Invisible "Air" control device?

[HankMcSpank]

Just wondering if anyone had dabbled with infra red sensors?

I'm looking to have a sensor which ultimately provides a DC voltage (representing how close the hand is placed to the sensor) that I can AtoD to extract the DC level/magnitude.

i don't want to use ultrasound as I'm toying with putting this on a guitar (& I'm worried about how wild string harmonics might interfere with an ultra sound sensor pickup - I remember jangling car keys & being able to change TV channels with an old TV that used ultra sound!)

But wrt using infra red...I'm thinking that it might be difficult to get a decent hand control 'range' going on - I'd like the 'range' to be about 8" (20cm) from the sensor.

Has anyone dabbled?

[Jerson]

I remember from way back when Robert A. Penfold had written some article in Practical Electronics Magazine about controlling the pitch of an instrument using hand movements. It wasn't using IR, but RF field modification by the moving hands. I cannot remember the exact name he used for it right now.

If you plan on using IR, Sharp has some sensors that could be useful. However, I am not really sure if they are the GO-NOGO type which work to a particular distance. One such sensor is the GP2Y0A02YK0F. It shows a range of 20-150cm and a nice curve to go along with it.

My hunch is you might be happier using near field RF for your application.

[HankMcSpank]

I remember from way back when Robert A. Penfold had written some article in Practical Electronics Magazine about controlling the pitch of an instrument using hand movements. It wasn't using IR, but RF field modification by the moving hands. I cannot remember the exact name he used for it right now.

If you plan on using IR, Sharp has some sensors that could be useful. However, I am not really sure if they are the GO-NOGO type which work to a particular distance. One such sensor is the GP2Y0A02YK0F. It shows a range of 20-150cm and a nice curve to go along with it.

My hunch is you might be happier using near field RF for your application.

Hi Jerson - Would you be thinking thinking of a theremin type device? http://en.wikipedia.org/wiki/Theremin (if so, since this is going on a guitar - having all that RF is probably not a good idea from an EMI pickup perspective)

Here's a chap that's used infra red (vs RF) to control a theremin....

http://bondoukousoftware.com/InfraredTheremin.html

with the obligatory video...

http://il.youtube.com/watch?v=-VFLlIj29CM

that 'control range' (3"?) in the video looks a little small for my needs.

He has a useful schematic at the foot of his page...which I guess is a good starting point - but I'd still like to get the range up a little.

[HankMcSpank]

It took a bit of Googling but the DIY robot community have come to the rescue...they're getting up to 30cm 'range'...

http://letsmakerobots.com/node/2907

[Jerson]

Yes of course. The theremin.

[aratti]

Have a look @ this link:
http://www.sparkfun.com/commerce/product_info.php?products_id=242

Cheers

Al.

[HankMcSpank]

Have a look @ this link:
http://www.sparkfun.com/commerce/product_info.php?products_id=242

Cheers

Al.


Many thanks Al - very interesting (though might be a bit obtrusive for where I'd like to put this - on a guitar)

[El_AMPo]

Already done it...

The best way to do it and get some range is with an infrared led and a REGULAR phototransistor (No dark/vis coating), and it's really cheap. (Sorry I'm not a fan of $10usd sensors + 30$ shipping)

On the detector part:
Drive the phototransistor between ground and with a 4K7 resistor to 5V and "tap" in the middle to get your ADC readings

On the emmiter part:
Pulse modulate the led to 1%-10% duty and calculate your current resistor to about 100ma (can be even more current, but stop torturing the poor thing), Don't forget a transistor driver for it.

On Software:
At the beginning of your code:
-Turn off the IR led, wait 500us, get an ADC capture
-Turn on the IR led and wait about 500us
-Get a second ADC capture, then turn off the IR led
-Store the differential as a "Initial calibration"
At the main loop:
-Turn off the IR led, wait 500us, get an ADC capture
-Turn on the IR led and wait about 500us
-Get a second ADC capture and then turn off the IR led
-Store the differential as a "Captured value"
-Get the differential between "initial calibration" and "captured value"

*Congratulations you got a value proportional to the distance of the reflected IR light

It needs some other filtering and maybe a linearization (because reflected light to the sensor is not lineal), but works really well in interior ambient light conditions (not daylight, too much IR) with a range of about 30-40cm even more if you don't need an extreme resolution.