OpenSprinkler Zone Expansion Board Wireless Communcation

[mschipper]

Hi There,

I am researching using OpenSprinkler at my house and i would like to control sprinklers in my front and back yards. Is there a way to have the main opensprinkler (for use in the backyard) and the OpenSprinkler Zone Expansion Board (for use in the front yard) connect via wireless and have two 24v power packs for power?

Alternatively what is the max length of the OpenSprinkler Zone Expansion Board cable could i run an appropriate 8 core cable around my property?

I’m thinking of either the beaglebone or rpi versions, the main feature i would also like is to have the unit download info from the web to either suspend or enable to watering schedule (i.e. if rain is forcast in the next x days time.)

Thanks,
Mark.

[Ray]

The zone expansion board only consists of a shift register and eight triacs, and does not have a microcontroller or Ethernet controller in it. So it would not be possible to have the main controller talk to expansion board through wireless. You may be able to connected them wired with a RJ45 Ethernet cable (you will need to figure out the wiring). But this hasn’t been tested over a long distance so you may need to experiment with it to see if this is reliable.

[Selenium]

Ray, it’s been a few years – have you gotten any feedback on the longest length of the expansion board extension cable that works reliably? Does 100 feet sound reasonable?

[Ray]

If you are referring to the current version: OpenSprinkler 3.0, the expander uses I2C to communicate with the main controller, so the question is really how far I2C can go. I did some Googling:
http://www.esacademy.com/en/library/technical-articles-and-documents/miscellaneous/i2c-bus/frequently-asked-questions/i2c-faq.html
and it seems going 100 feet is definitely possible, by reducing I2C clock speed.

At the moment, the firmware uses typical fast-mode I2C speed, which is 400kHz:
https://github.com/OpenSprinkler/OpenSprinkler-Firmware/blob/master/SSD1306Display.h#L22
it can be lowered to any clock speed you want (though below a certain number you may also need to modify Arduino’s I2C library because it may be imposing a lower bound on how low the clock goes).

[Author]

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