Some questions

[Archades]

Hi, Just set up my new garden and need to do 6 zones of watering.
I was wondering, can the OSPi do weather monitoring via a hardware temp/humidity and maybe rainfall sensor? We get 5meters of rainfall here per year so sometimes we need to water, sometimes we don’t. We can get months without much rain, and then 300mm in a day type weather.
Can I do datalogging and run it as both an irrigation controller and a weather monitor?

I am thinking of getting these solenoids – Toro 2400mt Richdel http://www.toro.com.au/irrigation/catalogue_product.cfm?prd=408
I will probably be using 7 core 0.5mm2 wire with them as well, would that be sufficient for running 24vAC 0.2amp running, 0.34amp inrush solenoids? 2 of them will be around 30meters from the OSPi so I’m not sure if that wire is thick enough to handle that current without too much voltage drop. I could just run 30m x 2 of poly pipe but less digging to bury the cable. I will only be running low pressure water weeper hoses or drippers.

I am guessing OSPi also has full wifi? Not a fan of running an ethernet cable outside 😛
Thanks.

[Ray]

can the OSPi do weather monitoring via a hardware temp/humidity and maybe rainfall sensor?

The current version of OSPi has a rain sensor terminal and you can connect an off-the-shelf rain sensor to it. These rain sensors are basically rain-activated switches but do not measure the amount of rainfall.

Temp/humidity sensor is possible. You need to wire the sensor to RPi and modify the code suitably.

There are also off-the-shelf rain gauge. I’ve recently looked at a wireless rain gauge and wrote an Arduino program to intercept the signal:
http://rayshobby.net/?p=9056
I haven’t adapted the code to RPi but it should be fairly simple.

Can I do datalogging and run it as both an irrigation controller and a weather monitor?

Dan’s interval program already supports logging and I assume it shouldn’t be difficult to modify it to log weather information as well.

7 core 0.5mm2 wire with them

I am not an expert on this. You can check this page about wire thickness vs. distance you can run:
http://www.hunterindustries.com/support/what-maximum-distance-i-can-run-wire-between-controller-and-valves

I am guessing OSPi also has full wifi?

Yup. Technically it’s Raspberry Pi that has WiFi — you can use a nano-size USB WiFi dongle. That’s a pretty standard addon to Raspberry Pi.

[Archades]

Thanks for the help.

Another question. Are their any flow sensors that people are using that work with this? I’d be curious to know how many litres/day are used even if accuracy is off by 5-10%.

[renoir]

@Archades wrote:

I will probably be using 7 core 0.5mm2 wire with them as well, would that be sufficient for running 24vAC 0.2amp running, 0.34amp inrush solenoids? 2 of them will be around 30meters from the OSPi so I’m not sure if that wire is thick enough to handle that current without too much voltage drop.

To keep voltage drop below 3% at 24VAC, 0.34 amps, cosphi 0.8 and a wire length of 30m, the wire cross-section needs to be at least 0.4mm^2. You’re good.

[Archades]

Just got my opsi, still waiting on my 24vAC PSU. Can I power the rPI via usb and test the RTC feature without the 24vAC or do I just wait till I have the 24VAC and use only that, without usb 5v psu?

[Ray]

Yes, you can power it with USB and test the software features. You just won’t be able to activate any solenoid valve because those require 24V AC power.

[Archades]

When powered by 24VAC there is an AC to DC 5v converter on the OSPI which powers the RPI so I won’t need a 5v usb to the RPI right?

[Ray]

Yup, when you plug in 24V AC, the circuit will output 5V DC to power RPi so you don’t need a separate 5V power source. In fact when you have 24V AC on, you probably shouldn’t use another 5V DC power source, to avoid two regulated sources compete with each other.

[Archades]

Thanks, I’ll give it a test tonight.

Are there any plans for an expansion board that could also allow for sensors? I was thinking a flow sensor at multiple taps, maybe thermometers or soil moisture sensors, etc.

I have 3 main zones for my house, Front, backyard, side of yard. I have 2 pipes going to the front garden, 1 for trees (which I may never use) and 1 for the garden beds (definitely using that). Backyard has 1 for trees, 1 for some veggie gardens which I will use. West Side has 1 for potplants, 1 for garden beds and has it’s own tap and is 30m away from the other tap in the trench I have dug. OSPI will be on the wall about 1-2meters from the tap (in a covered area).

So far I’ll be putting in 7 core .5mm2 wire for the solenoids and running them 30m in that trench, I’ll have 2 solenoids at the West-side tap so that’s 3 of the cores used, was thinking also of using another 3 for the DC positive, negative and signal wire for a flow meter. Not sure though if the AC power will interfere with the signal line on that 30m of cable? Voltage drop over 0.5mm2 for .15A @ 5v looks to be about .3A, so 4.7v would reach the flow meter I guess which hopefully should be enough.

I guess an idea could be an expansion board that uses 24vAC power lines that can run some solenoids, and a data line to send data back to the main OSPI. I would guess it would be 2 wires for AC, and either a built-in AC>DC converter + a common DC ground + signal wire for a total of 4 wires OR have separate AC + DC power inputs + the data line with the DC line having a common ground between the main and expansion?

[Lamby]

@Archades wrote:

Just got my opsi, still waiting on my 24vAC PSU. Can I power the rPI via usb and test the RTC feature without the 24vAC or do I just wait till I have the 24VAC and use only that, without usb 5v psu?

The Toro link you posted was an Australian one – if you are in Aus you can buy a 24vac power supply off the shelf from Jaycar (http://www.jaycar.com.au/productView.asp?ID=MP3032)

[Author]

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