An Unexpected Problem with my Brainwaves Appliance Controller

RE: An Unexpected Problem with my Brainwaves Appliance Controller

johnbeetem — Wed, 26 Mar 2014 19:56:47 GMT

I'm not an analog expert, but from your 'scope trace it looks like the high-amplitude noise bursts are about 8.3 msec apart, which inverts to 120 Hz. My non-expert SWAG is that you're picking up 60 Hz noise through all that wiring. Are you in a country with 60 Hz electricity? You might try switching off lights (especially if fluorescent) and see if that affects what you see.

Just a guess.

RE: An Unexpected Problem with my Brainwaves Appliance Controller

DAB — Wed, 26 Mar 2014 19:29:44 GMT

Hi Cosmin,

It looks like you might have some cold solder joints on your board.

The connection from the plug through the 330 ohm resister to the orange wire looks very suspicious.

You might want to go through the circuit and verify good connectivity.

Then you might want to do some component checks on your internal circuit components.

DAB

RE: An Unexpected Problem with my Brainwaves Appliance Controller

vsluiter — Wed, 26 Mar 2014 08:03:11 GMT

Hi Cosmin,

Have you verified that your amplifier IS working correctly? You might want to trigger your scope on the input signal, and view the output signal on your scope, but average over a few 100 samples. The noise should then be partly cacelled, and the signal should remain. You also might want to look at the intermediate stages of your instrumentation amplifier (ouput of opamp 1 & opamp2).