IoT Home Thermostats – NEST and now connects and logs your home thermostat data!

Your NEST thermostat is likelyWiFi connected. can be authorized by interfacing through NEST to read your thermostat data!

By adding a new Thing, you can link your NEST thermostat and will record your NEST data such as how much you are heating, what the temperature is, what the humidity is, etc.

Potential use cases:

  • Monitor how many hours your furnace has been on so you know when to order more heating fuel
  • Monitor the rate your home loses heat to learn how well insulated your home is
  • Keep a record of the temperature or humidity in your home

Features being added in the future:

  • Connect to Honeywell thermostats
  • Download your data
  • More advanced alerts
  • Advanced temperature control events triggered on any IoT data

Repairing 3D printer heat bed controller

From regular use of the Monoprice Select Mini 3D printer, the heat bed temperature sensor began to fail.  The problem was identified as an issue with the wiring attachment to the heat bed thermistor.

During the repair, the heat bed was removed, and unfortunately, in the process, a short across the heating element and the temperature sensor destroyed the electronics on the mainboard.  The printer still works, but the heat bed temperature always reads 99 degrees Celsius.  The printer starts, tries to print, but heat bead does not heat up.

Possible fixes include:

  1. New printer (,
  2. Warranty replacement,
  3. Mainboard replacement (,
  4. External heat bed temperature controller.

Option 1 is the most expensive, of course, but would guarantee a fix.  Option 2 likely would not work as the issue was caused by actions which voided warranty.  Option 3 is a half-way solution, but the mainboard costs about 1/3 the price of the printer, and ships from China which could take months, and includes risk of rejection at import customs.

Option 4 is quite likely the most interesting solution.  To make it more interesting, why not build a custom controller?  This is what we’ll do.


  • Arduino mini ( which uses the ATmega328 architecture and runs at 3.3V
  • Solu 1.3″ I2c IIC Serial 128×64 White Oled LCD Display Module
  • KY-040 Rotary Encoder Module
  • RFP30N06LE TO-220 Mosfet
  • 10k resistor for power circuit
  • 100K resistor for thermistor circuit
  • 100pF capacitor for thermistor circuit
  • Heat sink (for MOSFET)
  • L78M5 to L78M10 positive voltage regulator.  I used the L78M10 to supply 10V to the Arduino mini voltage regulator, which accepts up to 12V, and regulates to 3.3V.
  • 0.33uF and 0.1uF capacitors for regulator circuit
  • Prototype board and wires for connecting the circuits
  • 100W + power supply.  Need the power to provide enough current for the heating element.

Prototype Version

Below is a picture of the prototype of the controller user interface running.  The firmware is quite simple, and uses a PID circuit to regulate the heating output.


Final Version

The circuit was placed in a more compact form on a soldered board which includes the power regulator, no USB circuit (firmware loaded using a programmer), and the heat-sink.



Print a nice case for the controller and print a nice knob for the rotary encoder.


Prototyping in 3D

Prototyping of components is now underway with the recent purchase of a very inexpensive 3D printer.  The Monoprice Select Mini 3D printer is likely one of the most value for cost printers currently available.  With this new printer, expect to see some rapid progress on developing the first user-ready prototypes of “Things!”


New Online IoT Service in development –

A platform for managing and integrating general IoT systems is being developed.  The website provides a way for users to register and describe their IoT devices.  Using a REST API, data sent to the is logged and managed for users.

Using channels and “Thinkers” a user can trigger various actions and do some basic processing based on the data being sent from the IoT devices.  These can include simple tasks such as sending email alerts, or actually sending messages to other IoT devices to take an action.  A simple example is a thermostat application which turns heating and cooling on and off based on numerous temperature sensors providing input.

Data sent to can also be analyzed using machine learning algorithms in batch mode to develop insights over longer time scales.  One possibility is to use distributed temperature sensors around a house to determine which locations have poorer thermal insulation, or even to measure the thermal insulation value of a home.

The key is that having a general and easy to use platform with a simple user interface allows users to be creative in their use of IoT devices.

Brewing in situ prototype

The first working test version of the real-time connection for a sensor with in situ application is in progress.  This sensor runs sanitized wiring through the air lock which then goes through a waterproof housing into the liquid.


The sensor is connected over wifi which then transmits updates over an IoT backbone.  Currently, it is logging temperature changes into a Google Spreadsheet.


The graph shows an example log from 26 hours.  Not that the temperature fluctuated within a 2 degree Celsius range over this period.

Next steps include adding additional ambient temperature sensors and also to develop the in situ hydrometer sensor.

Base station development progress

The central gateway for the network is the base station.  Now working is a color LCD touch display for the base station, with a WiFi module, and a local radio communications module which connects to the sensor and control networks on the ultra low power wireless network.


In the above figure, at the bottom is the microcontroller (MCU) based on the ESP 8266 system on a chip, which includes 802.11 b/g/n WiFi standards.  The display will show the user interface which is under development and is a touch screen, which enables the user to configure and set options.  To the top right the low power wireless radio is shown, which is used to interface to the local sensor network, and control network.

At this point, the hardware for the base station is basically complete, and the primary work at this point is in further developing the software both on the embedded MCU, for the web-based service, and for the mobile applications.

Temperature and humidity sensor

The new temperature and humidity modules have arrived!


These modules have an on-board 8-bit processor to ensure the readings are calibrated.  They have low power consumption making them ideal for the sensor node application.  They consume 0.3 mA when taking a measurement, but only 60 pico Amps in standby!

Another step closer to putting the sensor node together.  All of the basic parts are now ready, except for the power supply.  Progress is being made on that as well.

Advanced monitoring and control of fermentation

Production of wine and beer has numerous factors influencing the quality of the product.  Best practices are often determined by rule of thumb, or trial and error.  Using modern inexpensive networked sensor systems, a much better method is possible.

some key factors:

  • type of yeast
  • temperature
  • type and amount of sugars
  • rate of fermentation
  • exposure to light
  • sanitation and sterilization

Real-time monitoring of the liquid density and temperature, in combination with temperature control would enable the consistent and repeatable production of high-quality products.  This can now be possible using an immersed sensing system.

Ground moisture sensor

The initial prototyping will involve a two-pronged probe to be inserted into the ground.


This probe works by measuring the resistance of a small current through the soil.  The greater the moisture content, the more conductive the soil will become.  This probe will be placed at the bottom of the solar powered sensor node, which will look like a garden solar light.


Of course, this sensor does not have to be always on, and so it will be important for the wireless node to be able to turn off the sensor between readings in order to conserve power.  The total current draw of this sensor will have to be verified to manage the duty cycle.

Garden monitor for greenhouses

Monitor temperature and humidity in various places within your greenhouse.

Options to include ability to connect to automation for air-circulation, heaters, ventilators.

For heated greenhouses, a single source of heat may not be dispersing throughout the interior, especially when the out-door temperature is low, the heating may not be applied ideally for plants near the edge of the greenhouse.  By installing an automated monitoring system, the entire greenhouse can be configured to optimally distribute heat to all plants by turning heaters and fans on and off as required.