[chbot] Wanting to get in touch with Robin (or anyone else who has implemented a controlled irrigation system)

Robin Gilks robin at gilks.org
Thu Aug 12 11:08:39 BST 2010

> Considering the high cost of "industrial" solenoids + the need for
> providing
> and switching 24AC etc, I would seriously consider hacking one of those
> electronic timer type values that you can buy at any hardware shop. I have
> a
> two channel unit that I bought from Bunnings for $50 or so.
> These have a motor + gearing inside that drives the valve open or closed
> as
> needed. Works from 3V.
> This approach would be under powered for irrigation of a large orchard
> etc,
> but it would be fine for the smaller set-up. If power fails then they stay
> open. However power is probably not a big concern since a couple of AA
> cells
> would power this + micro for well over a year.

Must admit to installing all the valve gear before I thought about
designing and building my own controller - I just used toggle switches in
the pump shed for 2 years. That changed because 2 years ago I lost a few
$$$ worth of walnut trees in a bad frost and the commercial controller I'd
bought (but hadn't installed) couldn't handle temperature inputs.

Now I've got all the basics its easy enough to extend so with the current
code I can set up arbitrary groups (all tunnel houses, all veg plots, all
treeline drippers etc).

The biggest problem I had to overcome was being able to select all the
walnut trees but the pump can only handle 2 sections at a time out of 5 -
160 sprinklers at 80l/s. I already only triggered the well pump if the
demand was high enough (so the veg plots can be watered from the domestic
pump) so I defined the max delivery from the pump and used an algorithm
that would maximise its use whilst ensuring that 2 does go into 5 an
integer number of times. In fact it goes round the 5 sections twice for
half the time period - took me ages to get the code right!! It can cope
with any combination now (even 3 or 4 at a time out of 5). The solution
the code produces is now: (1,2) (3,4) (5,1) (2,3) (4,5)

This also means that if I set 1 hour of watering the system runs for 2.5
hours to get round it all. One of the reasons I'm extending the codebase
to implement statistics!

Anyone want to buy a very nice unused 12 channel Hunter ICC controller :-)

Robin Gilks

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