On 01/05/17 13:27, PeterMerchant via dorset wrote:
On 01/05/17 12:26, Terry Coles wrote:
Hi,
I appreciate that many on this list are software oriented, but do we
have any
people with experience of measuring fluid parameters?
The WMT has an ongoing Project to improve the sustainability of water
in the
'Model' River Allen. This follows the route of the real River
through the
Model Town and has, until now, been managed and maintained by
volunteers and
staff turning the mains water tap on and off.
We have mapped out some requirements to do it automatically and a bit
more
sustainably by catching rainwater and pumping it in and out of the
sump at the
bottom of the river system. The current stage of development is that
a bog
garden has been established at the 'source' of the river to clean the
water,
but otherwise the rest is ongoing.
(The Linux dimension will be fulfilled by the use of Raspberry Pi's for
processing and control and for the web-based GUI.)
We have plenty of ideas, but not a lot of practical experience at the
moment.
Our main problem is how to monitor the level of water in a number of
places in
the river system, eg in the water barrels that are storing the
rainwater and
(probably) in the sump. We would also like to measure flow through
the river
system at one or more places.
Obviously we can use electro-mechanical means to do this (float
sensors, paddle
wheels attached to a pickup, etc), but we have been looking at various
electronic methods, such as:
https://www.efxkits.co.uk/liquid-level-sensor-and-types-of-level-sensors/
but commercial sensors tend to be expensive and although I reckon we
could do
the electronics for at least some of those, we have to keep
everything dry.
Has anyone ever done anything like this? Ideally, for level, an
ultrasonic
sensor with a good level of water resistance would be ideal (it won't be
immersed, but it will be exposed to rain, mist etc). The capacitive
sensor
requires RF, which brings it's own issues and the other types may
provide
readings that are too coarse to monitor rate of change of level.
I haven't found anything much yet that will give us flow measurement
in a
'river'. The commercial types tend to be fairly cheap but designed
to go into
pipes. However, we should be able to come up with something using
hall effect
sensors, so I'm more interested in level at the moment.
Any ideas, links to projects that have done this?
1. Many years ago, when my father put a furnace under our house in a
concrete box that was below the lake level, a light bulb on a string
suspended from a microswitch controlled the sump pump. When the water
rose, the bulb floated and switched on the pump. That was simple, and
didn't require a microprocessor, even if they had been invented then.
A dowel, vertically mounted, with a float at the bottom and guides to
keep it in place(eyebolts?). Have a tab on the side that ticks one
Microswitch at top height, and one when it falls to a low. . That's just
straight input to two GPIO on a R-Pi if you insist on being computer
controlled. Otherwise one turns pump on and the other turns it off. KISS.
Peter
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