home automation with arduino, raspberry using externally powered relay board

Question

I have a plan to put together small home automation system.

For now I was just playing with smaller parts like single type of sensors at once etc... I would like to ask for opinion & check of my scheme if basic idea is ok, before I plug everything together. I saw many variants of externally powered Relay Board, so I am little confused and I am not sure if its ok.

Basic idea is to see data & control everything from website DHT sensors (read and display data on website graphs)

• only DHT22 nr1 will trigger PC-FANs 1 & 2, when temperature or humidity is too high
• PC-FAN (1 & 2): they run ON all the time (set time from ... to ...)
• LED strip (1 & 2): they run ON all the time (set time from ... to ...) (LED strip has to be on separate power line since current A is to high for single relay)
• Soil sensors (1-4) (read and display data on website graphs)
• Water pump (1-4) each separately triggered for period of time when humidity in soil is to low (from Soil sensor 1-4)

Is my plan ok? Any suggestions are welcome, thank you.

small home automation

• st2000: While your presentation looks great, I think the goal here is to ask a specific question and get concise answers. Also, there is an Arduino stack exchange. Regardless, the problem I see is distance limitation... I'll describe this below in the answer so I can give you a link to the c-bus description.

Answer 1

I see a distance limitation problem. USB appears to be the link between the controller and peripherals. That puts about a 5 meter limit on how far away you can place peripherals. There are workarounds to extend USB (search for "usb extender"). But most use longer distance protocols such as C-BUS or RS-485.

In this thread someone posts the link to the people who designed and published C-BUS.

In this thread people are talking about connecting a Raspberry Pi to Arduinos using RS-485 and something called the Modbus library.

• Sebast: Thank you for you answer, so by C-BUS is that mean I2C?
• st2000: You're going to wrong way! I2C, SPI and other similar protocols are meant to be light weight simple ways to communicate between chips on a circuit board. The are meant to go only inches if that. I'm having a hard time finding Arduino C-BUS hardware. So will add links to RS485 to the answer.