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Singing plants, advice please.

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steve_j83

New Member
Well not really singing plants as such, but i'll explain that in a second.

Firstly im new here so big hello :D and to give you a little info about me... I confess I know very little about electronics, i learnt a little as a kid and curently trying to catch up reading as much as i can at the moment but could use a little help (ok well maybe alot).

Im curently working on a university project, i study sound arts and design and i am looking to create a sound instalation/performance piece based on responses from plants.

This is inspired by some work done in the 60's and 70's that shows when a plant is stimulated the resistance varies and i will be using this to trigger and alter parameters of a sound. I will be using an arduino board to input voltage changes into max/msp where i will convert that data into sounds. I have that all sorted but i need help with the electronics.

Now here is where i am struggling. I need to make a device that will measure resitance variations in the plant tissue. When a plant is stimulated (in this case physically) the resistance varies (much like in a person).

Now i will not be marked on the electronics as my marks are on the concept and how is sounds so i am free to get assitance with the electronics, how ever any help i do recieve i am more than happy to credit the individuals should anyone wish.

I was looking at making a weatstone brige and an amp, but i eventually stumbled upon this article which seems to be alot of the work done for me!
The article will give you a better overview of what im talking about.

If you could have a look at the second link. It is the schematic for the system.

http://www.swtpc.com/mholley/PopularElectronics/Jun1971/PE_Jun_1971_pg63.jpg
http://www.swtpc.com/mholley/PopularElectronics/Jun1971/PE_Jun_1971_pg64.jpg
http://www.swtpc.com/mholley/PopularElectronics/Jun1971/PE_Jun_1971_pg65.jpg
http://www.swtpc.com/mholley/PopularElectronics/Jun1971/PE_Jun_1971_pg66.jpg
http://www.swtpc.com/mholley/PopularElectronics/Jun1971/PE_Jun_1971_pg67.jpg
http://www.swtpc.com/mholley/PopularElectronics/Jun1971/PE_Jun_1971_pg68.jpg
http://www.swtpc.com/mholley/PopularElectronics/Jun1971/PE_Jun_1971_pg93.jpg


Looking at the schematic here where i am struggling

1. The input output polarizer. How does this work? I dont really understand how it would be wired. Its confusing me quite a bit, why have the tracks comming from the electrodes (bp 1 and bp2) been crosed over each other?

2. How viable is this in terms of part avalibility? I think the ic might be a little out of date but shouldnt be to hard to find a sutible replacement. Any advice as a whole?

3. I need the output to be in a voltage range of bewteen 0-5volts. A range of 0-1 would suffice though. Where would be the best place on the schematic for me to take the output to be sent into the arduino? At the dc recoreder or the audio output? Im asuming the dc recorder but im not sure what voltage range it will be outputing.

Im sure there will be plenty more questions to come but thanks for reading this far. If you need any clarification on anything just ask and any help, advice or ideas would be much apreciated :)

Steve
 
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JimB

Super Moderator
Most Helpful Member
First of all, well done in explaining exactly what it is you are trying to do, clearly explaining the problem and obviously making a start on the work yourself.
UNLIKE many of the idle third world students (and some first world) who come here expecting the complete work done for them. Oh and they need it by next week!
[rant_mode: OFF

Looking at the schematic here where i am struggling

1. The input output polarizer. How does this work? I dont really understand how it would be wired. Its confusing me quite a bit, why have the tracks comming from the electrodes (bp 1 and bp2) been crosed over each other?
Quite simple, it is just a double pole double throw switch with a simple wiring scheme (very simple when you see it done) to swap the polarity of the input signal from the plant to make the meter move in the correct direction.

2. How viable is this in terms of part avalibility? I think the ic might be a little out of date but shouldnt be to hard to find a sutible replacement. Any advice as a whole?
The IC in the circuit, the 741 is still readily available, however, before the pack descends and tells you it is old and inferior, I will just say that something like a TL071 would be a better choice.

3. I need the output to be in a voltage range of bewteen 0-5volts. A range of 0-1 would suffice though. Where would be the best place on the schematic for me to take the output to be sent into the arduino? At the dc recoreder or the audio output? Im asuming the dc recorder but im not sure what voltage range it will be outputing.
First of all, what is an arduino? (On edit, OK I just googled it!)
The output voltage will depend on the input from the plant, so, dificult to predict.
I think that you need a DC voltage, so the recorder output is probably what you need to use.

JimB
 
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steve_j83

New Member
Hey Jim, thanks for the good info, i still have a few months to finish this but hoping to get a prototype working in the next month.

Quite simple, it is just a double pole double throw switch with a simple wiring scheme (very simple when you see it done) to swap the polarity of the input signal from the plant to make the meter move in the correct direction.JimB
Ok well you lost me there but i will have a look around at the terminology and some examples and see if i can get my head around it :) If you say its simple i should be fine.

I will just say that something like a TL071 would be a better choice.
Great will look into it, need to get my head around IC's will check back on that when i understand a little more.

The output voltage will depend on the input from the plant, so, dificult to predict. I think that you need a DC voltage, so the recorder output is probably what you need to use.
Ok cheers guess im best to just build the thing and see how we go.

Two more questions though,

can i remove the audio amp if im not going to use it? If so which components are free to go.

And the arudino offer's single pin analouge inputs and a ground pin, so from the dc out do i run the positive current into an analouge input pin and the negative into the ground pin? im a bit lost here.

Thanks again
 

JimB

Super Moderator
Most Helpful Member
Try this as a modified circuit.

On further thought, you could probably leave out the meter.
Also the 0.01uF capacitor.

JimB
 

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steve_j83

New Member
Thanks jim, thats really good of you, am really chuffed. You have saved me alot of hair pulling, i'll try get this up and running over the next couple of weeks (end of term atm so i am a little snowed under now) and i will let you know how i go. Also do u have a last name Jim, as i would like to credit you for the modifed design ?
 

Mikebits

Well-Known Member
I am really a bit sceptical to this whole idea. Plant physiology really does not seem to lead one to believe that plants could respond to sound. They just don't have a mechanism for doing so. Most of a plant biological makeup is chemical reaction. The plant stoma open and they draw in CO2, at same time the stoma draw water from the root through the xylem tissue. All Chemistry based. Plants have no CNS, so I think the whole idea of plants reacting to sound is somewhat silly.

Measuring resistance change would be nothing more than coincidental. Ie. plant is uptaking water with nutrient in it. Certain nutrients would affect the electrolyte levels of the plant thus creating an illusiion that the plant was undergoing some sort of change. Just silly I think.
 
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steve_j83

New Member
Hey Mike. I think you might have misread things a little. It’s not that the plants will be responding to sound, although there is a lot of scientific research suggesting that cretin music does stimulate plant growth. That is a whole different issue that is debatable and something I don’t understand myself.

However it is well documented that plants the resistance in the plant tissue does alter when a plant is physically stimulated. The truth is we understand very little about plants, for example the venues fly trap. It has no central nervous system (as you mentioned) but are more than capable of registering when it is touched and physically responding.

What I will be doing is recording resistance changes that occur when a plant is touched. Each plant will be set a base line and then once physically stimulated the variations in the data collected will control (in real time) some specifically designed electronic instruments.

Essentially I will be using the plants as a sort of controller to create abstract music. I understand your skepticism though. I guess we will just have to wait and see. I will be more than happy to post the results either way.
 

steve_j83

New Member
I had a look at the switch, i think i understand it. Is this correct?

(hardly pro but I only had paint on hand)
 

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JimB

Super Moderator
Most Helpful Member
Your second drawing is correct as per the circuit.
However, either connection scheme will work correctly.

In answer to an earlier question, my real name is Jim Butler.

JimB
 

Boncuk

New Member
Hi Steve,

might decide to try another approach using an instrumentation amplifier.

Here is one suggestion: AD8223 (Analog Devices).

It's amplification factor is variable from 5 to 1,000. The input voltage might be as low as 150mV below the negative rail.

It also features a full output swing from positive to negative rail.

I do know that plants react to stress. If you pinch it its tissue resistance changes in pain. Plants should be able to cry, which is desireable here in Thailand. People just chop what they want for food (or what is their way) because the flora is very generous here.

Boncuk
 
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steve_j83

New Member
Ok i have set this up on a bread board but i think i have gone wrong somewhere.. For some reason i am getting a negative read out... I have checked and check again, also pulled everything apart and started again, still the same result..

I currently have a 220k resitor across bp1 and 2 (roughly the level of resistance i am expecting) and i get a readout of between -0 and -0.0865v depending on the position of R2

Any one have any suggestions?
 

JimB

Super Moderator
Most Helpful Member
OK, firstly what values of resistors are you using for R1 R2 and R3 ?

If you make the R1 = 220k the same as BP1 to BP2, use a test meter to measure the voltage between the slider of R2 and the junction of R1 and BP1/BP2, as you adjust R2 you should see the voltage vary from some -ve value through zero to a +ve value.
You may want to try this with the amplifier part disconnected from the R1 R2 R3 circuit.

JimB
 

steve_j83

New Member
Thanks Jim have got it sorted now.

I have just given it a run on a plant.. but the resitance on the leaf was too high so i have taped into the base of the plant, better now, only thing is its a stable reading, and throwing switch 3 makes no difference to the reading and the position of R3 has no effect.
Is this right?
 

steve_j83

New Member
Ok now im really confused... Im haveing a starnge problem with my TL071, well both of them...

I have to Op amps... but they behave differently.. The first one overloads the meter and i get a voltage reading of .08 v but when i swap the other one over i get a negative voltage of -.08 v

Whats going on??
 

JimB

Super Moderator
Most Helpful Member
The two op-amps should behave identically assuming that they are both OK.

If they are behaving very differently then either:
1 one or both chips is faulty.
2 the external circuitry is not wired correctly.

JimB
 
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