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DWBH 22nd October 2007 08:39 PM

Proximity sensor
I'm not sure whether I'm in the right forum (sub-forum, whatever).
So, I've been looking for a Proximity Sensor. Yeah, that's right.
I've searched for patents, google, google images, other sites... but nothing is 100% what I want - and by this, I don't mean it sucks/it can't be adapted.

But basically, I'm looking for some kind of proximity sensing device (call it what you want) that has an antenna (copper plate, for e.g.) and a CV out. That's what I want. For instance, when I put my hand over the plate and approximate my hand towards the antenna the led lits/dims... I'm going to use this CV out not to control a LED, but to drive a optocoupler, which will replace a pot on a audio circuit. Getting so far? It'll be this kind of theremin, but no theremin at all.... Look here:

I'm not sure if what I'm looking for is a capacitive sensor, or a inductive one, so I was kind of hoping you could help me out here.

I currently have this circuit populated and up and running
An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.

but it's a bit unstable, because it varies with temperature and

The problem with the Invisible Touch is that it works on the principal of using the body's capacitance to change the frequency of the oscillator. The human only has a certain range of capacitance so the oscillator must be tuned to pick up on that small range. The range required will put the oscillator into a high frequency which is nice as it will probably be less likely to leak into the audio but the universe has rules to play by. The higher frequency needed to sense the small capacitance generates a smaller sensing field. This smaller field is also prone to stray capacitances in the environment that are larger then that of the body and you would be surprised just how much there is.
by The Tone God

Can this one be modded?

The original (Zvex) is quite simple and I want something as simple as possible?

Can you help me fellows?

DWBH 24th October 2007 01:54 PM

bump? :(

I_Forgot 24th October 2007 10:05 PM

My son's Lego Mindstorms Robotics kit comes with an ultrasonic range sensor that can accurately tell distance from a few cm to several m away. Such a sensor could be adapted to almost any sort of analog control range you want. I have seen kits for similar ultrasonic rangefinders. Get one and modify it to do what you want.


DWBH 24th October 2007 10:38 PM

Thank you!! Finally, a response!

However, I don't want to buy any kits. I want to keep it as cheap as possible, so buying a kit is not something to have in mind.

These last days I've been looking also for IR proximity sensors. However, most of them act like on/off switches. But, what I want is something gradual, in which the voltage increases, as an object approaches. Not what those on/off switches do - no object 0V. object 5V.

BWRX 24th October 2007 10:48 PM

I would probably use a capacitive sensor. You could even design your own. There are chips out there designed to work with capacitive sensors. Search for PSoC from Cypress for one example.

I_Forgot 25th October 2007 01:22 AM

Have a look at this:

At $30 you'll have a hard time finding the parts for less, and it will save you many, many hours of labor.

Sometimes spending a few $ more for a kit that does most of what you need will turn a project into a reality instead of just another pile of notes in a notebook.


BWRX 25th October 2007 01:39 AM


Originally posted by I_Forgot
Have a look at this:

At $30 you'll have a hard time finding the parts for less, and it will save you many, many hours of labor.

No fooling! That thing looks pretty cool. Thanks for the link.

DWBH 28th October 2007 10:55 AM


I_Forgot 28th October 2007 06:16 PM

What don't you like about the circuit for the wah pedal? What are you trying to make?


I_Forgot 28th October 2007 07:41 PM

What is a "CV"?


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