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Author Topic: Extending biofeedback electrodes?  (Read 213 times)

Offline alinta

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Extending biofeedback electrodes?
« on: March 23, 2018, 12:29:37 AM »
Hi Sam and all,

I am experimenting with my MidiSprout and I was hoping to set up an installation where one of the biofeedback electrodes (probably without pad) can fit down the neck of a thin jar and go into some soil inside the jar. The other electrode would stay outside of the jar for a human to touch (again, probably without pad since there would be multiple people touching it over time). Soil can't make noise from the Midisprout by itself, but it can if a human is touching just one of the electrodes.

I'm trying to figure out the best way of putting the electrode into the soil. I guess I could just mash it in there and see what happens, but it might not fit into the jar. I have seen these long thin needle electrodes for going under skin: https://bio-medical.com/rhythmlink-disposable-paired-13-mm-subdermal-needle-electrode-10-pairs-per-box-13mm-6-color-group-1.html and am wondering whether anyone has tried to extend the usual Midisprout electrode with some attached copper wire, for instance? By this I mean a wire that is glued/wrapped to the metal part of the original electrode itself, not actually cutting or modifying the electrode wires in any way! Do you think this is possible or would it cause a shock to the human on the other pad? I don't want to set up something that might cause a jolt.

Cheers, Alinta

Offline alinta

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Re: Extending biofeedback electrodes?
« Reply #1 on: March 23, 2018, 08:58:36 PM »
Hi again,

I'm having a little trouble with the above experiment as it works fine on wet soil outside, but once the soil dries up and is put in a jar, there's no moisture or current to be picked up (you're probably thinking 'well duh' but I'm going to force this to work somehow!). I'm thinking I need to put something else in the jar to help it along - what else can I put in there that won't go dry, but will create a current? I could grow a plant or maybe fungi (?) in there, but I am hoping for something small and perhaps human-made.

Or perhaps it needs 'grounding' somehow? Is it because the jar is glass?

Any suggestions greatly appreciated.
« Last Edit: March 23, 2018, 09:36:23 PM by alinta »

Offline sam

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Re: Extending biofeedback electrodes?
« Reply #2 on: March 26, 2018, 01:55:14 PM »
Yes, dry soil doesn't conduct electricity very well (unless wet). 

The biodata sensor uses two electrodes which measure electrical conductivity between the trodes.

Essentially, your experiment shouldn't work if the user is holding a glass jar, that glass will insulate and prevent the user from being measured.   

Now ... there are many situations where strange electrode configurations will produce 'output' (like put one trode on one person, the other trode on another person, and then move really close together without touching).

Sometimes moisture/humidity in the air is enough to allow a small flow of current... but the best way to use the tool is to have a good solid connection with the organic system which is being studied.