Ultra-simple DIY capacitive absolute 3D position sensor

[geekmaster]

While waiting for your Leap Motion sensor, here is an ultra-simple DIY capacitive 3D sensor:

[youtube-hd]http://www.youtube.com/watch?&v=ikD_3Vemkf0[/youtube-hd]

I plan to try this soon. It may block your view with multiple LCD panels (like I have), but should work reasonable well with an HMD like the Rift, or with a laptop as shown in the video. With a pair of these 3D sensors, you could use both hands in 3D space.

A cardboard and tinfoil sensor like this would fit right in with the cardboard-framed DIY Rift clones some of us have.

Build instructions can be found at Make!
http://makeprojects.com/Project/A-Touch ... face/2233/

[virror]

Very cool, so simple and so very obvious design when you see it, amazed that no one has come up with this idea earlier.

Edit: Next step is to dress your room in foil and do positional tracking? : D

[MSat]

Pretty slick, though it would probably be limited in its accuracy as it could only couple to the entire mass of the object in its field. So pointing with your finger may be a no go unless you create one small enough for just a finger. I suppose another option would be to break each capacitor plane into smaller ones similar to how capacitive touch screens work, but then again, you probably wouldn't need multiple planes. Still, it's pretty awesome in its simplicity. If you substitute foil for a translucent conductive film, you could place it in front of your monitor without obstructing it.

[geekmaster]

... Edit: Next step is to dress your room in foil and do positional tracking? : D

I thought of that too (obvious next step), but using a top plate on the ceiling instead of a bottom plate (to detect crouching).

You may need to remove all electrically-grounded (or large metallic) objects from the vicinity (including BEHIND the capacitive plates), which may include house electrical wiring and metallic (or water-filled) plumbing, or they could have a bigger influence on positional readings than you poor little body. Perhaps that could be overcome with tuned RF sensing (grid-dip effect)?

But it is still worth giving it a try. It might just work even with nearby wiring behind the capacitive wall plates.

[geekmaster]

... So pointing with your finger may be a no go unless you create one small enough for just a finger. ...

Perhaps you could point with greater accuracy with a conductive stylus like you can buy for capacitive touchscreens. It is worth a try...

[Dakor]

hm.. i'm wondering if I can rewrite the software to work with the GPIO's of my raspberry pi..
I didn't read any input beside on and off yet (right now I use the GPIO pins to control my remote-sockets and I did not have the time to look further into it)

But this is great looking forward build one after my exams !

[MSat]

... So pointing with your finger may be a no go unless you create one small enough for just a finger. ...

Perhaps you could point with greater accuracy with a conductive stylus like you can buy for capacitive touchscreens. It is worth a try...

Should work, but probably if it's the only object that can be capacitively coupled in the field.

[geekmaster]

hm.. i'm wondering if I can rewrite the software to work with the GPIO's of my raspberry pi..
I didn't read any input beside on and off yet (right now I use the GPIO pins to control my remote-sockets and I did not have the time to look further into it)

But this is great looking forward build one after my exams !

Should be doable. The software works basically the same as the old-school analog joystick drivers (which timed how long it took to charge/discharge capacitors controlled by the joystick potentiometers). The capacitor was in the joystick interface (typically built into a sound card), instead of being in the sensor plates as used here. Here is an Arduino example with code:
http://arduino.cc/forum/index.php/topic,16030.0.html

A similar method is also used to read the amount of light hitting an LED. When you reverse bias an LED, it becomes a small capacitor, and to read it you just charge it and then measure how long it takes light to discharge it via photosensitive electron leakage. Here is an Arduino example with code:
http://playground.arduino.cc/Learning/LEDSensor

All of these things use a similar method of measuring charge stored on a capacitor using only a digital input, so you may be able to reference code for any of these things. Google finds mostly Arduino examples, rather than Rapberry Pi, so you may need to adapt them...

[geekmaster]

Perhaps you could point with greater accuracy with a conductive stylus like you can buy for capacitive touchscreens. It is worth a try...

Should work, but probably if it's the only object that can be capacitively coupled in the field.

To use two hands, you would need two of these sensors (one on each side of your monitor). I would probably use foot switches to grasp objects in 3-space (or perhaps you could just hold a switch in your hand inside the sensor cube).