The idea is that we wish to control mains power devices using the GPIO (General Purpose Input/Output) pins on the Raspberry Pi. We would like to do this without using anything that involves wiring 240V AC (Opto-relays are available for those who wish to do this, but we want something that’s safe enough for everyone to use).

The kit used here use microwave senders and receivers to send packet trains which tell our mains plugs to switch on and off. The plugs have built in receivers and a remote control is usually used to switch the plugs on or off. We want to use the Pi to do the work.

Using Mains control plugs from dbtech 25 UKP for 5 from Amazon.co.uk. I wouldn’t necessarily recommend using the dbtech plugs. I’ve had two plugs go bad on me (stuck relays). I would recommend using the Homeeasy plugs instead which have a definite on/off state and appear to be of a better build quality: http://www.amazon.co.uk/Home-Remote-Control-Socket-Silver/dp/B003EGMFA0

Here is my code to control them using the same codes as the remote: http://reversemidastouch.com/code/homeeasy.zip Git Hub code

and 25 UKP circuit boards from Noisepower: http://noisepower.co.uk/mains-control-raspberry-pi/

Direct from Noisepower: http://noisepower.co.uk/downloads/

If you want tng’s modifications to the code (list out the 1’s and zeros) http://reversemidastouch.com/code/NOISEPOWER.zip Git Hub code

tng’s main C program for toggling the dbtech is 1_on.c

sudo apt-get install gcc make

Download the Broadcom bcm2835 library, build and install it.

gcc -o toggle -l rt ./1_on.c -l bcm2835

The executable takes two arguments:

• A set number (0..15) which is unique to the set of plugs you have ordered.
• A plug number which is stamped on them (1..5).

Up to 80 plugs can be controlled from one board!

root@raspberrypi:/usr/local/bin# ./toggle 13 1
fixed is 1746944
x is 29009926
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110
1101110101010100000000110

(Sends a 25 bit string 16 times), which set 13, plug 1 recognises as it’s toggle code. The same string is repeated to help ensure that the signal is detected.

root@raspberrypi:/usr/local/bin# ./toggle 13 5
fixed is 1746944
x is 29011456
1101110101010111000000000
1101110101010111000000000

root@raspberrypi:/usr/local/bin# ./toggle 13 4
fixed is 1746944
x is 29010304
1101110101010100110000000
1101110101010100110000000

root@raspberrypi:/usr/local/bin# ./toggle 12 4
fixed is 1746944
x is 26913152
1100110101010100110000000
1100110101010100110000000

root@raspberrypi:/usr/local/bin# ./toggle 1 1
fixed is 1746944
x is 3844102
0001110101010100000000110
0001110101010100000000110

As can be seen, the first 4 bits determine the set number and the last 11 bits (the very last bit is not used) control the plug number.

Code available from tng, but deployment is outside the scope of this talk: http://reversemidastouch.com/code/django_plugsocket.zip

The Noisepower circuits use the 433MHz transmitters from cool-components.co.uk @ 2.75UKP http://www.coolcomponents.co.uk/catalog/link-transmitter-434mhz-p-810.html

The same codes as for switching the Noisepower board can be used, but the timings of the ones and zeros need playing with. I would recommend the Noisepower board as it’s simple to use and produces a nice clean signal. I would also recommend getting an oscilloscope or having lots of patience with Audacity and a line-in.

433MHz receiver@ 3.30UKP http://www.coolcomponents.co.uk/catalog/link-receiver-4800bps-434mhz-p-867.html

On a traditional PC – with a line-in port.

# sudo apt-get install audacity

Run audacity, record from the line-in. Note that plugging into the Mic socket may destroy your PC/Sound card.

Zoom in using the spyglass on one of remote control presses:

A long up period followed by a short down period corresponds to a 1.

A short up period follwed by a long down period corresponds to a 0.

This translates to:

1101110101010100000000110

Which corresponds to our 13:1 Set:Plug. Wahey! Happy days. This could be handy…..

Homeeasy plugs:

http://reversemidastouch.com/code/homeeasy.zip Each plug has an On and an Off state. My plugs look like this:

1ON =  1gap22213131232221312231313123 213 2221
1OFF = 1gap22213131232221312231313123 222 2221
2ON =  1gap22213131232221312231313123 213 2212
2OFF = 1gap22213131232221312231313123 222 2212
3ON =  1gap22213131232221312231313123 213 2131
3OFF = 1gap22213131232221312231313123 222 2131

433MHz, 315MHz and 868MHz are used for loads of home automation hardware – having learned how to sniff packets, it is possible to control central heating boilers, light switches. UPDATE: 30-Sep-2013. I got the boiler on /off codes working:

http://reversemidastouch.blogspot.co.uk/2013/09/work-in-progress-controlling.html

All the code here and for controlling boilers is now in github:

https://github.com/tommybobbins/Raspi_433

Loads more exciting possibilities exist: http://jeelabs.org/ 315MHz receiver http://www.coolcomponents.co.uk/catalog/link-receiver-4800bps-315mhz-p-901.html

868MHz: http://jeelabs.com/products/rfm12b