# A thinking cap: Can this be done? For cheap?
**URL:** https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058
**Category:** Factual Questions
**Created:** [May 2, 2005, 3:45pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058 "2005-05-02T15:45:29Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@ReuvenB](https://boards.straightdope.com/u/ReuvenB)
#### Post date: [May 2, 2005, 3:45pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/1 "2005-05-02T15:45:29Z")
After my AP Physics exam, I’m going to have about a week and half of class left, with nothing to do.
So I’ve decided to look into building a simple device that wears like a hat, and the wearer can decide, using thought, to activate either red or green LEDs on the hat. I’m looking to do this for cheap, hopefully for less than $50, and requiring little time to assemble. I have about 10 hours to work on it before the end of school.
Is it possible? Does anyone have any experience doing this? Or is this merely the fevered dream of a madman?
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### Author:  [@CynicalGabe](https://boards.straightdope.com/u/CynicalGabe)
#### Post date: [May 2, 2005, 3:56pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/2 "2005-05-02T15:56:23Z")
Certainly, if you count using thought to move one of your hands to move a toggle switch.
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### Author:  [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)
#### Post date: [May 2, 2005, 3:58pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/3 "2005-05-02T15:58:30Z")
There’s nothing coming out of the brain that penetrates the skull, so you’re looking at minor brain surgery. Best to find another project.
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### Author:  [@Left\_Hand\_of\_Dorkness](https://boards.straightdope.com/u/Left_Hand_of_Dorkness)
#### Post date: [May 2, 2005, 4:04pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/4 "2005-05-02T16:04:25Z")
> [@ultrafilter](#):
>
> There’s nothing coming out of the brain that penetrates the skull, so you’re looking at minor brain surgery. Best to find another project.
I’m pretty sure you’re wrong on this: otherwise, there’d be no points to experiments in which sensors were hooked up to researcher’s foreheads to read brain activity during the experiment. I’ll see if i can find a cite on this unless someone beats me to it.
That said, I’ve got no idea how to build this cap.
Daniel
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### Author:  [@Joey\_P](https://boards.straightdope.com/u/Joey_P)
#### Post date: [May 2, 2005, 4:05pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/5 "2005-05-02T16:05:05Z")
Trepanning can certainly be done in less the 10 hours (and under $50, I’ve seen people do it with standard drill bits), any volunteers?
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### Author:  [@Nanoda](https://boards.straightdope.com/u/Nanoda)
#### Post date: [May 2, 2005, 4:35pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/6 "2005-05-02T16:35:25Z")
Geez people, your brain-PC interfaces sure aren’t working today.
I recall seeing early experiments of researchers guiding cursors and tilting airplane simulators at _least_ as far back as 5 years ago.
Given the proper Google search, you can see [recent research results](http://www.google.ca/search?hl=en&q=thought+interface+computer&btnG=Google+Search&meta=) in this field, though no schematics unfortunately.
Just 2 LEDs sounds fairly simple and possibly do-able with off-the-shelf components - I’m sure someone will be able to give you a basic idea of how this works and what parts you’d need.
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### Author:  [@EssOEss](https://boards.straightdope.com/u/EssOEss)
#### Post date: [May 2, 2005, 4:41pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/7 "2005-05-02T16:41:43Z")
Maybe just some motion sensors so that if you move your ears/forehead/whatever 1 time, it toggles red, 2 times, it toggles green 😃
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [May 2, 2005, 7:03pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/8 "2005-05-02T19:03:10Z")
Even assuming that you have sufficient resources to do this (I know it can be done, but I’ve no idea how difficult it is, or if it requires any specialized or expensive materials or components), it’s probably going to take some training. That is to say, you’re not going to be able to just think “red” and “green”. You’re going to need to alter your brain wave patterns in some way recognizable to the machine. Humans can do this voluntarily, but most of us don’t know how. The way to learn is to get some device which detects brain activity, and to just keep practicing.
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### Author:  [@Left\_Hand\_of\_Dorkness](https://boards.straightdope.com/u/Left_Hand_of_Dorkness)
#### Post date: [May 2, 2005, 7:09pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/9 "2005-05-02T19:09:54Z")
Okay, [the cite that there’s something “coming out of the brain that penetrates the skull”](http://www.stjohnsmercy.org/healthinfo/test/neuro/TP011.asp):
> [@](#):
>
> An electroencephalogram (EEG) detects abnormalities in the brain waves or electrical activity of the brain. During the procedure, electrodes consisting of small metal discs with thin wires are pasted on the scalp. The electrodes detect tiny electrical charges that result from the activity of the brain cells. The charges are amplified and appear as a graph on a computer screen or as a recording that may be printed out on paper. Your physician then interprets the reading.
One possible avenue to explore would be the wide world of biofeedback devices: while only the shmanciest ones purport to read brain activity (I’m nowhere near qualified enough to judge their claims), some of them purport to read stress levels through such avenues as pore dilation and such. Maybe you could make a stress cap, wherein the wearer thinks of homework and lights up the light?
Daniel
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### Author:  [@groman](https://boards.straightdope.com/u/groman)
#### Post date: [May 2, 2005, 9:10pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/10 "2005-05-02T21:10:30Z")
An easier device, albeit this would be cheating within your spec, would rely on the polarity of the eye to detect changes in the magnetic field, kind of like a face compas. that way you can detect very subtle eye movements, combined with how Mouse Gestures work, you could probably hook up a simple microcontroller to detect an “eye” gesture and do things.
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### Author:  [@Khadaji](https://boards.straightdope.com/u/Khadaji)
#### Post date: [May 2, 2005, 10:55pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/11 "2005-05-02T22:55:33Z")
[Here](http://www.medcompare.com/jumppage.asp?headerid=370) might be a place to start. It has some nifty things like _electrode head caps_ and _Biomedical Amplifiers_ and other good stuff. But I’m guessing that it costs a lot, since they don’t have prices on their site and instead have a link to request a quote.
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### Author:  [@DougC](https://boards.straightdope.com/u/DougC)
#### Post date: [May 2, 2005, 11:59pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/12 "2005-05-02T23:59:48Z")
-
-
- You can certainly build electrometers that can detect waves as low as brain-activity, but I don’t know of you can easily build anything that can _discriminate_ between one type or region of activity and another. It would seem to me that if such a thing were easily possible, fully-paralyzed people would want one really really bad. Since I have not heard of such a thing, I would suppose it is not easily possible.
- Here’s one cheapo-electrometer page, anyway: [http://amasci.com/electrom/sas51p1.html#electro](http://amasci.com/electrom/sas51p1.html#electro)
…scroll down about 1/3 to where it says “An Experimenter’s Electrometer”. You might still find some entertaining use anyway.
~
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### Author:  [@DougC](https://boards.straightdope.com/u/DougC)
#### Post date: [May 3, 2005, 12:07am UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/13 "2005-05-03T00:07:26Z")
—An _electrometer_ is a device for measuring either very small voltages, or very-low-current-draw voltages, such as static electricity (as noted in that page). So what you would do is build two or more electrometers, and then run a separate coil into each, to act as an antenna. I guess…
~
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### Author:  [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)
#### Post date: [May 3, 2005, 12:12am UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/14 "2005-05-03T00:12:59Z")
If you use basically the same idea as they use in biofeedback, it can be done. The cost would maybe be about $50, maybe a bit more, but it would take me longer than 10 hours to design the thing and I’ve got close to 20 years experience designing electronic stuff.
Your cost constraints are an order of magnitude off for what you would need to be able to buy something off the shelf, so you’ll need to make your own circuits. You are going to need a pretty low noise instrumentation amplifier. You can feed this into the A/D of a microcontroller and do all of the signal processing required in the microcontroller. Total cost should be somewhere in the $50 range. You are going to need to know how to design an instrumentation amplifier, and know a fair bit about digital signal processing. It would be a decently challenging project for a senior EE student, but I suspect it’s a bit beyond the skills of even a pretty sharp high school student.
Important note: Make sure this is battery powered and can NEVER NEVER NEVER be connected to AC current for power. An accidental short of AC through your head could be fatal.
On the other hand, if you can get creative and think of some way to activate a switch using the muscles on your head, you could pull this off for about $20 in parts.
You might also try shining a low power IR LED at your eye (mounted to a pair of glasses or something) and do a bit of signal processing on the reflection (IR detector, also mounted on the glasses, connected to a microcontroller for processing). You might be able to detect eye movement or blinking fairly cheaply.
10 hours just isn’t a lot of time.
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### Author:  [@antechinus](https://boards.straightdope.com/u/antechinus)
#### Post date: [May 3, 2005, 3:26am UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/15 "2005-05-03T03:26:13Z")
A mindswitch detects changes in brainwave patterns to determine logical state.
In [this work](http://www.science.uts.edu.au/research/mind_switch.html) a change from beta to alpha throws the switch.
It works, I have seen it in action.
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### Author:  [@audiobottle](https://boards.straightdope.com/u/audiobottle)
#### Post date: [May 3, 2005, 12:38pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/16 "2005-05-03T12:38:37Z")
I sort of work in a lab where we do some EEG stuff. In addition to what **engineer\_comp\_geek** said, you’ll also need to apply some nasty smelling gel to more effectively conduct your signals to your cap. It really is kind of gross and definitely not anything you’d want to have to constantly put on your head everytime you wanted to wear your hat out.
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### Author:  [@guizot](https://boards.straightdope.com/u/guizot)
#### Post date: [May 3, 2005, 12:51pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/17 "2005-05-03T12:51:04Z")
> [@XWalrus2](#):
>
> So I’ve decided to look into building a simple device that wears like a hat, and the wearer can decide, using thought, to activate either red or green LEDs on the hat. I’m looking to do this for cheap, hopefully for less than $50, and requiring little time to assemble. I have about 10 hours to work on it before the end of school.
Why do you want to do this, and why do you have to do it before the end of school?
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### Author:  [@ReuvenB](https://boards.straightdope.com/u/ReuvenB)
#### Post date: [May 3, 2005, 4:14pm UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/18 "2005-05-03T16:14:57Z")
> [@etmiller](#):
>
> Why do you want to do this, and why do you have to do it before the end of school?
Well, my teacher wants us to have something to do for the rest of the remaining class periods, and I thought that this would be an unbelievably cool thing to do.
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### Author:  [@clairobscur](https://boards.straightdope.com/u/clairobscur)
#### Post date: [May 4, 2005, 6:12am UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/19 "2005-05-04T06:12:23Z")
> [@DougC](#):
>
> It would seem to me that if such a thing were easily possible, fully-paralyzed people would want one really really bad. Since I have not heard of such a thing, I would suppose it is not easily possible.
>
> ~
Actually, it has been done. It’s used to move a cursor on a screen so that said paralyzed person can pick letters and “write” (the “guinea pigs” were people who couldn’t speak, either).
I assume that with the same system, the person could choose items from a menu and activate some computer controlled devices.
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### Author:  [@DougC](https://boards.straightdope.com/u/DougC)
#### Post date: [May 4, 2005, 10:48am UTC](https://boards.straightdope.com/t/a-thinking-cap-can-this-be-done-for-cheap/302058/20 "2005-05-04T10:48:55Z")
> [@](#):
>
> …Actually, it has been done…
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- Yea, but not in ten days on a shoestring budget. An MRI machine can detect locations of brain activity pretty well as I’ve read, but how much does a working MRI machine cost?
~
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