Simple MYO sensor...

After struggling with Neurosky Mindwave headset a lot I decided to make my own sensor to use in some bio sensor projects... I found that there is a cheap and easy to use instrumentation amplifier signal interpreter IC, AD620AN... 

You can see the connection details on the above photo... Only one external resistor is needed as reference and I used a 1K pot for the purpose, this enabled me to adjust sensitivity... Only drawback is the need to use a symmetrical power supply, which is not an issue if you have a ATX power supply... Otherwise you have to use two batteries serial connected and use middle as gnd... This simple MYO sensor can create distinguished signals if electrodes are well placed... Signal is logic level and can be fed directly to Arduino input port which can then be interperted by software...


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GroG's picture

Thanks borsaci for the post !

Thanks borsaci for the post !  ..  I have not been impressed by the Mindwave either, I think its primarily a product of greed and not the greatest sensor.  Thanks for a creative alternative.  Its a bit hard to make our your circuit drawing.. 

I found another reference on the net.. looks similar

Specs

I would be curious to know what exactly is happening.  Why are negative and positive voltages needed.  Does my body have an operating ground?  Does myo activity generate negative & positive voltages in relation to that ground ?  Of the 3 contacts what is the "sensor"?

borsaci06's picture

myo sensor...

Well I do not kno─▒w the exact details of the IC but it is a comparator, op-amp, signal interpretor... 2  electrodes is used to detect a single signal... A single resistor is neded between pins 1&8 (as reference) which is mostly used as 200ohms but I used a 1K pot for the purpose which proved to be more usaful (for adjusting sensitivity)... what is more, I also grounded the third leg of the pot so now I do not need the body ground which is shown as a 3rd electrode to the feet... With only 2 electrodes to a single muscle (or both sides of forehead) I can detect either my arm muscle movement or facial expression (if connected to forehead)...that is... I only use the 2 contacts for a single sensor... the symmetrical voltage is needed for the internal working of the comparator... for sensing different muscles, you need different AD620s.. but the IC is small enough to place over the muscle band which has 2 electrodes...