can open sprinkler run on battery/solar panel

[blinky1986]

Hi
Don’t know much at all about electronics but thought I would have a crack

I have a few specific application where i require a small controller running off either battery’s or solar panel that can be mounted in a valve box (so must be water proof)that can control up to 6 DC 3 wire latch solenoids though the mobile app
Can this be done or am I asking to much
I work in irrigation and a product like this would make my life a lot easier

Thanks

[Ray]

OpenSprinkler is currently designed to work with 24V AC valves only. It’s probably quite difficult to power these valves with battery / solar panel. Technically you need an inverter that converts DC to AC, but I’ve seen discussions that these AC valves can run on DC voltage (al beit less efficient / draws more energy than running on AC).

We have an upcoming product, OpenSprinkler Bee (http://rayshobby.net/cart/osbee-10) designed to be battery powered and work with latching solenoids. The controller will have an RF transceiver which can remotely talk to a main controller that has Ethernet connection. It’s probably also possible to add a bluetooth module to allow phones to directly talk to it. I keep telling people that I am working on it but the truth is that I haven’t made much progress yet 🙁

[gatomon]

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

[Ray]

@Chris: the 24V AC is really only required for sprinkler valves, the Pi itself, runs on 5V DC as you know, so there is a switching converter on OSPi to rectify and step 24V AC down to 5V DC to power RPi. If you have a 12V DC power supply, it’s probably better to step it down to 5V DC directly to power RPi. The reason is that I suspect 12V DC-> 24V AC ->5V DC is inefficient and not a very robust solution especially for WiFi. So what I am suggesting is to split 12V DC into two paths: one goes into the interver to generate 24V AC required by the sprinkler valves; the other goes into a 5V DC step-down converter to power RPi.

Another option, which is probably simpler, is to use 12V DC to directly power everything, including sprinkler solenoids. While most sprinkler valves are designed to work with 24V AC, they CAN operate under 12V DC too (see my blog post here: http://rayshobby.net/?p=9529). If you use this approach, you can feed 12V DC directly to OSPi (OSPi’s switching converter can work with any input voltage between 7V-40V DC). However, you do need to replace the 8 triacs onboard by NPN transistors or N-channel MOSFETs, because triacs will not work with DC current (more technically, they can turn on DC devices but once on they cannot turn them off).

My BS and MS are from UMass and I lived in Amherst for 5 years.

Awesome, I live in Amherst, MA. You can email me directly at [email protected]

[gatomon]

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

[atd_999]

not Ray here …

not sure which hw version you are running, but if you provide 5V regulated,
would the easiest is to remove Fuse F2 and Feed 5V into TP3 base on the schematic below … or which ever one that match your hw ?
https://github.com/rayshobby/opensprinkler/blob/master/OpenSprinkler%20Pi/hardware/ospi_v13_sch.png

Anh

[gatomon]

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.

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