October 26, 2014 at 5:00 pm #34225
I just got my OSPI gear yesterday, and am very pleased with what it can do… I’m hoping to refresh my programming skills and starting to contribute to the group.
I am replacing two controllers (16 zones each) that are spaced about 300 feet apart. I started out thinking that I would just replace them with two OSPI units, but now that I see the expansion modules, I’m wondering if there would be a way that I could just use one controller that would connect to the expansion board via ethernet? I’d rather not run 300 feet of 16 conductor cable. 6 conductor might be a bit more reasonable, but it would be nice to do it via ethernet?
This would make it a lot easier to control the zones, and make it easier for me to get into water flow metering (my first project after I get the controllers in place).October 26, 2014 at 11:27 pm #34230
This question has been brought up quite a few times before. Here are two potential solutions:
Solution 1: Make a custom extension cable using an Ethernet cable or something similar. On OSPi, the extension connector has 8 pins, though 3 of them are all connected to ground (to effectively increase the current capacity of the ground wire). So at the very minimum you need 6 wires (using 1 instead of 3 ground wires). This way you can place the expansion board far away from the OSPi. Keep in mind that you also need the COM wire, which is not part of the zone extension cable.
The downside of Solution 1 is that since the extension cable carries logic-level signals, the resistance on the extension cable over long distance can impact the signal quality, and this may be prone to noise and signal interference.
Solution 2: Use an Ethernet cable or something similar as the solenoid cable (the conductor cable you mentioned). The advantage of this over solution 1 is that the cable does not carry logic signals so it’s less prone to noise and signal interference. However, you will need a lot of wires if you have a large number of stations on the other site. Of course this is based on the assumption that a long Ethernet cable is cheaper than the equivalent number of solenoid wires (which I believe is true).October 27, 2014 at 1:59 am #34234
Thanks, Ray… you and the others have done a great job on this.
I think I’ll just go with two independent controllers for now. Separate wiring would be too much of a hassle. I’m looking at Node-RED and MQTT now, wondering about doing pulling the individual zone decisions into the network, and just sending each controller manual activation messages from the network.
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