Moisture meter?
Does anybody have a suggestion to make a moisture sensor? I would like
make a sensor that outputs a low voltage when soil is dry, and a higher
voltage (~4.5v) when the soil is wet.
I can make one with a high gain transistor and a led, but the transistor
won't work with the ADC and I am having a mental block.
Thanx
Matthew
make a sensor that outputs a low voltage when soil is dry, and a higher
voltage (~4.5v) when the soil is wet.
I can make one with a high gain transistor and a led, but the transistor
won't work with the ADC and I am having a mental block.
Thanx
Matthew
Comments
> Does anybody have a suggestion to make a moisture sensor? I would like
>make a sensor that outputs a low voltage when soil is dry, and a higher
>voltage (~4.5v) when the soil is wet.
>
> I can make one with a high gain transistor and a led, but the transistor
>won't work with the ADC and I am having a mental block.
>
>Thanx
>
>Matthew
>
>
>
>
>Hi Matthew, have a look at the sensing part of my setup I made some time ago.
You will have to change the chips to run it on 5v and also play with the
frequency
because on long run the capacitance of the twin wires wil afect it.
Good luck, Steve
Your moisture meter looks great! Could you post some aditional detail on the
list, like:
- what kind of probes did you use
- how works the sensor part
- how the full device works
- or any other about your soil moisture experience
Thank you!
Jorge Ferrero
Original Message
From: Svatopluk SKALICKA <steves@a...>
To: <basicstamps@egroups.com>
Sent: Friday, August 11, 2000 3:29 AM
Subject: Re: [noparse][[/noparse]basicstamps] Moisture meter?
>Hi Matthew, have a look at the sensing part of my setup I made some time
ago.
> You will have to change the chips to run it on 5v and also play with the
> frequency
> because on long run the capacitance of the twin wires wil afect it.
> Good luck, Steve
>
>
that I spent hours pulling my hair out instead of buying a $8 soil moisture
meter :-)
Original Message
From: "Matthew Lewis" <aiden.bell@h...>
To: <basicstamps@egroups.com>
Sent: Thursday, August 10, 2000 7:53 PM
Subject: [noparse][[/noparse]basicstamps] Moisture meter?
> Does anybody have a suggestion to make a moisture sensor? I would
like
> make a sensor that outputs a low voltage when soil is dry, and a higher
> voltage (~4.5v) when the soil is wet.
>
> I can make one with a high gain transistor and a led, but the
transistor
> won't work with the ADC and I am having a mental block.
>
> Thanx
>
> Matthew
>
>
>
>
which vary resistance with soil moisture. Probably
worth looking at in your local hardware store.
I hear that gypsum, commonly available in the form of
sheet rock [noparse][[/noparse]inside the cardboard!], makes a decent sensor
of moisture when you put it between two conductors.
With any resistive sensor bear in mind that if you use
DC current to sense the resistance you will often run
into polarization problems - as ions build up on one
side of the sensor the resistance changes even with
constant moisture. AC excitation across the sense
resistance prevents polarizing the electrodes.
Another possibility is to use a humidity sensor in a
"dry" air well dug into the soil.
Good luck
>>>
Date: Thu, 10 Aug 2000 19:53:59 -0700
From: "Matthew Lewis" <aiden.bell@h...>
Does anybody have a suggestion to make a moisture sensor? I would
like
make a sensor that outputs a low voltage when soil is dry, and a higher
voltage (~4.5v) when the soil is wet.
<<<
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>Hello Steve:
>
>Your moisture meter looks great! Could you post some aditional detail on the
>list, like:
>
>- what kind of probes did you use
>- how works the sensor part
>- how the full device works
>- or any other about your soil moisture experience
>
>Thank you!
>Jorge Ferrero
>
>
Original Message
Hi Jorge,
The moisture meter (sensor part), I have made some thre years ago, as is on
the schema to monitor solution
level in a tank and it is stil runing. It is mounted on the tank with wery
short, separated leeds going to the probes.
When the probes are gry, IC1b inputs are hold low by 10M resistor, when wet
(moist), oscilator formed by
IC1a, 100n and 33k charges through the probes and diodes cap 2n2 and taking
the inputs of IC1b high.
4093 NAND Schmitt Triger must have both imputs high for its output to go low.
I did made an oversight when drawing this schema. This I picked up during
the construction. As it is I would
have wrong polarity at the input to IC2a. On dry probes, its input must be
high. The second input is low
and waiting on high from the SEQUENCER to turn the relay on. I have put the
fourth gate, IC1d, of the IC package in series with the IC1c and connected
a 1k res. with green led in between them, when on, it indicates
moist condition.
The SEQUENCER consist of a timer, using 4060 Ripple Counter. It has build
in oscilator. The timing is selected
(changed) on the 10 way DIL Switch. 4017 is a counter with 1-of-10 outputs.
With reset connected to the ground
you get high on the Q0 to Q9 one by one, only one at a time, nonstop. The
duration of the high is preset on the firt 10 way DIL Switch. On the second
10 way DIL Switch you select the lines you want to have on (or off).
The high signal from the Sequencer goes to the second input of IC2a and if
its first input is also high,
on dry probes, the output goes low turning on the PN200 and the relay.
When I finnished this, on the benchtop it worked perfectly for two days bud
I did run into trouble when
connecting it to the twinwires, 30 to 50m long, going to the probes. Its
capacitance must have caused a curent
leaking across and indicating high without the probes being yet connected.
I lowered frequency of the oscilator by replacing 33k res. with 470k. That
did fix it. You could encounter the same problem if you run
the wires close to the power mains, picking up strays. In this case the
only solution would be to make
the sensor a part of the probe with common, +12v and signal wires going to
the rest of the unit or using
shielded cable.
For the probes, well, unles it is for a laboratory or similar use, what
ever you can make.
It may be a block of rubber or plastic, (nonconductive), with two pieces of
solid core bare coper wire embeded
in it and slightly protruding to be used in a mist propagating greenhouse
to anything similar to what I made.
200mm lenghts of the aloy car brake line, with pieces of insulated wire
soldered to it at one end, on the outside, before pushing through it the
thickest insulated solid core copper wire that would fit in and fixing
it at both ends with epoxy. Two wires at one end are connected to the
moisture sensor. At he other end I trimed the wire to about 4mm and striped
the insulation. Nothing fancy.
The only reason I did his unit is to prevent drop of water presure when to
many lines are open at one time.
Witht this only one line is open at any one time and only if that area does
need to be watered.
It should be feasible to replace the sequencer and gates with a stamp.
Sorry for my english, I wasn`t born speaking it and didn`t learn it at school.
Saludos, Steve
Thank you very much for your explanations; I understand your device enough
as for beginning my own experience. Your experience, advices and comments
will be very usefull for me!
...and your english is very good! (English is not my native language
neither)
best regards
Jorge
Original Message
From: Svatopluk SKALICKA <steves@a...>
To: <basicstamps@egroups.com>
Sent: Wednesday, August 16, 2000 4:43 AM
Subject: RE: [noparse][[/noparse]basicstamps] Moisture meter?
> >
Original Message
> Hi Jorge,
> The moisture meter (sensor part), I have made some thre years ago, as is
on
> the schema to monitor solution
> level in a tank and it is stil runing. It is mounted on the tank with wery
> short, separated leeds going to the probes.
> When the probes are gry, IC1b inputs are hold low by 10M resistor, when
wet
> (moist), oscilator formed by
> IC1a, 100n and 33k charges through the probes and diodes cap 2n2 and
taking
> the inputs of IC1b high.
> 4093 NAND Schmitt Triger must have both imputs high for its output to go
low.
> I did made an oversight when drawing this schema. This I picked up during
> the construction. As it is I would
> have wrong polarity at the input to IC2a. On dry probes, its input must
be
> high. The second input is low
> and waiting on high from the SEQUENCER to turn the relay on. I have put
the
> fourth gate, IC1d, of the IC package in series with the IC1c and connected
> a 1k res. with green led in between them, when on, it indicates
> moist condition.
> The SEQUENCER consist of a timer, using 4060 Ripple Counter. It has build
> in oscilator. The timing is selected
> (changed) on the 10 way DIL Switch. 4017 is a counter with 1-of-10
outputs.
> With reset connected to the ground
> you get high on the Q0 to Q9 one by one, only one at a time, nonstop. The
> duration of the high is preset on the firt 10 way DIL Switch. On the
second
> 10 way DIL Switch you select the lines you want to have on (or off).
> The high signal from the Sequencer goes to the second input of IC2a and if
> its first input is also high,
> on dry probes, the output goes low turning on the PN200 and the relay.
>
> When I finnished this, on the benchtop it worked perfectly for two days
bud
> I did run into trouble when
> connecting it to the twinwires, 30 to 50m long, going to the probes. Its
> capacitance must have caused a curent
> leaking across and indicating high without the probes being yet connected.
> I lowered frequency of the oscilator by replacing 33k res. with 470k. That
> did fix it. You could encounter the same problem if you run
> the wires close to the power mains, picking up strays. In this case the
> only solution would be to make
> the sensor a part of the probe with common, +12v and signal wires going to
> the rest of the unit or using
> shielded cable.
> For the probes, well, unles it is for a laboratory or similar use, what
> ever you can make.
> It may be a block of rubber or plastic, (nonconductive), with two pieces
of
> solid core bare coper wire embeded
> in it and slightly protruding to be used in a mist propagating greenhouse
> to anything similar to what I made.
> 200mm lenghts of the aloy car brake line, with pieces of insulated wire
> soldered to it at one end, on the outside, before pushing through it the
> thickest insulated solid core copper wire that would fit in and fixing
> it at both ends with epoxy. Two wires at one end are connected to the
> moisture sensor. At he other end I trimed the wire to about 4mm and
striped
> the insulation. Nothing fancy.
>
> The only reason I did his unit is to prevent drop of water presure when
to
> many lines are open at one time.
> Witht this only one line is open at any one time and only if that area
does
> need to be watered.
> It should be feasible to replace the sequencer and gates with a stamp.
>
> Sorry for my english, I wasn`t born speaking it and didn`t learn it at
school.
>
>
> Saludos, Steve
>
>
----
>
> Svata (Steve)
> http://skalicka.8k.com
>