Quo Vadis ? – Page 2 – stories from a home laboratory

Monitoring temperature and humidity

For almost a year I was playing with various temperature sensors and Arduino. Initially the plan was do use some cheap DHT11 sensors in order to measure soil moisture. After running number of tests I found this method not so reliable. Then, I put a number of DHT11 sensors in the house in order to measure temperature and humidity. Out of 10 sensors, only 2-3 were detecting correct temperatures. Then I tried DHT11’s bigger brother DHT22. The results were much better.

The idea for this project was simple and already seen in number of different projects around the Internet:

install a wireless node in every room of the house and collect temperature and humidity,
send this data to the central node (using the same (upgraded) central node described in previous posts),
store data in database,
display data (web page, iPhone notifications).

System overview is displayed in the picture below:

Hacking a weighing scale

Last couple of weekends I mainly spent at home. This was ideal opportunity to do some home maintenance (cleaning 🙁 ). Somewhere under the bed I found a weighing scale that my wife and I occasionally use. This is the simple digital weighing scale from Ikea – GRUNDTAL. During last months I stumbled upon couple of articles about automatic weight logging, so the outcome was obvious: the next home project – wireless logging weighing scale. Luckily I already had necessary tools and parts, so the next couple of days were fun.

The idea was to connect the scale to Arduino Pro Mini, decode the readings from the scale, and send the weight wirelessly, using RFM12B radio module from HopeRF, to the central Homy system. There, the weight with the timestamp would be persisted into the database and published to Facebook wall.

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Homy & Roomba

Roomba has been in our home for some time now. You could even say it a part of the family; it is the liveliest piece of the furniture. We use it for cleaning our apartment and we are pretty happy with it. This cleaning device is a product of iRobot company and the model we have is Roomba 520.

Going around the Internet sites I stumbled upon a nice article about some hardware and software development that includes Roomba – RoombaDecTools. Next thing I dig out was a really nice document that describes technicalities about interfacing Roomba – Roomba Serial Command Interface (SCI) Specification. Everything was clear, a new home project was about to be born 🙂

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Automated irrigation

After successfully monitoring the plants water levels and needs for some period now, it was finally the time to automate the process of watering as well. The idea was to implement a simple drip watering system with one single water source. Each of the three existing plants would be irrigated proportionally, based on its demands. During the period of couple of weeks, all necessary components arrived and the system was ready to be built.

The main part of the system is a water pump. This is a small 300 l/h submergible electric pump. This was good choice because of its low flow and the fact it can be easily put inside the water tank in the corner of the room.

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Homy and plants

After having all the light bulbs in the house under control, I couldn’t resist electrifying the rest of the household 🙂 I spent couple of days looking around the house, and finally found the next “thing” to experiment with. Couple of months ago my wife and me got a Dracaena tree. Since we had no experience in nursing the plants, we had some doubts about when and how often to water it. I decided to solve this problem in geeky engineering way.

After some online investigation on how to measure a “water level” for the plant, I came across some nice articles: How to make a cheap soil moisture sensor?, Gypsum Blocks / Electrical Resistance, Moisture Sensor Prototype, … It was clear I would need to build a gypsum sensors myself, since it was cheaper and more fun. After quick visit to the nearby hobby shop, all necessary tools and materials were at the table: nails, gypsum, thick paper…

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