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dying trees

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 , R2=100k ) 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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Reply to
Jasen Betts
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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.

Reply to
George Herold

All of it. I just watched Yule Log on TV. Pretty good.

Reply to
terra

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...

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Rick C 

Viewed the eclipse at Wintercrest Farms, 
on the centerline of totality since 1998
Reply to
rickman

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

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Reply to
Jasen Betts

You can get good results with analogue stuff too, a couple of electrode sensor rods joined to a simple transistor switch.

Reply to
Rheilly Phoull

Can you make an oscillator that turns on with higher resistance? (I think I know how to do that.)

George H.

Reply to
George Herold

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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Reply to
Jasen Betts

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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Reply to
Jasen Betts

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 

Viewed the eclipse at Wintercrest Farms, 
on the centerline of totality since 1998
Reply to
rickman

I'm pretty sure trees don't like being separated from their roots either. I'm just sayin'....

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Rick C 

Viewed the eclipse at Wintercrest Farms, 
on the centerline of totality since 1998
Reply to
rickman

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.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin

A few years back I designed a chip that measured soil moisture content. Rather complex... but rather accurate. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
     It's what you learn, after you know it all, that counts.
Reply to
Jim Thompson

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.

Reply to
George Herold

Hmm I think the tree is long past the point where a little copper is going to hurt it much more. :^)

George H.

Reply to
George Herold

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

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...

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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Reply to
Jasen Betts

Google

dog water dish auto fill

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Reply to
FreeMan

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.

Reply to
George Herold

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!

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 

Viewed the eclipse at Wintercrest Farms, 
on the centerline of totality since 1998
Reply to
rickman

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 

Viewed the eclipse at Wintercrest Farms, 
on the centerline of totality since 1998
Reply to
rickman

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