[Question on the Plants Watering Watcher circuit]

Audioguru, Thanks again.

If you mixed a level teaspoon of salt ( about 5 grams) in 19 oz ( 454 grams ) of water you had some 11,000 ppm solution.
Your probe is simmilar to the one I use, so your info is very interesting.

I will see if I can overcome the alinearity .......... or live with it.

Best regards, JLB.

[Question on the Plants Watering Watcher circuit]

Sorry, I meant to type CD74HC132.

By the way, do you think that wit the suggested modifications the
circuit will show a linear response respect to the media conductivity?

I plan to measure the conductivity of salts dissolved in water from 0
parts per million to 3000 parts per million.
This is equivalent ( roughly) to a conductivity range of 0 mSiemens/cm to 4 mSiemens/cm.
Will your changes provide a linear response to increased conductivity?
( Twice salt concentration = twice conductivity = twice output from
the circuit ??? ) I plan to rectify the output signal to the LED.

[Question on the Plants Watering Watcher circuit]

Hi there Audioguru:

I was a little bit shocked by the level of controversy that my simple question started.

As a matter of fact I started to look into other circuits as this one
( as it was) had some additional problems like the 10% mark to space
ratio that polarized the probe, and the fact that I need a linear output
as the media conductivity changes.

But with the changes you suggest, including the use of the CD74BC132, I will give it a second try.

Your help has been great !!!!

Don't be surprised if I request your help once again in order to finish my project ( sorry ! )

Best regards, JLB.

[Question on the Plants Watering Watcher circuit]

I have built the Plant Watering Watcher circuit presented under Projects, "science related" circuits and works to a certain extent. Problem is that I find that the LED has only two states ( ON or OFF ), it does not dims gradually as the description states.

As a matter of fact I think that the circuit, as it is, will only put
the LED ON or OFF, as mine does.

I am mistaken ? It really should dim gradually ?
If so, I will really appreciate if you can explain why.

I plan to use it as a conductivity tester for salts disolved in water , in order to measure conductivity in micro Siemens, but not just High or Low. but continuously.

Helpwill be appreciated.
JLB.