The quest for a Home Monitoring System : Part 3

The quest for a Home Monitoring System : Part 3

Sensor Modules for data acquisition

Hardware choices

The initial sensor module was done with an Arduino + DS18B20 sensor and a ENC28J60 ethernet chip. It was pretty fast to build a prototype that would send data via ethernet to a server running a LAMP stack.
However, since I want to have sensors trough out the house (including the exterior), it became a problem since I’m unable to pass an Ethernet cable everywhere I might need a sensor module installed.

The cheapest to add wifi capabilities to an arduino based system would be to add an ESP8622 wifi module :

  • They are low priced  – around 1,7€  a piece on ebay.
  • Answer to AT commands via serial communication (thus an arduino board could simply send AT commands to the module with the data).

But upon more reading,  it was also noted that the ESP8266 could be used as a stand alone module, without the arduino hardware. This helps drive the cost and assembly complexity of each module down further. A major plus was the fact that the arduino IDE can be used with the ESP8266, work with most libraries already included, without changes to software development workflow.

Sensor Module Schematics for version 1.0. Notice the few component count.

And since the ESP8266 supports I2C  and 1 wire data buses, any sensor supporting those protocols can be added to a ESP8266 module.

Sensor module variants

ESP8266 based sensor Modules – PCB version 1 and Breadboard prototypes during code development

A total of 3 variants of the ESP8266 based sensor module, as of 17th February, were built:

  • A module only using a temperature sensor (the DS18B20), with no RTC on board. Exists in breadboard form only and it is currently in use.
  • A module using both a DHT22 humidity and temperature sensor, and also a DS18B20 sensor. Also without RTC support. Module was disassembled and parts used on the PCB version 1.0.
  • A module using a DHT22 humidity and temperature sensor, with a DS1337 RTC, as used on my Nixie Clock. This version was built on a PCB designed in KICAD, and it is currently in use.

Read More

The quest for a Home Monitoring System : Part 2

The quest for a Home Monitoring System : Part 2

Changes to the Home Monitoring System Architecture

Almost a year later, and a working prototype, the development of the monitoring system had reached a standstill, mostly due to the lack of time :

  • On the sensor side , the Arduino + ENC28J60 + DS18B20 combo works, although it is dependent on the availability of a network cable. But the hardware is functional.
  • On the server side , the development of a backend and frontend with the flexibility required (multiple sensor support, dashboard with user selected time intervals, etc)  was starting to take too much time.

Sensor : Arduino + ENC28J60 + DS18B20, Server Side : LAMP stack, chart done with chart.js

So I was faced with a decision regarding the server side of the system:

  • Fully development of a frontend and backend , using a LAMP stack and bootstrap templates. This would take time that I simply don’t have, and the project would probably still be stalled.
  • Or find a solution that would require less effort. And this was only an option when I was introduced to Elasticsearch + kibana stack.

On the hardware side, I had some ESP8622 (ESP-12) modules to try out.

ESP8622 Sensor Module prototype with a DS18B20 temperature sensor

Current Status

Server Side changes

The server side of the Monitoring system was the one that was the most time consuming.

One of the major changes was the replacement of the LAMP stack for elasticsearch and kibana for data storage and  visualization respectively. This removed the need to write a backend and a frontend from scratch. The time that would be spent on writing the back and front ends was spent on the sensor module development (both hardware and software).

Elasticsearch, according to the authors:

” Elasticsearch is an open source distributed, RESTful search and analytics engine capable of solving a growing number of use cases.”

With elasticsearch, the sensor modules sends data in json , instead of sending the data via http get to a php script with the previous Monit System architecture.
And a dashboard with visualizations of the data can be done in minutes.

KIbana Dashboard

Hardware changes

Although the arduino + enc28J60 sensor module was not entirely abandoned, hardware development focus was oriented on the ESP8622 based modules.

The ESP8622 have some interesting advantages over the arduino + ENC28J60 combination :

  • The ESP8622 can be sourced from around  1,7 € a piece (ESP-12) (and it replaces the arduino board and the ENC28J60 in one package)
  • It can be used with the Arduino IDE , and use most of its libraries (no need to learn a new SDK and new tools).
  • No additional network hardware required, since the ESP module is a wifi module first and foremost (DHCP, WPA2 supported out of the box), and thus I could place the sensor module anywhere as long as there is wifi coverage, including the exterior of the house.
  • Less parts per module, since the ESP8622 has an ARM CPU besides the WiFi capabilities : besides the module itself, only the sensor, a RTC (if needed) and some passive components are needed.

However the usage of the bare modules are not as “plug and play” as with arduino boards – additional hardware and wiring required . This is not an issue since the final goal is to have a custom made PCB for the sensor module.


The quest for a Home Monitoring System : Part 1

The quest for a Home Monitoring System : Part 1

General Architecture

For a long , long time I wanted to have a system to monitor, and perform data collection, on my home.
A modular system where I could gather data from indoor and outdoor temperatures to local power consumption.

CasaMonit Initial Architecute proposal

CasaMonit Initial Architecture proposal

The system is meant to be designed in such manner that the server side is fully abstracted from the sensor module side, more sensors modules may be implemented on different hardware platforms. There can be as many sensor modules as required, connected on a single Ethernet network.


Sensor Module Hardware (Prototype)

Prototype Hardware Sensor Module

Prototype Hardware Sensor Module

Read More

My first steps into Film Photography (part 1)


For quite a while, since I began to feel more comfortable with using my DSLR on manual mode,  I had the desire to get into film photography of a while, being pinhole photography the first milestone.

However, for me to deal with film photography, the only practical choices  were 35mm film or 120 film, in regards to availability. My main choice was 120mm due to the fact that the negatives are larger, making it more practical to handle and to make contact prints in the future. The unfortunate side effect is that it is harder to load into the film spiral during film development preparation. And, of course, way less exposures per roll than 35mm film. Another point to consider is camera price. A 120 film camera is, in general, more expensive that a 35mm camera.

Camera Choice

My budget for the camera was set to 120€. In one hand I could get a Holga 120N pretty cheap and call it a day. Lets just say I quickly changed my mind.
The other choice was to get a Twin Lens Reflex (TLR) camera. But due to most if the cameras on my price range being used cameras (and 100% mechanical), I was wary of getting then on ebay, therefore I’ve decided to source the camera locally, at a store that could sell me a clean and tested camera. Unfortunately such stores are 50Km away, in a neighboring town.

Flexaret VII Automat TLR

Flexaret VII Automat TLR

The camera that fulfilled my criteria without looking like a dug up, rusty fossil, or a plastic toy was the flexaret VII automat.
On paper, 1/500 sec maximum shutter speed sounds quite nice, but it also means that the camera uses a more complex leaf shutter design.

Read More


Pinhole Photography Experiments.

After being in a workshop on pinhole photography (held at offo, in Aveiro), and getting a grasp of the development process, it was time to actually start to build a simple camera, as well as to start developing its pictures.

But the initial results were not quite what I expected in terms of sharpness.

Pinhole Photography 1

Photography taken at Aveiro, during the pinhole workshop. This one is quite sharp.

Read More