I put together a ‘lie detector’ testing for galvanic skin response.

I didn’t work.  I tested various obvious different ideas, such as looking at variances from a sliding window mean etc, but didn’t get anywhere.

It does light up if I hyperventilate though, which is er, useful?  It is also, interestingly, lights up when my daughter uses it and shouts out swear words, which she finds highly amusing.  I think it’s just detecting her jerking her hand around though.  She doesn’t exactly sit still.

I used an op-amp to magnify the signal 200 times analogue-y (er, as opposed to digitally..), but I now wonder if I could use a high resolution (e.g. 40bit) digital to analog converter directly, and do more processing in software.

Perhaps even use a neural network to train to train it to detect lies.

I did order a 40bit AD evaluation board from TI, but haven’t had the chance to actually use it yet.