Hypothesis: Electricity is a more efficient way to heat the water in the tank because when using gas, there is heat loss via the pipes transporting the heat from the boiler to the tank and also heat lost from the boiler flue pipe.


Proposed Method:

Use Raspberry Pi and temperature sensor to log the temperature of the tank by fitting the sensor to the outside of the tank. Record the value every 2 minutes. By looking for when the temperature is rising, the length of time for which energy is being supplied to the tank each day can be measured. 

For gas heating, if the quantity of gas used during the same 24hr period is known, the energy consumption can be calculated. 

For electrical heating, if the power consumption of the the heater is known then the energy consumption can be calculated.

Other factors should be revealed, for example the rate of heating for gas compared to electricity and how well the thermostats work at regulating the temperature.

Step 1: Rig up the pi logging the temperature of the tank with the sensor taped to the outside to gather preliminary data. 

draft pseudo code:

#import sqlite to write the temperature and time data to a file
#import matplotlib to write the data  to graphs
#import OS  to access the temperature sensor

#if it doesn't exist create the database
#open the database

#read the current temperature and time

#write time and temp to the end of db

#get the data from the db (how much?)

#1) last 24 hours
#2) last 6 hours
#3) last 3 hours

#plot each graph to a .png for showing on a database

#data analysis extension:
#import last 24 hours data (midnight to midnight)
#read temperature values
#if temperature is rising start the timer
#if temperature is falling stop the timer
#might need to average these values out to allow for small fluctuations
#add the timer value to total 'on' time
#return a value for total time of rising temperature in 24 hrs
#calculate the theoretical value of energy used vs actual?
#for electrical this is easier done by the program if the power rating of the heater is known
#for gas would need to input the meter reading for the 24hour period and do some calcs.