I used to have a little biofeedback oscillator that I think was Radio Shack (but, that was 20+ years ago and the mind plays tricks).

Anyway, it was simple to use and effective. I'm trying to find a schematic (I'm sure it was simple as it was probably designed in the '70s). It had 2 rubber cups, similar to spark plug lead end cups, that slipped over 2 fingers and wired into the box. It had a single operational control which allowed adjustment of the oscillator frequency. To use, you'd adjust the oscillator to some frequency and then try to relax to reduce the pulse rate (sounded like a square wave). If the frequency got too low, you'd readjust the oscillator and continue. I'm sure it reacted to skin galvanic response or something similar.

I tried Googling it but, it seems like most results were for the $1k+ professional units and the associated text was high-falutin' medical lingo.

Seems like something that could be done with a 555 timer. Does anyone out there have some experience with this device or something similar? Or...a circuit design or ideas?

Thanks

 

I remember that thing, it was just a simple device that used your skin resistance to run an oscillator.

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com/

 

Have a look at this link:

http://www.samstoybox.com/toys/LieDetector/lie00.html

Does that look like the item you are talking about? I believe that Radio Shack first brought out the device as a "Lie Detector" and then later changed the name to something else to do with Bio Feedback. Page 6 of the linked manual shows the schematic.

I built one last year. It works exactly as you describe.

__________________
RadioRon

 

Interesting it uses a case from an intercom!

__________________
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That's the one, a 555 would be quite an advanced design compared to that.

What you may want is an E-Meter Same thing but this one detects aliens!

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com/

 

I had remembered it as being in a blue, rectangular box but, maybe I'd crossed brain neurons with my memories of, Captain Crunch. When I saw the photo on the cover of the instruction manual, it sure did look familiar (however, I can't discount the fact that I have owned RS intercoms so....).

Thanks for the quick and accurate responses.

Would have been nice if RS had shown the complete foil side of the pcb but, since I don't have that case, I guess it doesn't matter. Rather than try to reinvent the wheel with a 666 (Satan's version of the 555), I think I'll try to get off my lazy tush and do my own layout. If I have success, I'll post it to this thread, most likely as a .DXF file.

BTW: I have done some experimenting with using photocopy/laser toner as the resist for pcbs so, if anyone wants some do and don't do's from the trenches, feel free to ask.

I'll look into the "alien detector" but...with some trepidation. There are days I think I may be detected, myself.