@RobTX: I will try to cover your questions as much as possible below:
– I have from time to time received questions about the 2-wire system (which includes an encoder on the controller side and decoder at each valve). I honestly don’t have much knowledge about how they work, and most commercial products are closed-source so we don’t know what the encoding scheme is (and it may differ from product to product). Therefore this is not a cost-effective solution. As you said, this can significantly increase the per-zone cost. I don’t think the 2-wire system is common in most residential applications, so we don’t know how big the market is. So unfortunately you are asking for a solution that we don’t have.
– I am reasonably confident that using a Cat6 cable to make an extension cable should work fine for 300 ft. To be sure, you may want to measure the resistance on each wire. As long as the resistance is fairly low, it should be ok.
– We have no plan to make smaller expansion boards. First of all, they are not going to be much cheaper — a 1 zone expansion board is not going to be 1/16 the price of a 16 zone expansion board. Also, creating multiple versions makes it difficult to predict the demand for each version, so it’s harder to prepare stock. For these reasons we do not plan to create smaller expansion boards.
– The current design of expansion boards is that they are to be daisey chained. If you have a particular layout on a graph, you can figure out what’s the best way to connect these expansion boards to minimize the total length of the extension cable.
– We are working on adding support for remote stations in the next firmware. So if you don’t mind having multiple main controllers, this would be a good option, as it will allow you to manage all stations in a central interface, and you don’t have to run long extension cables.
– The design using OSBee Shield is a possible solution, but you will end up writing a lot of code because the demos for OSBee Shield are all pretty rudimentary. One reason I am not actively working on OSBee and making it into a real product is that I haven’t quite figured out the outdoor waterproof enclosure design. Also, if it is going to have WiFi it will definitely need, as you said, solar cell and rechargeable battery. These involve tricky engineering issues that I am not quite ready to tackle.