Heating Datalogger

Project to monitorize the heating system of my house. IoT Project.

Motivation

Last year I got heating consumption counting installed. Since I got charged for the amount of water that flow through the counter (whether is hot or cold), I thought: "Hey, let´s stimate when the hot water inside the radiator is acctually getting the air around it warmer"

Specifications

• Low cost
• Electronics
  • USB or 12V power input.
  • Temperature range: 0º - 90º Celsius.
  • Resolution 1º Celsius.
• Open door to fancy things.

First prototype

The objetive of this prototype is to test and workaround some capabilities. To keep things simple the proyect is now divided into two parts:

1. No Internet things:
   • Sensor.
   • Acconditionator.
   • Power supply.
   • ADC.
   • Serial communication.
2. Internet things:
   • Serial communication.
   • SSH, VNC, ...
   • CSV manipulation.

Bottom - Top Architecture.

1. No Internet things

Sensor + Aconditionator + Arduino

Sensor.

As I have laying around some LM35 from previous projects this is going to be the sensor used. From the datasheet:

• Calibrated Directly in Celsius (Centigrade).
• Linear +10mV/°C Scale Factor.
• 0.5°C Ensured Accuracy (at 25°C).
• Rated for Full −55°C to 150°C Range.
• Operates from 4 V to 30 V.

Acconditionator.

• The reference voltage for the sensor will be 4.3V. The reference used is TL431, it has 445,33ppm/ºC deviation for this application.

• The LM358 Op Amp to addapt levels to the ADC. It can be single power supply powered. It´s major downside is the input offset of 2mV. The error in Celsius is 2º. So for this prototype I´ll allow it. But is a big mistake!! The solution would be to use an OP07(75uV input offset) or similar with virtual ground.

Power supply.

The Arduino is powered from a 12V adapter. The aconditionator board could be battery powered sometime so I´ll fix it to 9V with an LM317 or LM7809.

ADC & Serial communication.

I´ll use the basic example sketch AnalogReadvoltage adding a delay to send data through the serial port.

2. Internet things

Just a Raspberry Pi (I´m usign the oldest model): It does the following:

• Load the firmware into the Arduino.
• Read data from the serial port.
• Save data to a CSV file.
• Allow SSH or VNC to debug remotely and send the CSV file anywhere (rigth now my laptop).

What to improve.

Just EVERYTHING. Eventually I want the following:

• One single "brain" such as ESP8266 based board to send data over the "cloud".
• Battery operated.
• Meet specs, obviusly.