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.