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Anh,
Thanks for the reply. In fact I’ve already tested a simple solution that works. I do have v1.3 and have studied the diagram you suggested. What I have done, and found works, is to simply cut the lead on pin1 of the LM2596 (the one that provides the input voltage). To get power to the RPi and Ray’s board, I simply wire a “cigarette lighter” to the battery and use a usb charger connected to the micro-usb port on the RPi. This turns on the RPi and the green LED on Ray’s board shines. So far, it works great! I use the PowerStream 12vdc -> 24vac, wired in parellel with the usb device. I connect the output of the PowerStream to the orange connector on the OSPi. I’ve also wired the power to the PowerStream with a 30amp relay that I bought at an auto store. I’m planning to control that relay with the one on the OSPi circuit (haven’t tried that yet, but I don’t expect a problem; the PowerStream could draw 5.1amps and I don’t want to stress the relay on the OSPi). That way, I can turn on the 24vac only when needed (when the sprinklers are running), so as not to drain the battery too much. I’ve ordered a 100W solar panel (get it next Tuesday), and hope to “field test” (literally) next week.
-Chris
BTW, I also installed a 7.5 amp fuse on the plus side of the battery, just in case.
Ray,
Your first idea is exactly what I was hoping to do. In fact, it is easy to get 5v dc from a 12v battery. You can wire a “cigarette lighter” to the battery and plug in a USB charger, then plug a USB charger cable into the Pi micro-usb charging port. The thing I wasn’t sure of was the best way to disable the 24v ac -> 5 v dc part of your circuit. I assume some of your circuits also need the 5v dc. What would be really cool would be if the relay on your board could be used to turn on/off the 24v ac converter, so it only runs when it is needed. I think it’s probably drains the battery pretty fast when it’s on.
What are your thoughts?
-Chris
I’m developing a Hazelnut orchard in Oregon and deploying a drip irrigation system to water each tree. After much work, I’ve decided to use the OpenSprinklerPI box in a distributed system to control the zones. I’m broadcasting a WiFi connection throughout the orchard and talk to the controllers. Each controller support 4 zones which will be turned on and off by the controller. In addition, each zone have a pressure indicator which will inform the controller once the zone pressurizes. There will be a master controller that will communicate with the distributed controllers as well as turning on/off the water pump.
I’ve been researching the use of solar panels, connected to a 12 volt battery, to power the controllers and the values. So far I’ve been experimenting with the “40 Watt 12VDC to 24VAC Pure Sine Wave DC/AC Inverter” from PowerStream (http://www.powerstream.com/inv-12dc-24vac.htm) with limited success. With some fiddling, I can get the Pi to boot and run using wired ethernet. I can run programs in OSPi and turn on and off valve solenoids. One issue seems to relate to the USB port. If I plug a Edimax wifi adaptor into a USB port, it will not run correctly. If the wired ethernet is connected, it will not work with the Edimax plugged into the USB port. I believe the ethernet uses the USB bus and so I suspect there is a power problem related to the required 5 vdc needed for USB.
I’d be more than happy to work with Ray’s hobby to get this to work. I could send you a PowerStream Inverter, for example.
BTW, I have a PhD in Electrical Engineering from Stanford and was a Professor at Cornell for several years. My BS and MS are from UMass and I lived in Amherst for 5 years. I’m also pretty familiar with Debian linux…
-Chris
