Garden Watering Timer

[Ziggythewiz]

I'm looking to build a circuit to water my garden automatically. It needs to run off 12v and will power a small water pump. It needs a delay-on adjustable from a few minutes to 30 min, and a delay-off adjustable from 8 to 24 hours. The goal is cheap, simple, and small. Any help would be much appreciated.

 

[HarveyH42]

Maybe 10 years ago, I bought a Rainbird 4 zone controller and a 3/4 inch valve for under $30. Time was in 5 minute increaments. I'd suspect that they are much cheaper, and better features (well maybe not, lot of cheap crap on the market these days...). For building your own, depends on how accurate and reliable you need. Long delays like 8 and 24 hours will take some work. Guessing the 12V is a battery.

 

[Ziggythewiz]

Yeah, it's a battery. The idea is to eventually run it using solar power and a water barrel that I fill once a week or so. Unfortunately, most rainbird and similar products are designed to run straight off a hose connection, and I don't want to have to have that on all the time (it's leaky and noisy). Plus, unless I can find one for under $10, I'd rather just make it so I can have multiple setups in the future.

 

[Hero999]

A microcontroller is the only sensible way of doing something like this if you want to do it yourself.

 

[HarveyH42]

I used a 55 gallon drum to catch the run-off from my roof. A 3/4 PVC male thread is the same as a garden hose. So I put a hole near the bottom of the barrel for the PVC, hooked up the valve. No pump, gravity was good enough. Unfortunately, I never got a good system for screening out leaves and stuff.

Just planted a coffee plant, so might have to hook it back up. I'm not to reliable when it comes to watering plants. Looks like rain, why bother... then no rain.

 

[justDIY]

3/4 npt isn't the same as hose thread - they may be close in diameter, but npt is a finer thread than hose thread. never the less, you can get cheap converters to go from 1/2 or 3/4 (often the same converter) to hose thread.

i tried the rain barrel idea myself, but to get the pressure I need to run my drip emitters, I would have to have the barrels some 15ft off the ground, which isn't very practical.

I'm looking at solar, but the best pressure pump i've seen (with the gph at psi I need) takes ~250watts/hr to run, so if I want two 1 hr watering sessions a day, I'd need to put 500w into a battery. a 100w/hr cell is roughly a grand, and it would need 5 hrs of bright sun a day just to break even. I can buy a lot of electricity from the oil company for a grand.

 

[Ziggythewiz]

Where's the cheapest place to order a microcontroller?

 

[justDIY]

Jameco, possibly Newark or Mouser

 

[Ziggythewiz]

Could this be done just using a 555?

 

[justDIY]

no, the 555 doesn't provide timing for the kinds of duration you're talking about.

however, it could be done with a simple dollar-store lamp timer, they usually have 15 min resolution, and if you get a couple, you can move all the pegs onto a single timer and have lots of on/off events.

 

[Ziggythewiz]

Anyone know where to get something similarly cheap an easy that runs off 12v?

 

[3v0]

Jameco, possibly Newark or Mouser

Just priced the PIC16F88.

Newark is between $1.80 and $2.60 depending on packaging.
Jamco was the about $2 more then Newark.
Mouser was about $1 more the Newark.

Newark runs close to the price at Microchip Direct and has the advantage that you can order things other then PICs.