Anyone wired up an inline water conductivity sensor to a Picaxe?

J

jsmanson

Member
Hi gang, I am in the process of building a water treatment system for my domestic well (actually, 2 wells). I have a salinity problem in at least one well, and I expect to have to use a reverse osmosis unit to remove the salinity (200-1000 ppm). I expect the salinity levels to vary during the year due to seasonal fluctuating water levels, and I may program the system to switch wells if one well starts to go dry (i.e. brakish), and switch to the other. I have bought the RO unit, and it has a 'pre-treatment' lockout, basically a relay input that will shut down the RO unit if some external process wants to pre-treat the water (or, a picaxe tells the unit to stop...) So what I want to do is automatically sense the conductivity (or TDS) of the inlet water to the RO, and if its over setpoint, route the water through the RO, and if it's under the setpoint, shut down and bypass the RO. Most of that is easy to do with relays and soleniod switches. But I am having difficuly sourceing an fairly inexpensive, inline conductivity sensor that fires out 0-20ma, or 0-5 volts DC, or something that a picaxe can process, calculate and display the measured value, and do the switching around that I have mentioned.

Anyone have any luck interfacing a picaxe to one of the conductivity sensors that I see on ebay? Most of them seem to have proprietary interfaces, along with temperature compensation, as electrical conductivity is sensitive to water temperature...

I bought one of the units below, which measures incoming and outgoing TDS (conductivity), but it doesn't look like I can feed his thing into a Picaxe...

http://www.amazon.com/HM-Digital-DM-1-In-Line-Accuracy/dp/B001EHAZGW

John Manson
 
W

westaust55

Moderator
Can you provide links to datasheet for what you have in mind.
It is hard to tell what may be possible without some real data as the foundation for study/research.
 
M

MPep

Senior Member
A bit of work involved, BUT:

You could tap off the LCD signals. You know they have a common pulsing signal, now use an EXOR gate per segment to check to see if it is ON or OFF. You then make a 7-segment to BCD encoder and feed that into a PICAXE.

Haven't done it myself but I know that the idea works, having seen it in operation.
 
S

SAborn

Senior Member
The item claims to have a micro controller, so if you can track the circuit to the input of the micro, then you should be able to also read the same circuit input with a picaxe, as almost all micros have 10 bit ADC it should make little difference and then you can calibrate the picaxe to the meter.
 
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