dying trees

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As is seasonally traditional, we recently had a dying tree in our house  
the tree had  no roots, the base of the trunk sat in a vesel of water,
and if the water is not kept topped up the tree dies before the end of
festivities.

So I decided to instrument the plastic vessel to confirm water level,

I placed with a couple of strips of copper tape where they are
unobtrusive wired up an NE555 astable to measure the capacitance,  
(R1=2M2 , R210%0k )  I get 12kHz to 18kHz out depending on the water  
level...

So far so good.  


Now I need to convert that to a voltage so I can feed it to some comparator.


 This is what I came up with.
  
  
   +5v  -+-------------+-------.
         |       100nF |       |  PNP
         +-->|--+     ===    ------
         4.7nF  |      |     /e   \
  in   --||-----+-->|--+--+--      +-------+-- out
5Vpk-pk                   |        |       |
                         r1       r2      === 1uF
                          |        |       |
   0v     ----------------+--------+-------+--

R1 offset - 68K
R2 gain - 47K


+5 is from a 7805, diodes are 1N4148

This seems to work pretty well giving me a couple of volts of range.

but am I doing anything dumb there?


before I take this off breadboard (anctually MDF with staples) and make a permanent
circuit on perf board I might increase the capaitors and reduce the resistors to get a lower
impedance..

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Re: dying trees
On Friday, January 12, 2018 at 1:01:18 AM UTC-5, Jasen Betts wrote:
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A frequency to voltage converter?  How about a multivibrator?  

With an AC source you may just be able to measure the water conductivity
to know when it's empty.  Then you just need a rectifier and low pass...

I should try something like that to put in our chlorine dosing tank.  
(We have well water, chlorine dosing takes out the sulfur.)    

George H.  

Re: dying trees
On 01/11/2018 09:32 PM, Jasen Betts wrote:
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All of it.
I just watched Yule Log on TV. Pretty good.

Re: dying trees
terra wrote on 1/12/2018 3:36 PM:
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I'm not sure why a gadget is need to measure the water level.  A live, cut  
tree needs to be topped off every day or even twice a day.  Just set an  
alarm...

--  

Rick C

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Re: dying trees
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I'd rather do it at my convenience, and I'm learning stuff, and
justifying the pile of junk.


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Re: dying trees
On 13/01/2018 6:28 AM, Jasen Betts wrote:
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You can get good results with analogue stuff too, a couple of electrode  
sensor rods joined to a simple transistor switch.

Re: dying trees
On Friday, January 12, 2018 at 6:38:44 PM UTC-5, Rheilly Phoull wrote:
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Can you make an oscillator that turns on with higher resistance?
(I think I know how to do that.)  

George H.  

Re: dying trees
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Make an oscillaor and then short some critical part out with a
variable resistor, you'll probably get frequency and/or waveform
modulation too.  

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Re: dying trees
On Friday, January 12, 2018 at 11:31:34 PM UTC-5, Jasen Betts wrote:
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Well I was thinking of one that turned on when the resistance went up,
I made some probes from SS optical posts.  Worked fine.  I don't  
know what would happen with the system sitting idle (in water)
with DC across the probes.  

 George H.  

Re: dying trees
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Trees don't like copper, so that's why I'm using capacitive
sensing.

I am doing analogue stuff. it'll have a analogue meter on it when I'm
done... (but I'm not going to trim the copper tape to ensure perfect linearity)  
it'll blinkenlights too. maybe a relay in-case I want to slave a pump...  

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Re: dying trees
Jasen Betts wrote on 1/12/2018 10:56 PM:
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I'm pretty sure trees don't like being separated from their roots either.  
I'm just sayin'....

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Rick C

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Re: dying trees
On Friday, January 12, 2018 at 11:01:13 PM UTC-5, Jasen Betts wrote:
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Hmm I think the tree is long past the point where a little  
copper is going to hurt it much more. :^)

George H.
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Re: dying trees
Jasen Betts wrote on 1/12/2018 5:28 PM:
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Do what at your convenience?  Just add the water every day rather than when  
an alarm goes off.  Isn't the tree going to use water at a pretty constant  
rate?

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Rick C

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Re: dying trees
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Water the tree while I'm walking about, not have to interrupt my
activities to service some alarm-clock.

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Another problem is that it's hard (basically impossible) to _see_ how
much water is remaining, and I don't want an overflow. (I can reach in
there with a finger, but then my other hand is supporting myself and I
can't pour...

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It seems to vary,  lots on the first day, and thereafter dependant on
temperature and humidity, this being summer time in a temperate climate  
no attempt is made at climate control other than opening and closing
doors and windows to suit comfort when there's someone home.

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Re: dying trees
Jasen Betts wrote on 1/14/2018 4:21 AM:
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That's what the alarm clock is for, you set it to go off at a time you  
should be free to water the tree, and not have to respond to a dry tree alarm!


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I guess some people see some things as difficult and others see them as  
easy.  I've never had any trouble watering a Christmas tree once a day.

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Rick C

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Re: dying trees

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A point sensor is all you need. That can be done with a couple of
parts, to light an LED when the water level gets low. Of course, that
wouldn't be as much fun as designing a capacitive level gauge.

I've been researching aircraft fuel/oil level sensors lately. They are
usually a rod inside a tube. The outer tube is driven with a KHz range
sine wave, and induces current into the inner rod, proportional to
capacitance hence level. Aircraft fuel has a Dk around 1.7. It varies
some, so the better gages have another wet capacitor in the bottom of
the tank to measure Dk and compensate.

The electronics takes some care to not explode the fuel in the tank.



--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: dying trees
On Sat, 13 Jan 2018 11:42:03 -0800, John Larkin

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A few years back I designed a chip that measured soil moisture
content.  Rather complex... but rather accurate.
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: dying trees
Google

dog water dish auto fill



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Re: dying trees
On Sunday, January 14, 2018 at 10:27:32 AM UTC-5, FreeMan wrote:
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Yeah lotsa level sensing.  My outdoor wood furnace had a magnet
that floated in styrofoam, and turned on the reed relay.  
(styrofoam, or whatever it was, became water logged over the  
years.)

George H.  
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Re: dying trees
George Herold wrote on 1/14/2018 2:34 PM:
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Yes, styrofoam can be closed cell or open cell.  Even closed cell will  
eventually water log.  It should be encased in plastic.

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Rick C

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