SparkFun Forums

[nikolaj]

I am looking to build a low power (battery powered, with recharge eventually through wind or solar) automatic plant watering system of size suitable for my girlfriend's balcony (basically a couple tubs of tomatoes, basil, and flowers). I plan to use the two-nail system to hook up moisture detection so i can make this all as automatic as possible.

That being said, I am having alot of trouble finding a low cost/low power dc water pump. I have seen all sorts of ideas, from windshield washer pumps (too much current), to aquarium air pumps (mostly AC), to the sensidyne micro air pump AA (can't find a supplier). GPH is not so critical, and i only have to pump a trickle about 2ft up. I once bought a super cheap science project mabuchi motor powered pump from edmund scientific that i was hoping to find, but that seems to have vanished from the net (google).

Any ideas?

[olivier_p]

Hi,

Wouldn't you be better off hooking your system on running water and look for a DC valve? I am thinking of something that looks more like a lawn watering system and is hooked on a garden hose. That way it will take a lot less power to activate a solenoid valve rather than a water pump.

Tell me what you think!

[bigglez]

Greetings (No First Name Supplied),

I am looking to build a low power (battery powered, with recharge eventually through wind or solar) automatic plant watering system of size suitable for my girlfriend's balcony (basically a couple tubs of tomatoes, basil, and flowers).
....
Any ideas?

I assume this is a self-contained system with a cistern
(tank or bucket) to hold the water? (Or, is it fed from
utility water through a pipe or hose?).

Have you considered gravity feed? You would only need
a controlled water valve.

Another technique would be to seal the water tank and
feed compressed air into it to force the water out.
You can store compressed air in another tank, and use
a controlled air valve.

Comments Welcome!

[riden]

Like Peter, I was thinking gravity feed with a value. The other thing that comes to mind is hacking one of those $9.95 USD battery powered virtual aquariums. They have a battery powered (3-5v) impeller and it might get you two feet of rise.

[leon_heller]

An aquarium air pump would probably pump water OK, I think they have a diaphragm pump. They operate off low voltage so could be easily controlled. They are a bit noisy, though.

A gravity feed might be better, as has been mentioned.

Leon

[nikolaj]

The problem is that my girlfriend's balcony does not have a power outlet or running water, so that gets rid of the A/C pump and running water feed. I plan on having a bucket, and eventually minimize my interaction to keeping the bucket above a certain line.

I considered the gravity fed system, but there is limited space to put a raised bucket above the tubs (which are at banister-level to optimize sun), especially to make it very accessible.

If i were to go for a gravity system, what kind of valve should i look for? I have looked around, and am not sure where to go for low power, inexpensive electronically controlled water valves (is there a homebrew recipe for this?).

Noisiness isn't a huge issue as i imagine this will only run a moisture check and pour water 1-2 times a day for a minute or so.

Thanks for all the great replies!

[bigglez]

Greetings (Still No First Name Supplied),

If i were to go for a gravity system, what kind of valve should i look for? I have looked around, and am not sure where to go for low power, inexpensive electronically controlled water valves (is there a homebrew recipe for this?).

You may have a couple of ways to solve this part
of your project. Firstly, if you have access to a
surplus store (for electronics and factory equipment)
you can find some very high quality values that are
designed for factory automation and in particular
semiconductor cleanroom applications. A $100ish
stainless steel electric valve can be had for five bucks!

Secondly, at your local home improvement place
you should find a wide selection of brass fittings for
air/gas or water, and poly tubing in various sizes,
including simple shut-off valves.

I doubt you'll find an electric valve, but you can
adapt a manual one to work from an R/C servo.

Comments Welcome!

[nikolaj]

The R/C servo sounds interesting, i have a few kicking around. Of course this is still the suboptimal gravity fed system, but might be a good starting point (there are tons of drip irrigation supplies floating around San Diego, where I am).

bigglez - I am lucky enough to have a rare-enough name on an English language board to have it be my username: Nikolaj. :)

[lyndon]

You can find battery powered (DC) aquarium pumps in most pet stores. I have one around here somewhere. Cost is about $10 or so.

[emf]

There are a bunch of solar powered fountain kits out there which use 6V or 12V pumps. You could just buy a replacement pump, which should be in the $15-20 range. Kits with a pump, battery, and solar cell are $45 and up.

[nikolaj]

I found solar cells and a "solar water pump" (low power pump i am guessing) at http://kelvin.com, and ordered. Pumps are $10. Prices seem reasonable. I will report back when I get them.

[nikolaj]

So i got my cells and pump and have been playing around with possible circuits. The pumps are all-right, although new requirements (gf wants to water hanging spider plants!) might require higher power pumps in the future.

Anywy, I would like to power the pump off some old camera batteries, as they are li-ion, and the camera is defunct. The batteries are 3.7v, and the solar cells i have are 0.5v, 1A . From googling, I see that a trickle charge would be best, so i have to drop that amperage (no biggie). What worries me is I am wondering if having 1.5v from the solar cells will charge the 3.7v batteries (hooked up in series with the batteries).

Also, if I want to power a 12v windshield washer pump for the high up plants, how would i transform the 3.7v to 12v (or do I just need a bigger battery, which reinforces my earlier question about 1.5v solar cells charging 12v battery).

Thx to those who have responded so far!

[Philba]

A lot depends on your batteries as well as the loaded current draw of your pump. If you need to generate 4 to 5 feet of head, it's probably going to take some current. You should measure what it takes in a realistic setting.

To answer your question directly, you will need a boost switcher. National web bench will give you a complete design, just specify your input and output voltages plus output current. http://www.national.com/analog

However, instead of camera batteries, I'd suggest you get a smallish 12V gel cell battery. Charging is a lot simpler and they have a lot more capacity. No need for a boost circuit.

[nikolaj]

Hm, I think you have convinced me on the larger battery. I guess the other part of my question (forgive my noobness), is can I recharge a 12V gel battery with 1.5v coming from solar cells? Any place I can look for very simplified example circuits (I was thinking I would put the cells in parallel with the battery and my uc/pump circuits).

Thanks again for all the help!

[Philba]

no, you will need >12V to recharge a 12V battery.