Michael Nigbor
Published © GPL3+

HomeEnergy - Pi

Turn a Raspberry Pi into a home energy monitor with inexpensive components.

IntermediateFull instructions provided8 hours12,116
HomeEnergy - Pi

Things used in this project

Hardware components

Raspberry Pi 2 Model B
Raspberry Pi 2 Model B
Newer models should work fine, too
×1
Adafruit ADS1115
×1
SCT-013 Inductive Current Sensor
One is enough to experiment. To monitor both legs of a typical home power panel, you'll need two of these.
×2
GPIO Breakout Board
×1
Resistor 100 ohm
Resistor 100 ohm
×1
Resistor 220 ohm
Resistor 220 ohm
×2
Capacitor 10 µF
Capacitor 10 µF
×2
Prototype Hat for Rasberry Pi
When everything is working on the breakout board, you can transfer it to this soldered prototype board that fits on top of the PI.
×1
PaPiRus HAT Case
Pi Supply PaPiRus HAT Case
A case to put the Pi that's large enough to include the hat. I found several others that would work just as well.
×1

Software apps and online services

Raspberry Pi Raspian

Story

Read more

Schematics

Schematic

This circuit diagram shows how the AC current produced by the sensor is turned into a voltage that can be sampled by the analog-to-digital converter.

Code

Sampler.py

Python
This python routine takes a sample from the ADC and saves it to a database table. The code can also be found in the GIT repository.
# -------------------------------------------------------------------------
# Program: Reads current from ADS115 ADC and saves to database
#
# Copyright (C) 2018 Michael T. Nigbor
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License at https://www.gnu.org/licenses
#    for more details.
# -------------------------------------------------------------------------
import time
import math
import Adafruit_ADS1x15
import sqlite3
import datetime
import array
import json

dt = datetime.datetime.now()
print("===== sampler.py starting at ", dt.isoformat())

#Read configuration
try:
    with open('/home/pi/HomeEnergy/HomeEnergy.json') as json_data:
        config = json.load(json_data)
        print("Configuration read")
except IOError as e:
  print("Unable to open configuration file:", e)
  exit()
    
# Create an ADS1115 ADC (16-bit) instance.
adc = Adafruit_ADS1x15.ADS1115()
GAIN = config["Sampler"]["gain"]

# Polynomial regression coefs to estimate amps
# Based on experiments from 0 to 13 amps
A = config["Sampler"]["A"]
B = config["Sampler"]["B"]
C = config["Sampler"]["C"]

try:
    conn = sqlite3.connect(config["Database"])
    print('Connected to database.')
except Exception as e:
    print("Unable to open database: ", e)
    exit()

values = array.array('l')

n = 0
sum = 0.0
ssq = 0
rms = 0
max = 0
min = 0
amps = 0
values = []

# The inductive sensor returns an AC voltage. Sample at the
# maximum rate for 1 second.  Then calculate the RMS of
# the sampled readings
print("Sampling started.")

try:
    adc.start_adc(0, gain=GAIN, data_rate=860)
    # Sample for one second
    start = time.time()
    while (time.time() - start) <= 1.0:
        # Read the last ADC conversion value and print it out.
        value = float(adc.get_last_result())
        values.append(value)
        if value < min:
            min = value
        if value > max:
            max = value
        n = n + 1
        sum = sum + value
        ssq = ssq + (value*value)
        #print('Channel 0: {0}'.format(value))

    # Stop continuous conversion.
    adc.stop_adc()
    print("Sampling stopped")
except ValueError as e:
    print("ADC configuration error: ", e)
    exit()
except Exception as e:
    print("Unexpected ADC error: ", e)
    exit()
    
# Calculate basic stats on the raw data
avg = float(sum)/float(n)
bias = -avg

variance = float(ssq)/n - avg*avg
stddev = math.sqrt(variance)
ssq = 0.0
sum = 0.0
n = 0

# Refigure sum and sum of squares for "valid" values
# Skipping values more that 3x stddev
for value in values:
    newValue = value + bias
    if abs(value) < avg + 3*stddev:
        ssq = ssq + newValue * newValue
        sum = sum + newValue
        n = n + 1

# Figure the RMS.
if n == 0:
    rms = 0.00
else:
    rms = math.sqrt(float(ssq)/n)
    
print('RMS: {0}'.format(rms))

# Polynomial regression to estimate amps
# Based on experiments from 0 to 13 amps
temp = A + B*rms + C*rms*rms
amps = round(temp, 2)
if amps < 0:
    amps = 0.00
print('Average Reading in Amps: {0}'.format(amps))

#Save to the database
try:
    c = conn.cursor()
    dt = datetime.datetime.now()
    sql = "INSERT INTO currentreading VALUES ( '{0}', '{1}', 0, NULL )".format( dt.isoformat(), amps)
    print( "Saving to database" )
    c.execute(sql)
    conn.commit()
except sqlite3.Error as e:
    print("Error writing to database: ", e)
    exit()
    
conn.close()
print("Database closed")

dt = datetime.datetime.now()
print("===== sampler.py exiting at ", dt.isoformat())

transmitter.py

Python
This Python routine takes records from the database tables and transmits them to a web application. The code can be downloaded from the GIT repository.
# -------------------------------------------------------------------------
# Program: Transmits current readings from a SQLite db to a rest service
#
# Copyright (C) 2018 Michael T. Nigbor
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License at https://www.gnu.org/licenses
#    for more details.
# -------------------------------------------------------------------------
import sys
import time
import math
import sqlite3
import datetime
import array
import requests
import json

dt = datetime.datetime.now()
print("===== transmitter.py starting at ", dt.isoformat())

#Read configuration
try:
  with open('/home/pi/HomeEnergy/HomeEnergy.json') as json_data:
    config = json.load(json_data)
    print("Configuration read")
except IOError as e:
  print("Unable to open configuration file:", e)
  exit()
  
url_login = config["Transmitter"]["loginURL"]
url_reading = config["Transmitter"]["currentURL"]

# Open the database
try:
  conn = sqlite3.connect(config["Database"])
except Exception as e:
  print("Unable to open database: ", e)
  exit()
        
login_data = {
  'username' : config["Transmitter"]["userName"],
  'password' : config["Transmitter"]["password"]
}

# Get a session cookie from the server
try:
  print("Getting access token")
  response = requests.post(url_login, login_data)
  if not response.ok:
    print("Error getting token: ", response.text)
    sys.exit(99)
except requests.exceptions.RequestException as e:  #
    print("Unable to get token: ", e)
    sys.exit()
    
json_data = json.loads(response.text)
tok = json_data["token"]
print( "Token Recieved" )

# Put the token into a cookie dictionary to use in later posts
myCookieDict = {'token': tok}

# Select readings that have not been transmitted yet
try:
  c = conn.cursor()
  dt = datetime.datetime.now()
  sql = "SELECT rowid, * FROM currentreading LIMIT 20"
  rowIDs = []

  c.execute(sql)

  # Loop over the readings, transmit then delete it from the database
  for row in c:
    printableRow = '{0}, {1}, {2}, {3}'.format(row[0], row[1], row[2], row[3])
    reading = {
      'readingdate' : row[1],
      'current1' : row[2],
      'current2' : 0.0
    }
    print( "Posting: " + printableRow)

    #post this row to the cloud service
    r = requests.post(url_reading, data=reading, cookies=myCookieDict)
    if not r.ok:
      print("Error posting data to the server: ", r.text)
      sys.exit(99)

    rowIDs.append( row[0] )

  # Delete these rows
  for rowid in rowIDs:
    sql = "DELETE FROM currentreading WHERE ROWID = '{0}'".format( rowid )
    print(sql)
    c.execute(sql)
    conn.commit()

except Exception as e:
  print("Error processing readings:", e)
  exit()    
  conn.rollback()
finally:
  conn.close()

dt = datetime.datetime.now()
print('===== transmitter.py exiting at ', dt.isoformat())

HomeEnergy-Pi Code

Get the code from this BitBucket Git repository

Adafruit ADS1x15 Python Library

This Python library is used by the Sampler.py script.

HomeEnergy Web Application

Get the web application from this Bitbucket.org repo

Credits

Michael Nigbor

Michael Nigbor

1 project • 6 followers

Comments

Related channels and tags
  • Adafruit
  • Home Automation
  • Pi Supply
  • Raspberry Pi
  • Sustainability