Help electricians !!!

dw

This may sound a little weird but just bear with me here·.........
I am doing a college project. I am using minute electromagnetic activity in plants (thats right as in organic plant)·or other organism·to trigger off midi in a computer via an atom chip attached to a circuit board. Basically it goes like this:
·plant > atom chip > midi > computer
Obviously I need a positive and negative attached to the plant or no potential difference· will be created (the positive is the input of the preamps)
My question is this·:

Do I earth the plant just to the negative inputs of the preamps , or do I connect all the negatives (including preamps,plant, batteries)·to the·0 volts ( vss ?)·on the circuit board ?
If anyone wnows what im talking about help would be very much apreciated !
Gus

allanlane5

The voltage potential you will be measuring should be that of the plant, as against the ground.

I would put a copper rod into the soil, and use that as my ground. Moist, fertile soil has pretty good conductivity.
Then, I would tie the grounds -- Vss, Pre-amp, plant, and batteries -- to a single point so they all share a common reference.

You can probably amplify the signal from the plant with an op-amp or two.

Forrest

FYI the Basic Atom chip is not made by Parallax - it's made by Basic Micro. You'll probably get more help on the Basic Atom if you go here forums.basicmicro.net/

dw

Brilliant thanks. Just one more query - when you say tie the earths to a single point, would that for example be the rod in the ground ? What would be the result if all the earths were just earthed to the·vss ? I may not have acccess to the ground (soil)·unfortunately as twill be indoors.

allanlane5

Hmm. You have access to the plant, but you don't have access to the dirt the plant is planted in?

The rod I was speaking of (and it could just be a length of 8-guage solid copper wire) was to be put into the soil the plant was planted in.

And 'earthing' to Vss would be fine.