Suggestions for 3 phase water pump automation

[tharkuri]

Hi,

About me: I am a software guy, have RPi and done some Temperature reading and controlling small relays etc. Not expert in Electrical side, but have patient to listen and will be able to follow instructions.

I am looking for a solution to automate our coconut farm irrigation using OSPi. This is somewhere in a Southern part of India. Please bare with me for this lengthy story as I wanted to paint the complete picture. Here is the illustration of current manual setup.

[attachment=0:2cjsvqf7]Slide1.jpg[/attachment:2cjsvqf7]

Each sub-main line is kept open for certain period (say 1 hour), after that manually open the second line then close the first line. The schedule goes for all 4 lines every day sequentially.
When ever there is a power outage, the 3 phase starter needs a manual restart.

Following are the limitations which I would want to eliminate by this project.
* Our power supply is not consistent, meaning there is no power supply for a certain period of the day, or only 2 phase supply, which is not predictable. There is a person watching the power supply and restart the starter when ever the power comes. Some times we may not have 3 phase supply for the whole day :(.
* We tend to over water or under water our trees very often. Due to this nature of too many human intervention. I am not offered to waste the water or let my trees suffer.

I would really appreciate if Ray or anyone in this forum could suggest an effective solution to automate this setup. Ideally I wanted a comprehensive solution in the following order.

First priority/phase:
1. Replace all manual valves with Solenoid valves(150 meters distance for the 4th valve). Do I need normally Open or Closed? Any specific product?
2. Use OSPi to configure the schedule for 1 hr per valve, accommodate the frequent power outage(not sure how its possible).
3. Use OSPi to switch ON the 3 phase Starter automatically, aligning with the OSPi’s 1 hr schedule for each valve (total ON time will be 4 hrs).

Second phase:
4. Monitor the power line voltage for all three phases, monitor current (amps) – for dry run deduction and log the values into RPi. Use the OSPi’s analog pins.. but not sure what product should I look for to read this info.
5. Use Soil moisture sensor and let OSPi to do the rest automagically 🙂
6. After completing the Phase 1, extend this solution for another farm which is 3 times this size.
7. Monitor the 40 feet open well water level

Any ideas, views most welcome!!. Is it even possible to achieve?

*Have to extend my Wi-Fi access to reach upto this location- saved for another post 🙂
Regards
tharkuri

[scottsh]

I have a few ideas, but I’m a software guy too so there could be better ways to do this. I also only have experience with Dan’s Interval Program written in python – the other programs behave differently.

First, most irrigation systems I use have normally closed valves – this way they shut off when power is lost. I think you want that here, but I see there are some professional irrigation system designs that are normally open. Check out this presentation: http://www.rainbird.com/landscape/resources/webinars/ESPLX-FlowSensing-Mar16-2012.pdf. I don’t think you need any particular product as long as it works on 24v AC.

Second, the Interval Program lets you configure a station to run any amount of time. You do have one interesting requirement in that you might suffer a power outage in the middle of an irrigation session. Currently, the Interval Program only logs when the station is done being watered. This would mean potential over-watering in your case if you lost power in the middle frequently. You’re going to need to modify the software to do something different. I recommend logging during a session on maybe a per-minute interval by creating a log entry and updating it every minute. Also, you’re going to have to modify the code to determine how much watering has been missed and automatically recover.

However, rather than water for 1 hour sessions, you might break that up into maybe 6 sessions of 10 minutes each. It is generally better to let water soak in anyway, and this would let your code use the current logging and overwater at most 10 minutes if power fails during a session.

Third, I think you could use the master valve feature to always turn on the starter before watering. You probably need to have the 24v triac that comes with the OsPi connected to a custom relay to allow it to switch the 3-phase starter on or off.

[Dan in CA]

An interesting project.

You will need to have the OSPi on a battery backup so it will not be effected by power outages. It does not draw a lot of power so that should not be a big problem. Perhaps a small solar panel would help.

I think Scott’s suggestion of running the zones in ten minute intervals is a good idea.

The latest versions of the OSPi boards have analog inputs and a small relay included. The analog inputs could probably be used to monitor power to the pump and the relay could be used to start the pump.

You could write a plugin for the Python program that would monitor elapsed time for each zone and re-schedule irrigation after a power outage based on programmed duration minus elapsed time. The software is designed to make custom features easy to add.

Ray will probably have some interesting suggestions.

Dan

[Ray]

1. Replace all manual valves with Solenoid valves(150 meters distance for the 4th valve). Do I need normally Open or Closed? Any specific product?

Most valves are normally closed (for safety reasons so if power is lost it won’t leave the water flowing).

2. Use OSPi to configure the schedule for 1 hr per valve, accommodate the frequent power outage(not sure how its possible).

As Dan said, you will likely need a backup power supply to keep Pi running. Ultimately you probably want to look at battery-powered controllers with latching solenoid valves — these can be powered by AA batteries and do not rely on power adapter. You can take a look at the OSBee Arduino Shield to get an idea of these types of valves:
http://rayshobby.net/cart/osbeeshield

3. Use OSPi to switch ON the 3 phase Starter automatically, aligning with the OSPi’s 1 hr schedule for each valve (total ON time will be 4 hrs).

If I understand this correctly, this is what a master station can achieve, and master station is already supported in OSPi.

4. Monitor the power line voltage for all three phases, monitor current (amps) – for dry run deduction and log the values into RPi. Use the OSPi’s analog pins.. but not sure what product should I look for to read this info.

This will be a bit tricky because it involves current sensing on the mains. I don’t know much about this.

5. Use Soil moisture sensor and let OSPi to do the rest automagically 🙂

I have been doing research on soil sensor recently. I just wrote a blog post about reverse engineering an off-the-shelf wireless sensor, which may be useful for your application:
http://rayshobby.net/?p=9413

[Dan in CA]

For sensing the 3 phase line you could use something like:
https://www.sparkfun.com/products/11005

Here is some info about measuring 3 phase current:
http://www.electrical4u.com/measurement-of-three-phase-power/

Dan

[Anonymous]

Hi Did you make any progress on this front?! of three phase irrigation?

rgds

[Ray]

There are several different topics discussed in this thread. Which specific topics are you referring to about progress?

[Author]

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