REM Detectors (again)

**Durett** · 01-29-2008 04:44 AM

Alright, here’s my semi-analysis of the circuit contained at the bottom of the pdf at the website http://affect.media.mit.edu/pdfs/05.strauss.pdf for the gsr circuit. I would change the circuit so that in the first amplification stage, you have 2 1M resistors, a 500k resistor, and a 250k resistor in parallel. I probably made many mistakes, major or minor, so just correct me. An analysis is important before you build a circuit because, well, if you want to change a few factors, you have to know what you’re doing. Look at the schematic,
or else you’ll have no clue what I’m talking about. So here it is…

First, an overview of the circuit. There are two amplification stages. The first one has 4 gain stages. The first has a range of 0-5 uS, the second 4-10 uS, the third 8-20 uS, the fourth 16-40 uS. S stands for a Siemen, while the u stands for micro (10^-6). A siemen is equal to 1/resistance. Therefore, 5 uS = 1/(5*10^-6) ohms = 200,000 ohms. The corresponding ohmic ranges, from first to fourth gain stage, are 200,000 + ohms; 250,000 to 100,000; 125,000 to 50,000; and 62,500 to 25,000 ohms. The second amplification stage shifts the range of voltage into the 0-2.5 V range required by the PIC microcontroller for its Analog to Digital conversion.
Let’s take a look at the first amplification stage. The input voltage to the + side of the op amp is .5 V. The capacitor on the – side is simply meant for noise filtering. The voltage gain of this noninverting amplifier configuration can be shown to be 1+R/Skin where R is the equivalent resistance of resistors R3, R4, R5, and R6 (depending on which ones are connected).
The mode depends on whether the appropriate electronic switches are open or closed. The microcontroller controls the state of the switches . The switches are actually contained in the ADG712BRU integrated chip.
In the second gain mode, the 2 1M resistors are connected in parallel. Therefore, R = (1*10^6)^2/(2*1*10^6) = 500,000 ohms.
Therefore, the gain in mode 1 is 1+500,000/(100,000) to 1+(500,000/250,000) = 6 to 3. The output voltage range is therefore .5 * 6 = 3V to .5 * 3 = 1.5 V. The same calculations can be made for modes 1, 3, and 4.

Mode 1: R = 1,000,000 ohms. Gain is 1+(1,000,000)/(200,000) = 6 all the way down to 1 (as skin resistance approaches infinity, R/Skin approaches 0). Therefore, voltage range is from 3V to .5 V.

Mode 3: R =250,000 ohms. Gain is 1+(250,000)/(50,000) = 6 to 1+(250,000)/(125,000) = 3. Voltage range is from .5*6 = 3V to .5*3 = 1.5V

Mode 4: R = 125,000 ohms. Gain can be calculated to be from 6 to 3, which in turn produces an output voltage of 3 to 1.5V.

All right, to sum it up we have 4 modes that produce an output voltage from 1.5 to 3 V for stages 2,3, and 4 while producing output voltage of .5 to 3V.

On to the second amplification mode! The voltage input into the second op amp can be seen to be 11/21V (V is output of first amplification stage) with only the 100k resistor in series with the 110k resistor going to ground.

The voltage output of the second amp can be derived as V-20*10^3*((V1-V)/(26.4*10^3)+(V2-V)/(132*10^3)) where V = the input voltage into the + side of the op amp, V1 and V2 can be 3.3V or 0V, as controlled by the high and low state of the microcontroller (it is powered by a 3.3V regulator). Of course, the low voltage won’t really be 0 V and the high voltage won’t really be 3.3V. This probably means that, to get the best accuracy, you would have to record the voltage level of your individual microcontroller at home and change the computer software as appropriate.
Anyways, since I’m getting tired already, and you’re getting tired of reading this stuff, suffice it to say that in order to subtract .5V from the first amplification stage you need a 100k resistor alone, while in order to subtract 1.5 and multiply by 5/3, you need the 100k resistor in parallel with the other two resistors that are also in parallel (24k and 91k. Atleast that’s what I think 24k||91k means in the schematic in the pdf file). The second part just mentioned is actually just an approximation, but the error is so small, that a 10 bit ADC won’t detect the difference.

Now it’s time to calculate the accuracy of each mode!

The minimum change in voltage the ADC can detect is 2.5/(2^10) = 2.5/1024 = .0024414 V. The output voltage for modes 2, 3, and 4 is (.5* (1+R/skin)-1.5)*5/3 = V, where V = output voltage. First, solve equation for skin resistance given output voltage. Skin = 5*R/(6*V+10) .

Starting with mode 2, V max is 2.5 V, while minimum is 0 V. Letting R= 500,000 ohms, the error can be calculated at 2.5V (100,000 ohms skin resistance) to be
5*(500,000)/(6*(2.5-2.5/1024)+10) -5*500,000/(6*2.5+10) = 58.6 ohms.
At 0V (250,000 ohms skin resistance) error is Abs(5*500,000/(6*(0+2.5/1024)+10)-5*500,000/(6*0+10)) = 365.7 ohms. These errors correspond to percent errors of (365.7/250,000)*100 = .14628% to (58.6/100,000)*100 = .0586%.

Next, mode 3. R = 250,000 ohms. V max is 2.5 V, while minimum is 0 V. Error is from 29.3 ohms (at 2.5 V) to 182.8 ohms (at 0 V). This corresponds to a percent error of (182.8/125,000)*100= .14624% to (29.3/50,000)*100 = .0586%.

Next, mode 4. R= 125,000 ohms. V max is 2.5 V, min is 0 V. Error is 14.6 ohms (at 2.5 V) and 91.4 ohms (at 0 V). This corresponds to a percent error of (91.4/62,500)*100 = .14624% to (14.6/25,000)*100 = .0584%.

Finally, the awesome mode 1. We need to derive a different formula for this, since in the second mode of amplification only .5 V is subtracted rather than subtracting 1.5 V and multiplying by 5/3.
The formula is .5(1+R/skin)-.5=V, where V= voltage output. Solving for skin, we get
skin=R/(2V)

At 2.5V (200,000 ohm skin resistance), error is 1,000,000/(2*(2.5-2.5/1024))-(1,000,000/(2*2.5)) = 195.5 ohms.
This corresponds to an error of (195.5/200,000)*100 = .09775%. Notice that we subtracted (2.5-2.5/1024) because this will give us a larger error than adding (2.5+2.5/1024). As V gets smaller, the error increases rapidly (the skin resistance measured gets larger).

Let’s calculate the skin resistance that will produce an error of 1.0%. Set up the equation …
((1,000,000/(2*(x-2.5/1024)))-(1,000,000/(2x))) /(1,000,000/(2x))* 100 = 1
Solving, x = .246582 volts. This corresponds to a skin resistance of 2.028*10^6 ohms. Unfortunately, 1% of this is a 20,280 ohm error! At x = .5 V, skin resistance would be 1*10^6 ohms. This level will correspond to an error of 4906.77 ohms. If we switch to a 12 bit ADC converter (you can get microcontrollers that have this level of ADC built in), the error that corresponds with a skin resistance of 2.028*10^6 would be 5031.57 ohms.

Alright. Now it’s time for a preliminary part cost list of the integrated chips used (didn’t include resistors, capactitor, diodes, because I didn’t feel like it. So cost is higher. Also, it doesn’t include Bluetooth since we can just connect it serially to the computer)

ADG712BRU: $2.00
OPA2342EA: $2.36 *2 = $4.72
PIC16LF88 = $5.33
3.3 Voltage Regulator: $1.13
Total: $13.18 + $8.00 (shipping, maybe more) = $21.18

We could probably find a cheaper microcontroller than the PIC (somewhere around $2.00, say an atmel tiny) but I’m just going with what they used. Alright… Next, I shall look at the other possibility mentioned, using a frequency to voltage converter. Even if this way is not cheap enough, still some ideals concerning using the skin resistance to change the op amp amplification is good to know.

It’d be good to discuss and generate more ideals, suggest improvements on this circuit to make it cheaper/more accurate, etc… Till then, au revoir!

**Durett** · 01-29-2008 04:46 AM

Woops... Didn't format when I copied from microsoft word...

**Durett** · 01-30-2008 04:02 AM

Just off the top of my head, it would be nice to study the techniques used in electrometers to get such accuracy.
Oh, and I was taking a look at a previous ideal to use a voltage to frequency converter to measure the voltage, and by this, the resistance. I was just wandering, does anyone have any ideal on how to accurately measure high frequencies using a pc without sucking down the resources?

**Placebo** · 01-30-2008 08:58 AM

Nope sorry. Like I said before, I'd love to help, but my electronics knowledge is dangerous at best.
It was a long technical post, so let's see if someone else (maybe Seeker) gets time to figure it out

**davidcaudron** · 01-31-2008 07:58 PM

Hello every body,

I am new comer in this forum (and in lucid dream resarch), and i would like to know if it is the right place for debates about piezo sensors for eye movement detection. The start of the thread was a little general but it seems that you ve been focusing on GSR since a while, so if you want me to deplace my response, just tell me.

I ve been actually awared by a specialist that IR could actually warm the liquid contained inside the eye ball without any alarm from our senses because illumination occurs behind the "right place" (i don't know the english word for it"). Then, for a home made device, i think this technologie is a little bit unsafe.
So, i 've been looking for another way, and i found out that the NASA, has actually used piezo sensors, for eye movement detection, monitoring that way paradoxal sleep.
Here is the kind of sensor i am talking about:

http://www.meas-spec.com/advizia/v41...=Piezo&Rnd=124

What do you think of it? any specialist around for a new dream mask generation (USB 2.0 required

)

**Durett** · 02-04-2008 11:00 PM

That sounds like a good ideal! Do you have any more information on it, like how the circuit was made? And, it appears that you have to call to order it... is this the only place you can get it or are there others?
Cheers!

**Durett** · 02-12-2008 01:33 AM

I haven't posted lately, but right now I'm trying to get a very uncooperative microcontroller (atmega16) to program. One moment it programs (I'm using winavr software) and the next time it says the stupid microcontroller isn't responding... Anyways, I've decided before I order anything that I should try out a basic rc circuit to see if this will work for general gsr detection. The resistance doesn't need to be 100%accurate, just the change in resistance will matter. I'm doing it this way because i remember somewhere on the internet they sold a gsr detector that used an rc circuit, and i was like, hey, why not give it a go? The site
http://www.robotshop.ca/PDF/RCtime_App_Note.pdf
has some good data on measuring resistance using rc circuit. In actuallity, it looks pretty accurate, assuming the capacitor doesn't drift in capacitance (which it does, but as i said, this doesn't matter, because only the change in resistance matters).
I've noticed no-one has been responding, I guess they're waiting for a little success to start the flood of responses

Till then!

**Placebo** · 02-12-2008 07:03 AM

The piezo sensors rely on having a face mask again, which I'm not keen on.
But if it's got reliable results and isn't too hard to make ... hmm... might be a good idea.

**ethan_hines** · 06-21-2009 12:27 AM

To whom it may concern, I've been looking at alternative ways to detect rem sleep other then using IR goggles and I think this maybe it. It's a "Neural Impulse Activator" believe it or not it's used as a gaming device to control movement with brain waves. It's an electro-myogram, electro-encephalogram, and electro-oculogram all-in-one. I'm not an expert in electronics But I think this is something to look into and it's relatively inexpensive I found Amazon selling it for about eighty five dollars. It would obviously need some tinkering but it basically should do the trick. Please let me know what you think. I should mention that this is not my idea but an Idea I found on the fourm at this website:http://www.ocztechnology.com/product...pulse_actuator

**marcc** · 06-26-2009 06:50 AM

It's probably easier to graph one night's sleep and work using a timing device to set off in REM

But I'd love to see a cheap REM detector

Side-note: I have a small heart beat monitor that you just clamp onto your thumb. It has a 3.55mm audio-like output jack, and I was wondering if there were any way to hack this up? Thanks

**ethan_hines** · 07-06-2009 09:51 PM

Originally Posted by Durett

.... i remember somewhere on the internet they sold a gsr detector that used an rc circuit, and i was like, hey, why not give it a go? The site
http://www.robotshop.ca/PDF/RCtime_App_Note.pdf

I just want to make sure...rc in this case doesn't mean Reality Check right?

Originally Posted by davidcaudron

Here is the kind of sensor i am talking about:
http://www.meas-spec.com/advizia/v41...=Piezo&Rnd=124

Just for fun I thought I'd check into these sensors so I emailed the company and sure enough they sent 4 piezo sensors to me in the mail.

**coconuta2** · 09-03-2009 10:33 AM

So, I've had this Nova Dream maker for about 8 mos. I used it every night for about 2 mos. I received nothing. It ends up on the side of my bed or falls to the floor. It's supposed to detect REM and other light sources in my room. It rarely does that. I set it and I even spoke with that Bruce guy. All I want it to do is blink maybe a few times every minute or every other minute. But it's just set to this REM detection mode. I notice that when I hear sounds or flashing lights, sometimes they spill into my dream. That's when I realize that I'm dreaming. Can someone help me set my Nova dreamer other I'm just gonna give up on it and slang it on Ebay. Or, if someone knows of another technology that can aid in Lucid dreaming? I would forever be in debt to you.

Thank you kindly,

Carlos

**ethan_hines** · 09-03-2009 03:46 PM

Originally Posted by coconuta2

So, I've had this Nova Dream maker for about 8 mos. I used it every night for about 2 mos. I received nothing. It ends up on the side of my bed or falls to the floor. It's supposed to detect REM and other light sources in my room. It rarely does that. I set it and I even spoke with that Bruce guy. All I want it to do is blink maybe a few times every minute or every other minute. But it's just set to this REM detection mode. I notice that when I hear sounds or flashing lights, sometimes they spill into my dream. That's when I realize that I'm dreaming. Can someone help me set my Nova dreamer other I'm just gonna give up on it and slang it on Ebay. Or, if someone knows of another technology that can aid in Lucid dreaming? I would forever be in debt to you.

Thank you kindly,

Carlos

Carlos, It's doing what it's supostodo.That is detect when your eyes are rapidly moving (REM) when you are dreaming, blink or make a noise (or both) and alert you in your dream that you are dreaming without waking you up.

**coconuta2** · 09-03-2009 05:02 PM

Thanks for the reply. I know that that's what it's supposed to do but that method doesn't work for me. I was just looking for some continuous blink or noise method that would work without it having to detect REM. I have to literally look up and down for like 10 secs for it to turn on. I know I don't sleep like that. It sounds simple enough but I don't know how to program it that way.

**ethan_hines** · 09-04-2009 11:51 PM

You might have to turn up the sensitivity. Depending on the model there are small adjustable potentiometers that just the sensitivity of the eye movement.

**chimpboysteve** · 01-28-2010 11:24 PM

I've just been reading an interesting experiment a guy is doing at the moment using a Neural Impulse Actuator (NIA) to detect REM. By the looks of it he left for Army Service. He developed some software to pick up on the REM but unfortunately needs a lot of work and is awaiting the Software Developers Kit to be launched to proceed his development.

It looks very interesting hopefully he will complete this soon.

Looks like it could work.

The link to the discussion is below:-

http://www.ocztechnologyforum.com/fo...and-brainwaves

Found these other links on the Forums:-
Here's another project using NIA with LED'S

http://www.ocztechnologyforum.com/fo...-Dream-Project

REM Detector that sends Tweets on Twitter when you REM

http://www.ocztechnologyforum.com/fo...ms-a-pynia-App

**Dylan Tinning** · 02-06-2010 11:27 AM

Wow this is a realy interesting thread and i hope people continue to try to make this device...

Well im only 16 and i am very interested in making a cheap novadreamer like device because the new Novadreamer 2 is said to cost between $800 to $1000... who would pay that?

Anyway im not very "smart" when it comes to most of these things but i will help anyway i can if its still going ahead... i do have some conections

**ethan_hines** · 03-08-2010 04:23 PM

This thread is like 9 pages long and I don't have the time or energy to leaf through it so can someone give me an update on what is the general concensious on how to best detect REM? Is it

IR
EMG
Skin Galvanic Response
EEG
Other

**Dylan Tinning** · 03-10-2010 01:31 PM

Im not sure but it doesn't look like any1 else is posting unfortunatly :/ This would be a very interesting thread to continue!

To answer your question out of my knowledge

I think i read somewhere that the skin response was a real good way of detecting REM... Thats just my knowledge

Please someone else post to continue this thread!!!

**ethan_hines** · 03-10-2010 05:58 PM

What about respiration frequency I heard that changes dramaticaly with REM

**Dylan Tinning** · 03-11-2010 01:36 PM

Well i suppose it all comes down to how "exciting" your dreams are???
It could be a really "boring" dream therefore having a low respiration frequency...

Like new people with LDing normally with there first LD its a very short one and they get woken from excitement so theres would be high, but experienced people would have a low wouldn't they???

Dunno just throwing things out there

**knacko** · 04-01-2010 11:30 PM

I am amazed by you guys. Crazy persistence in your undertaking. I respect that very much! I have two suggestions that could be useful.

First one is the cheaper solution. The openEEG project @ http://openeeg.sourceforge.net/doc/. It is a guy in Bulgaria (Europe) that is giving instructions to how to make an assembly of a 4 channel EEG.

Second suggestion is rather expensive but seems to be a stable device that came out recently. It is called Emotiv and can be found @ http://www.emotiv.com/

**Hijo de la Luna** · 04-02-2010 12:42 AM

In my personal research I have heard that the galvonic skin response is a poor detector of REM as the skin loses conductivity in sleep.

In my personal experience when I am doing WILD or OBE the first big sign I am asleep is when I my breathing changes. It becomes shallow, my expiration gets slightly longer, my inhalation is shallow and quick. Other than that I might begin to snore.

Rapid Eye MOVEMENT. I mean no sarcasm here but this phenomenon is a movement that is perceivable by the human eye to the awake person. so I think usinig motion sensors would be best.

It is true that respiration and heart beat increase in relationship to the dream content but it is mitigated. EEG measures brainwaves not experience. However if you were to corralate the relationship of the respiration cycle/heart rate with the sleep cycle maybe you could extrapolate that data to locate an REM cycle

You can be in theta without dreaming. To learn more about this Anna Wise has a great book calledThe High Performance Mind, which I highly recommend. It has to do with brain states and the recorded experiences in each state and, how we can create the brain state at will to suite our desired results or task.

BTW that website is overwhelming but interesting. I couldn't figure out where to start

**topcat** · 05-25-2010 12:36 AM

The rabbit hole goes deeper: 'Multi-Player Dream Games' in: http://www.dreaminglucid.com/issues/LDE%2054.pdf

**Teblin** · 05-30-2010 11:32 PM

Placebo I found a device not long ago on the internet called an OCZ NIA its a headbad that u could quite easily sleep wearing and it can detect alpha/beta waves muscle movement and lateral eye movement they cost around £85. The plug into computer via usb and come with calibration software and software that allows u to map ur brains events into emulated keyboard keypresses eg u could have 1 key press for looking right and another for looking left. The OCZ NIA is origanlaly aimed at gamers but you could quite easily detect these keypresses in another custom made program and then send out messages like "you are dreaming" or something to some small in-ear earphones that u also wear while you are asleep or something. I beleve alpha and beta waves also change during different stages of sleep which may make detecting dreams more acurate with some experimentation.