The active USB hub did not do the trick.

Next steps:
– get some fresh batteries for the sensor ( although it reports to have enough battery power )
– try to relocate the Pi + RFXcom to another room

Controlling things on 433mhz is cool however I also need to be able to rely on the signals to arrive.

I have been experiencing missing sensor values from one of the temperature/humidity sensors (located in the kitchen). I get readings, but I think I miss more of them. I tried to move around the RFXCom a bit but so far this hasn’t improved connectivity.

Since I have my pumps also in the loop I also saw that the ‘off’ signal doesn’t reach the switch once in a while. The distance between RFXCom and this switch is very low (5 meters).

At the moment the RFXCom and a USB wifi adapter are directly connected the USB ports of the raspberry pi. I think the next thing I will try is to get an active USB hub, and see if that improves the situation.

Finally something nice to look at! I have been capturing sensor data from a couple of wireless temperature/humidity sensors (TFA 30.3125) and storing them in mongodb on a raspberry pi. I played around a bit with Rickshaw js to visualize this data.

Since my raspberry pi is not available for the internet ( for now ) I made a screenshot from the humidity to give you an impression

To store all the readings ( 1 temperature + 1 humidity reading per minute ) I used this article on the mongodb blog for inspiration. I have 1 document per day per sensor and the values are stored like this (temperature):


"values": [
{
"0": [{"0": 20200,"1": 20200,"2": 20200,...,"58": 20100,"59": 20100}],
"1": [{"0": 20100,"1": 20100,..."57": 20100,"58": 20100,"59": 20100}],
...
"23":[...]}]


I’m storing the temperature * 1000 because I had problems with floating point numbers on my raspberry pi in mongodb.

TODO: Figure out how to deal with time zones in Rickshaw, it displays the time 1 hour off (luckily we don’t have to get up that early)

The days are getting shorter and the temperatures are falling. For me this means more nerd time (playing around with electronics, node.js, home automation). Last year I have been trying to make some wireless (xbee) temperature sensors and although they are still far from perfect, I want to try something else.

Controlling the pump of my aeroponic system
Last year I bought a couple of relays that are able to switch the 230v mains that we have here in Switzerland. I wanted to use them for turning the pump of my aeroponic chili system on and off. However it is not the 20 milliamps and the max 12volts that we are playing with here, this is serious stuff and I decided to not make this myself.

I actually wanted to stick to xbee/zigbee however it is quite difficult to find zigbee power switches and therefore reverted to 433mhz modules which you can find in almost all diy stores. The good thing about these switches is that there are already loads of people that figured out the signal to send to these switches so all I needed was a little 433mhz transmitter and google guided me to some scripts which with small adjustments gave me what I wanted.

I connected the transmitter to the GPIO pins from my Raspberry Pi and used the 433send script from jer00n to send the on and off signal to the switches. Works like a charm.. (almost).

After moving the switches around in the apartment I realized that the walls made the signal not reliable anymore. Sometimes the switch would respond, sometimes not. Not really an option for the watering system in an aeroponic setup. I found the solution in adding a 17cm piece of wire (antenna) to the transmitter board and now I could even operate switches in the kitchen (highest amount of obstruction between transmitter and switch in my apartment). Sweet!

So I’m now working on writing some scheduler functionality in node.js and a web interface so I can operate the different switches and adjust the schedule.

This morning I installed the JpGraph lib for PHP to create some nice graphs of the readings. Yesterday I managed to create a script which records the readings of the 3 temperature sensors in a database. I first had an interval of 5 minutes but realized that hourly readings should be enough.

[my home-server is a bit slow at the moment so took this graph offline]

 

The first step in my home automation project is logging the temperature on different places in my appartment. The goal is to have small wireless battery powered temperature sensors in every room. These sensors send their data to a base receiver where the data is processed in stored in a database.

I bought some DS18B20 digital temperature sensors and connected them to my arduino board for a test/prototype setup. At the moment I have three of these sensors on the same board, which ofcourse doesn’t make that much sense. But it’s just to play around a bit. The board is still on USB, connected to my Ubuntu server. Every hour, the arduino sends the readings from the sensors to the server.

I now write the readings from the sensors to a log file, but this weekend I want to write the data to a MySQL database.

ai ai ai (as they sometimes say here in swiss german), last post was in June 2010. I think I already opened a lot of posts here with ‘time for an update’. It’s pretty difficult to come up with something interesting every time. But since I have a new hobby project, I think I can update this blog on a more regular basis.

So what’s new? Well, I already had the idea for a long time that when I have a house/appartment it should be stuffed technological gadgets that make the house/appartment into a smart home. Home automation is not so futuristic anymore as it was when I visited the house of the future in the early ninetees. Now 20 years laters, I have my own appartment (well, rental) and I’m very interested in developing my own home automation system.

I’m ofcourse not the only one that has this idea. You can find home automation hobby projects all over te world. There are also a number of commercial systems available. However, I don’t want an off the shelf system, but play around with sensors, microcontrollers and write my own interface.