we'll see about the stand alone unit once we get there the ideal case i think would be to have a microcontroller operate the device, with enough flash memory to record some significant data... then you could use it in the mountains, but if you'd still like to see a graph of your night's sleep, you could plug it into the computer, do the transfer of data and see it on screen... kinda like the super nova dreamer i suppose... or maybe the real time computer connectivity would be switchable, on and off... if you just want rem detection you wouldn't get all the fancy data, but i you happen to have your computer around, you can push a button and make the connection happen... but we're still pretty far away from there... and the GSR is the reason why hehe.

GSR (galvanic skin response) is an old (and aparently out of date since the 70's or so?) term wich refers to the electrical activity on your skin (the skin itself acting as a series of resistors)... To clear up some of the confusion, the proper terminology is now electrodermal response, which can split into several types of response... you can have SCL (skin conductivity level) or SCR (skin conductivity response, which is the change in conductivity level)... or SRL (skin resistance level) and SRR (skin resistance response)... and so on... GSR used to refer to the SRL and SRR, since it measures the resistance of skin.

What we're building is something that measures the resistance level, since it's of higher value... at the same time, the resistance level is a function of the conductivity of the skin, so by knowing the resistance and knowing how much electricity you run across the surface of the skin (0.5V) you can figure out the conductivity as well... So with one pretty sensitive unit, you can figure out both... The reason is because, apparently, during REM sleep, electrodermal activity is different than at any other time of day. For now, we're just trying to figure out HOW it's different and how this change can be used to detect REM...

"EDA consistently
decreases during the six minutes preceding a REM period and can be used to detect
REM-phase onset (Koumans, Tursky, & Solomon, 1968). An early study by Broughton,
Poire, and Tassinari (1965) found that when EDA does occur in REM sleep, it is often
accompanied by bursts of eye movement activity (REM)."

From what I read, there is also a lot more electrodermal activity in deep sleep, which then drops significantly when you enter REM... We're hoping this drop will be enough for us to detect REM.

The problem of course is that they don't say WHAT exactly changes... which goes back to measuring distance between peaks or amplitude of response... but this we'll figure out when the time comes... For now we just need a somewhat reliable "GSR" unit...

Which brings me back to the new design. We'll have to use a trimmer pot (it will appear as a tuning knob outside the box for now) in oder to center the signal for each individual... I'm combining the design from the wireless GSR that I posted earlier (with the operational amplifier) with the design that splits voltage across a resistor and your skin. The trimmer pot will be used to change the resistance of the resistor that's in series with your skin, so that if your skin for instance has a natural level of around 200Kohm it won't show on the graph very high up as opposed to someone who's resistance level is... sat 30kohm, which would show up very low on the graph.

This is simply to calibrate the software easily. If the fluctuations in skin resistance are about 25kohm, then the range of the graph should have to be say... 50 kohm at max, instead of 250 kohm... and to determine the 0 or the middle value you'd have to do a quick calibration till a LED light goes on (which is simple, you just turn until you turn a led on and that's basically it, you start monitoring).

If we skip this, then the graph would have to have a variable range, and i don't know how practical that is with the programming (a variable range in a graph would be awesome nonetheless, because you'd be able to zoom in and pick up small fluctuations as well as big ones).

But for now we'll have to have the trimmer pot (it's possible to just take it out and replace it with a set resistor, but it wouldn't be as precise and it would complicate the programming i think)

I'm hoping this weekend I'll be able to start working on the hardware. We'll switch to a 9V battery (we have to get a 3V or a 5V for the voltage to frequency part, and i thought instead of 3 AAA for 3V we might as well go for one 9V and reduce it to 5V)... I have most of the parts (except for a few for the oscillator clock, which I hope I can get soon)...

And yeah, if Placebo can get a small program to show up sound frequency on screen, that would be great.

And Cerebusdreamer, do you know stuff about either programming or electronics ? given a schematic, would you be able to build your own device or have someone help you build it ? As soon as I get the first two done (one for me and one for placebo so he can do the software) and I know they work (in that I can see a fluctuation in frequency on screen) I'll draw up schematics and plans of construction for both the device and the sensors. (that's another thing, it would be nice if the sensors would have jacks so you can plug them in, rather than have them stuck to the unit... this way you'd be able to change the sensors when they wear out without having to open it and unsodder or cut wires, etc)... Hmmmm hehe yet another idea. I'll try to find simple jacks as well then. Headphone jacks or something would work (this of course would be optional)

... what is it with me and long posts? I guess I'm just overly excited about most things most of the time...