IR proximity sensor

[DWBH]

Hi y'all.
In search for capacitive proximity-sensors/theremins and such (looking for a alternative to the Invisible Touch), I thought about IR sensors.
One IR led and a phototransistor, an indicative LED and a couple more resistors and caps, and it's done. However, most of the circuits I've found work like on/off switches. Like the ones you find on those automatic doors (in the supermarket), and those hand dryers in public WC's.
However, in order to adapt it and put it in a stompbox, working as a Poorman's Wah Probe II, I'd need a gradual, or perhaps variable is a better word, IR proximity sensor. Most circuits are like:

• No object - 0V
• Object - 5V (or any other voltage)

But I want something like this:

• No object - 0V
• Object far - 1V
• Object getting closer - 2V
• Object getting even closer - 3V
• and so forth

Now, is it possible to mod one of those common IR proximity sensors, or more deep modifications are needed? Or perhaps, you may know of some circuit that works exactly the way I (we) want.
So, shoot!

[David]

Must your sensor be infrared?  If not, a Hall effect sensor could be just what the doctor ordered.

[DWBH]

What's that?

[chris_d]

Have you messed around with this sort of design yet?

http://www.diystompboxes.com/smfforum/index.php?topic=62070.0

It uses a pair of IR photoresistors coupled with a basic 555-based square wave oscillator for a theremin-like control vibe. You can get the transistors(actually the whole thing except for the vero board) from radioshack, and it is a pretty quick easy build that makes an interesting sound, which is shadow- and light- controlled...

Maybe check the link in that thread where the project came from if you haven't yet. That guy has a few interesting ideas for hands-free, theremin-like control.

-chris

[DWBH]

Yes, I've seen that.
But the problem is that that one has an output for a speaker, and not a variable voltage output. Also, it is sensible to room light, due to the usage of 2 phototransistors. This could be solved with a IR LED, which is less sensible to exterior lights.
Perhaps it's moddable, I guess.

[Paul Perry (Frostwave)]

The robotics boys use these Sharp modules: http://www.acroname.com/robotics/info/articles/sharp/sharp.html

[DWBH]

Must your sensor be infrared?  If not, a Hall effect sensor could be just what the doctor ordered.

No it doesn't. But, comparing to capacitive proximity sensors, I think that IR ones will be more stable, and will not pickup radio frequencies as capacitives do. I mean, there must be more advantages. And disadvantages.