[KanyonKris]

I’ve been doing a fair amount of web searching on this topic. Much of the literature is too technical for me. The best I found was this on-line ET calculator:

http://www.tfrec.wsu.edu/orchard/pet/petcalc.html

The Javascript or Java source is available and the author has made a number of helpful simplifications to the Penman equation. 3 of the 4 inputs (average temperature, relative humidity and wind speed) are fairly easy to find on the internet (for example, wunderground.com). But solar radiation is tricky. I’ve found some data for my area, but not for the entire US. The calculator offers an approximation using time of year and sky conditions (clear, partly cloudy, etc.), but I couldn’t find a data source for sky conditions.

Could UV index be used? I searched the web for some correlation but couldn’t find any. It may be possible to compare historical solar radiation and UV index data and look for correlation.

Could we just drop solar radiation? Maybe, but as I vary the solar radiation values it makes a pretty big change to the computed ET. Would ignoring solar radiation produce an unacceptable amount of error (and over/under watering)? I suspect it would but I’m really not sure.

[KanyonKris]

For my irrigation system I’m using a Raspberry Pi and a 4 channel relay board I bought off Amazon for $8.50. The board is made by Sain Smart (http://www.sainsmart.com/arduino-compatibles-1/relay/4-channel-5v-relay-module-for-pic-arm-avr-dsp-arduino-msp430-ttl-logic.html). Sain Smart also makes 2, 8 and 16 relay boards, and boards with solid state relays for more $.

It’s small (75mm x 55mm x 20mm / 2.95″ x 2.17″ x 0.79″), can be driven directly from the Pi, has an LED for each channel that lights when active, and screw terminals for connecting to sprinkler valves.

I connected the relay board to the Pi with a ribbon cable. I bought a 40 conductor ribbon cable ($5 from Amazon – http://www.amazon.com/dupont-cable-200mm-male-female/dp/B00A6SOGC4/ref=pd_sim_pc_6) with individual female connectors on each and peeled of the 6 wires I needed, worked great.

Note that for each relay, the center screw terminal is the common with Normally Closed to the right and Normally Open to the left.

I mounted the Pi and relay board to a plywood board with wood screws, then mounted the plywood board to my garage wall. The Pi uses a USB WiFi adapter to connect to my home WiFi router.

sprinklers_pi needed to be set to Direct Negative for this relay board.

[KanyonKris]

@nhorvath wrote:

I developed my own relay board for the raspberry pi because I had 9 zones and didn’t want to have to use an opensprinklerpi + expansion just for the one extra zone. I posted the design on github in case anyone else wanted to use it: https://github.com/nhorvath/sprinklers_pi/tree/master/hardware/Sprinkler%20Controller

Nice design and I’m impressed you went all the way to making the board yourself.

I hadn’t checked up on Fritzing in a years and didn’t know it can do PCB layout now, very cool.

Just for grins I uploaded the Gerbers to OSHPark to get a quote. $60 for 3 boards.

[KanyonKris]

Version 1.0.6 is installed without issue and is working fine.

Notable user interface improvements:

– On the home page the Zones line now shows the number of enabled zones in a bubble on the right. (Previously it was 15 indicating all possible zones.)

– Names for schedules and zones now support most symbols. Previously if the / were used in a name like “Test/” it would result in “Testtttttttt”

[KanyonKris]

rszimm, I updated the wiki to add your note about how the two adjustments are used together.

Another question, I checked the EventStatus and it shows:

2 Events
00:03:21 2013/9/18 (4)
Event [00] Time:04:00(240) Command 3 data 0,0
Event [01] Time:05:00(300) Command 3 data 0,1

My schedule runs twice. What does the number in parenthesis mean? If it’s run time, is the weather adjustment applied to both times/runs?

[KanyonKris]

I’m not clear on how the Seasonal Adjust in the Settings interacts with the weather based adjustments.

I see in the code you posted on the wiki that weather adjustments start with 100% then add or subtract the 3 weather factors to come up with a percentage between 0 and 200. So if Weather Adjust is enabled for a schedule does it take precedence over the Seasonal Adjust from the Settings page, or are the two used together some how?

Just a thought, should the two adjustments be combined? For example, if Seasonal Adjust is set to 70% then the weather adjustment could take 70 and add or subtract the weather factors to come up with a final aggregate adjustment.

BTW, the github wiki says the humidity adjustment is 1/2% but the formula does 1%. I updated the wiki to say 1% (and expanded the explanation of each of the 3 factors). If you want 1/2%, which seems more appropriate, the code should divide by 4 instead of 2.

[KanyonKris]

Thanks for the 1.0.5 update, installed with no problems, bugs fixed for me.

Feedback: How do I know when the next watering event will be? I know when a zone is running the home page shows a sprinkler graphic with the zone name and time remaining. When nothing is currently running I’d like to see the next scheduled event on the home page. Something like:

“Normal watering” schedule will run tomorrow at 4:15 AM
or
Zone 1 “Front yard” is scheduled to run today at 10:00 PM

[KanyonKris]

Is the real time clock very important?

If the Pi has even a flaky internet connection it will get regular time updates via NTP to keep it’s clock accurate.

One user reported his Pi drifting forward 12 seconds per day without NTP. Could be worse depending on temperature, etc. Let’s say it gains 30 seconds per day, that’s still only 5 minutes every 10 days. I wouldn’t care if my watering drifted that much or more, others may. And I doubt my internet connection would be down that long.

But what if the Pi’s ethernet/WiFi konks out? I may not notice that. An RTC, like the one on the OpenSprinkler board, would help here. Since I’m using relays I better rig up a ping test to alert me when the sprinkler Pi can’t be reached.

Other thoughts / comments?

[KanyonKris]

@nhorvath wrote:

What does the “Interval” setting do on the Schedule page? What do the numbers on the slider refer to?

Interval means how many days between waterings. So 1 would water every day, 2 would water every other day, 3 every 3rd day, etc.

[KanyonKris]

Excellent work!

A minor observation: On the home page the Zones line has a bubble with 15 in it that doesn’t seem to change. It would be nice if this indicated the number of active zones.

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