John_b
Posts: 2
Joined: Wed Jun 06, 2018 9:35 pm

Simple Auto Watering System (Hardware question)

Wed Jun 06, 2018 9:52 pm

I have a Rpi 3 and my uncle says I can plant all the plants I want on his acreage with the condition I automate the watering process as he is very busy and wont water them for me. I accepted the challenge. He has a large volume water tank that collects rainwater. The plan is to wire everything up and use Java to control the GPIO. Very simply, I will power everything via battery and once per day a motorized valve will open to water the plants and then close.

I ordered this motorized valve earlier today https://m.banggood.com/DC-12V-DN20-CR01 ... s=myorders and looking at the diagram I can only assume SW is switch. My uncle says I could use two relays instead, but what exactly should I use for the switch?

I am a beginner when it comes to electronic hardware of this nature.

wh7qq
Posts: 957
Joined: Thu Oct 09, 2014 2:50 am

Re: Simple Auto Watering System (Hardware question)

Thu Jun 07, 2018 2:07 am

You can purchase battery powered timed valves with hose connections for about the same or much less money as you would have to invest in an RPi/valve/power supply system: https://www.amazon.com/dp/B004INGS8S/re ... =UTF8&th=1. If you have a big hardware store handy, like Home Depot or Lowes, they have the stuff as well. Any good hardware store or garden shop should have it.

Not to discourage you if you really want to learn about computers and wiring things electrical but at your current level of skill, the project you describe may be beyond your means. What you want to do is easily done but requires an RPi or other low power micro-controller, power, uSD card, valve relay(s) and valves plus another computer (or keyboard, mouse and monitor for the RPi) and the knowledge to schedule the RPi to run it all. On the other hand, by all means, get your hands and mind dirty and learn it!
Sent by WH7QQ from an RPi3/Raspbian/pixel desktop.

John_b
Posts: 2
Joined: Wed Jun 06, 2018 9:35 pm

Re: Simple Auto Watering System (Hardware question)

Thu Jun 07, 2018 6:00 am

wh7qq wrote:
Thu Jun 07, 2018 2:07 am
You can purchase battery powered timed valves with hose connections for about the same or much less money as you would have to invest in an RPi/valve/power supply system: https://www.amazon.com/dp/B004INGS8S/re ... =UTF8&th=1. If you have a big hardware store handy, like Home Depot or Lowes, they have the stuff as well. Any good hardware store or garden shop should have it.

Not to discourage you if you really want to learn about computers and wiring things electrical but at your current level of skill, the project you describe may be beyond your means. What you want to do is easily done but requires an RPi or other low power micro-controller, power, uSD card, valve relay(s) and valves plus another computer (or keyboard, mouse and monitor for the RPi) and the knowledge to schedule the RPi to run it all. On the other hand, by all means, get your hands and mind dirty and learn it!
Thank you very much for your response. The challenge would be great and my uncle is an electrical engineer, but he's swamped with work (self employed working 12 hours a day) and most likely would not have the time to help me. If It was a few months ago I would slowly learn but its June 6th already and growing season is now, and my plants are all in small pots ready to be transplanted into way bigger pots. I'll end up buying one of those units you linked, thank you so much.

MarkR
Posts: 126
Joined: Fri Jan 25, 2013 1:55 pm

Re: Simple Auto Watering System (Hardware question)

Wed Jun 13, 2018 5:18 pm

You will probably find that most solenoid valves require several bar of pressure to open. I tried this and I see that they usually require ~ 1bar to open with 12v.

You can't do this easily if you don't have enough head of water, it's better to use a pump instead. 12v submersible pumps are good. The only problem then is that the water may siphon through the pump after it is turned off.

A raspberry pi is neither required nor desirable for such a project; it requires only a simple timer, there are plenty of 12v timers which will switch these loads. A Pi cannot switch the required current and would need at least a transistor + relay, and would also consume a lot of idle power if left constantly powered (more energy than the pump, if the pump only runs a few minutes per day).

I have done this exact project before - and I suggest building an anti-siphon system (easiest is to use a higher reservoir) and use a submersible pump on a time switch, powered by batteries and an off-the shelf time switch. It can all run on 12v.

Also if the system needs to be running constantly in an outdoor location, it is important that it does not contain any obviously attractive items for thieves. No solar panels, or other expensive-looking bits exposed.

MarkR
Posts: 126
Joined: Fri Jan 25, 2013 1:55 pm

Re: Simple Auto Watering System (Hardware question)

Wed Jun 13, 2018 5:21 pm

Update: I looked at the valve on banggood - it looks like it's a motorised valve (not a solenoid) and will not require much pressure to operate, but it will require a controller which can reverse the voltage to turn it on/off. This means more electrics, such as a pair of relays or H-bridge. A pump still seems like a simpler option.

PhatFil
Posts: 209
Joined: Thu Apr 13, 2017 3:55 pm

Re: Simple Auto Watering System (Hardware question)

Wed Jun 13, 2018 5:38 pm

I hate to agree but off the shelf solutions already exist at a lower price point than a basic pi3.. which will involve plugging in batteries and reading a chenglish manual if you go cheapest ;)

imho a better pi project would be to employ some sort of sensors to detect conditions around the 'garden' and log the information regularly, the information saved may prove enlightening when analysing the gardens performance. You could then water in response to actual conditions perhaps

this mod/hack/re-purpose uses cheap bluetooth sensors cost circa £10/15usd and broadcast 4 metrics regarding their environment Light level, temp, soil moisture and soil EC as well as current battery state, tho a single 3v coin cell is expected to last 12month+ https://github.com/ThomDietrich/miflora-mqtt-daemon

while designed for indoor use a jamjar can sit atop one easily enough to keep the rain off.

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