[chbot] I'm now subscribed!!

Robin Gilks robin at gilks.org
Thu Aug 12 01:13:02 BST 2010

Greetings all

Just catching up on the messages Richard forwarded to me now I've joined
the list.


The valves I use are just about all made by Hunter and I'm using a variety
of 25, 40 and 50mm standard normally closed valves. The small ones run to
about $50 and the larger sizes upwards of $130. The expensive one I have
is a normally open one that is energised to close it - its only a 25mm but
I think they run to about $250 for some reason - I guess they don't
make/sell very many!

You can get them from most of the irrigation suppliers around town - I
started with Water Dynamics next to Placemakers but Hynds @ Hornby is
closer to me and there is a place down Halswell Junction Road that I can
never remember the name of that has a good range of stuff. QuantumGrow at
the back of Sockburn roundabout are good as well - especially for nozzles
etc. PGPW and CRT I've found to be expensive.

Bear in mind I have a few km of pipes buried about the place here - its
definitely industrial scale!

All valves use 24volts AC - run them on DC and they will die in no time!!
The interface to the big pump down the bore hole is also 24volts so that
just takes another channel.

The original 16 channel controller I made used relays to switch the 24v -
each valve takes about 1/4 of an amp but it was just easier to isolate the
supplies that way. I ran out of channels a few months ago so rebuilt the
hardware to use triacs for the switching (much cheaper!!) and upped the
channels to 32.


I think I'm probably a couple of years ahead of you with the interface!!
I'm using a lot of Javascript in the browser that implements an AJAX
interface to the controller. JSON objects are sent back and forth to
control the display and the action of the valves etc.

Since it runs on a wireless router running Linux I have access to all the
facilities of a multitasking operating system - the web server is
multithreaded for example and a lot of things like  timers, filesystem
come for free!!

The interface from the computing hardware to the valve switching is using
a UART to 1-wire chip and all the triacs are driven by 1-wire GPIO
devices. The current monitoring (that checks for open and short circuit
valve) uses a current transformer and a 1-wire chip with an analog input.
All the temperature sensors that are used in the frost protection are also
1-wire devices.

The general idea of the 1-wire interfacing can be seen on my wind turbine
controller - that is released under the GPL and you'll find all the
details on my website @ http://gilks.ath.cx

The irrigation controller I may be commercialising - depends on how I get
on with extending it to handle the tunnel houses. The opposite to frost
protection, there I'll be trying to limit the upper temperature :-)

Robin Gilks

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