Randy Boulter | 1 Jun 2006 01:08

Re: [EE] Methods for tracking finger position

Forgive me for not providing a more complete description.  The intended
applicaton is a type of "virtual keyboard".  For now, I need to simulate,
using a finger-mounted sensor, the action of reaching out and touching a key
with one finger.  And then be able to track the finger as it is lifted and
moved to another key. This will eventually be expanded to 10 fingers.   I
located some information on the sensors you mentioned - these could be used
to determine if the finger is bent (i.e pressing a key), but that still
leaves the problem of locating the finger in space.  BTW, $6-12 per finger
is not a show-stopper - I would just like to do it for less if possible.

Thanks,

Randy

> > I have been tasked with doing a conceptual design for a device
> >  that tracks finger movement using a sensor device mounted to
> > the finger.  Does anyone have experience with this or something
> > similar?  Or thoughts or ideas?  For now, I only have to worry
> > about one finger - but need to track position in 3 dimensions
> > with a resolution of about 5mm over an area of 1 cubic meter.
> >  Also, the device cannot use a reflective method (such as ir or
> > ultrasonic).    So far, I have investigated using accelerometer
> > chips, but these are still fairly expensive and I would like a
> > lower-cost alternative.
>
> I'm not certain this is a feasible project within the parameters given.
> Particularly, the fact that you're feeling accelerometers are too
> costlly gives me pause.  If you can't handle US$6-12 per finger,
> which is the cost of many MEMS accelerometers these days, you
> are not likely to find a non-reflective method for tracking ten fingers
(Continue reading)

Zik Saleeba | 1 Jun 2006 01:17
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Re: [EE] Methods for tracking finger position

Look at the Nintendo Wii's controller. It uses an infrared LED in the
controller and for a base station has two cheap IR cameras a certain
distance apart. Position is read off the cameras and distance is
measured using triangulation. This method seems to give pretty
accurate absolute positioning for a very cheap price point.

Cheers,
Zik

On 01/06/06, Randy Boulter <wrb@...> wrote:
>
>
> I have been tasked with doing a conceptual design for a device that tracks finger movement using a sensor
device mounted to the finger.  Does anyone have experience with this or something similar?  Or thoughts or
ideas?  For now, I only have to worry about one finger - but need to track position in 3 dimensions with a
resolution of about 5mm over an area of 1 cubic meter.  Also, the device cannot use a reflective method (such
as ir or ultrasonic).    So far, I have investigated using accelerometer chips, but these are still fairly
expensive and I would like a lower-cost alternative.
>
> Thanks,
>
> Randy
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Gerhard Fiedler | 1 Jun 2006 01:18

Re: [OT] C Programming styles and guidelines

Marcel Birthelmer wrote:

> Don't forget about GNU indent, a code formatting tool. 

I'd say if the code is so bad that you have to run it through a formatter
to be able to read it, it shouldn't have been created under your
supervision :)

Seriously, I think that code formatting (at least the part that can be
fixed by a formatter) is one of the lesser important issues that should be
addressed in a good set of guidelines. 

Gerhard

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Gerhard Fiedler | 1 Jun 2006 01:24

Re: [OT] :Fwd: What is evil ? was: [OT] Who would you choose ?

Gus S Calabrese wrote:

> [ "If there has to be war", let everyone fully participate, children,  
> politicos, hot chicks, queers, babies, with phosphorous, rape,  
> torture, no rules, pulling out eyeballs, guns, dogs, knives,  
> fingernails, spitting, clawing,screaming ............  Maybe there  
> would be fewer advocates of war.   POD ]

Yes... I sometimes think whether the unwritten but seemingly effective
policy not to go after the highest leaders first (it's like they feel they
are all in the same boat :) is such a good one.

Gerhard

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Gerhard Fiedler | 1 Jun 2006 01:30

Re: [EE] Relay coil diode specifications

Vasile Surducan wrote:

> And the time when diode will switch, the voltage across it could be
> 
> u = L * di/dt
> 
> As long L is constant, t is direct dependent by switching time of
> diode but also by the transistor switching (that's why usually we
> choose a faster diode than 1N400x and not a standard lazy darlinghton
> but a switching transistor), [...]

How would a faster switching transistor reduce the voltage spike? Wouldn't
there be less of a spike with a slower transistor? In the extreme, if you
move the transistor slowly from on to off through its linear region, there
will be (almost) no spike at all. 

Gerhard

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brusque | 1 Jun 2006 01:46

[PIC] RTL8019AS problems, please help!

Hello,

     I'm working on a small board with a PIC18F4525-I/P and a RTL8019AS. 
Right now I'm only trying to make the communication work. The connection 
between the RTL and the PIC is identical to another board I have that is 
working ok.

     The fact is that it doesn't work. I'm noticed a very strange 
behaviour that I would like someone to told me if this is right or 
problematic. When the PIC sends data (PORTD) to RTL (SD0 to SD7) the 
waveform is the spected "square" waves. But, when the RTL is sending 
data to the PIC (PORTD pins are changed to input) there's slow risetimes 
of 1.2us and very fast falltimes (7.0ns, measured with a digital scope).

     Is this behaviour normal? I noticed that the other board (the 
working one) shows similar behaviour regarding the risetimes and falltimes.

     If you would like to see the schematic of the communication part of 
this board please take a look at 
http://brusque.dyndns.org:8080/temp/net_board.png.

     In fact there's not much thing besides communication, only some 
74HC595 latches and connectores.

     Thank you very much,

     Brusque
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Randy Boulter | 1 Jun 2006 01:43

Re: [EE] Methods for tracking finger position

> Sergey Dryga wrote:
>
> > Randy Boulter <wrb <at> isp.com> writes:
> >>
> >>I have been tasked with doing a conceptual design for a device that
tracks
> >
> > finger movement using a sensor
> >
> >>device mounted to the finger.  Does anyone have experience with this or
> >
> > something similar?  Or thoughts or
> >
> >>ideas?
> >
> >
> > How about using a (ultra)-sound source at the finger and 3 microphones
to
> > triangulate the position.  Something like this was used for DNA sequence
> > readout from autoradiographs using a pen as pointing device. The
resolution was
> > in sub-mm range (IIRC).
> >
> > Another option is to use 3 sound transducers and microphone on the
finger to
> > find position, similar to GPS, only with ultrasound.

Robert Rolf wrote :

> This method works quite well. We had an old 3-d digitizer that used
(Continue reading)

Gus S Calabrese | 1 Jun 2006 02:06

Re: [EE] Methods for tracking finger position

When you come up with a method for $12 per finger, let me know
I would love to help you test it.
POD
0000000000000000000000000000000000000000000000
On 2006-May 31, at 17:08hrs PM, Randy Boulter wrote:

Forgive me for not providing a more complete description.  The intended
applicaton is a type of "virtual keyboard".  For now, I need to  
simulate,
using a finger-mounted sensor, the action of reaching out and  
touching a key
with one finger.  And then be able to track the finger as it is  
lifted and
moved to another key. This will eventually be expanded to 10  
fingers.   I
located some information on the sensors you mentioned - these could  
be used
to determine if the finger is bent (i.e pressing a key), but that still
leaves the problem of locating the finger in space.  BTW, $6-12 per  
finger
is not a show-stopper - I would just like to do it for less if possible.

Thanks,

Randy

>> I have been tasked with doing a conceptual design for a device
>>  that tracks finger movement using a sensor device mounted to
>> the finger.  Does anyone have experience with this or something
>> similar?  Or thoughts or ideas?  For now, I only have to worry
(Continue reading)

Robert Rolf | 1 Jun 2006 02:43
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Picon
Favicon

Re: [EE] Methods for tracking finger position. Virtual keyboard already exists

Oh, you mean like this:
http://www.thinkgeek.com/computing/input/8193/   $180 US

"This tiny device laser-projects a keyboard on any flat
surface... you can then type away accompanied by simulated
key click sounds. It really is true future magic at its best."

company home page http://www.virtual-laser-keyboard.com/

or this one http://www.virtualdevices.net/

Guess they've already beaten you to market...
R

Gus S Calabrese wrote:
> When you come up with a method for $12 per finger, let me know
> I would love to help you test it.
> POD
> 0000000000000000000000000000000000000000000000
> On 2006-May 31, at 17:08hrs PM, Randy Boulter wrote:
> 
> Forgive me for not providing a more complete description.  The intended
> applicaton is a type of "virtual keyboard".  For now, I need to  
> simulate,
> using a finger-mounted sensor, the action of reaching out and  
> touching a key
> with one finger.  And then be able to track the finger as it is  
> lifted and
> moved to another key. This will eventually be expanded to 10  
> fingers.   I
(Continue reading)

Robert Rolf | 1 Jun 2006 02:47
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Picon
Favicon

Re: [EE] Methods for tracking finger position

Randy Boulter wrote:
> 
> Robert Rolf wrote :

>> We had an old 3-d digitizer that used
>>a pen that snapped (electric arc) and 3 mics with about a 0.5 meter
>>spacing, and it covered the 1/2 meter cube quite well.
>>
>>With 4 external sources, (to get better closure on the RMS position
>>error), and phase measurements, one could get very good accuracy,
>>if a continuos high sample rate was required.
>>
>>Sounds to me like you're looking to do performance art, so there is
>>no budget available to use the optimal technology.
>>
>>Robert
> 
> 
> This sounds like an excellent method, but how far apart would the
> microphones have to be if they were placed, say 20 feet away from the sound
> source (finger), and still maintain accuracy within a few millimeters?

First you say 1 meter (3 feet) and now you're asking for 20 feet.
BIG change in specifications here. Pointless for me to waste my time
suggesting solutions for a moving target.

The accuracy would be determined by noise levels, and how accurately
you measure the transit time.

Robert
(Continue reading)


Gmane