Mechanical Virtual Theremin

A Hall Effect sensor can detect PM fields. But for typical permanent magnets, I don't know if their range will be as great as that of an actual theremin (maybe a few inches). But why not use a capacitive effect (like an actual Theremin uses)? You could use that as an input to the 'virtual Theremin' if you wanted to. If you don't want to duplicate the non contact feature of a Theremin, just use a joystick.

BTW, isn't a "Mechanical Theremin" just a trombone?

Ha! My nomenclature is weak. If I described it as an analog GUI for audio, I'd be even less accurate.

My goal is to use 2 sensors perpendicularly mounted so that an object will be sensed by both simultaneously. This would enable it to be played "one handed".

Hello Stumpy,

Capacitive sensors as Paul mentioned can do that. Mount one below and one on the side.

Regards, Joerg

Nah, that's an acoustic Theremin. :)

Or whistling (which a Theremin is often compared to).

Tim

I did this with two LDRs for a toy application.

The original Theremin had to have the two capacitive sensors separated by some distance so they didn't interfere with each other. That's why I thought a sensor that responds to a discrete object would be preferable.

Using a light source or shadows?

This might be overkill:

-- Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com

------------------------------------------------------------------ In the beginning, there was nothing. And God said, "Let there be Light." And there was still nothing, but you could see it.

Looks expensive. I don't even know what I'd do with the 3rd dimension. Z axis = tremolo?

I'm in over my head, but will check out which of these might work.

Anybody remember the "Lumemin"?

The page shows a schematic of a toob-type Theremin, but the article was about using LDRs or something, which is where the "lume" comes from.

I'd think that the two antennas might not interact very much if they're at different frequencies that aren't harmonically related.

Good Luck! Rich

As someone posted earlier, It will be very difficult to sense distance more than just a few inches with any magnetic sensor. You could very well get into a situation where stray magnetic fields will dominate your signals. IMHO you would be much better off trying 2 modulated RF,light, or ultrasonic sources tuned to 2 different frequencies. It would seem that the major problem with one handed operation will be involve overcoming the problem of sensing the hand broadside and edgewise, since edgewise presents a much smaller profile to sense. This seems to be especially true when trying to minimize interaction between the 2 axes of motion. As usual, I could be wrong.

Mike

Earlier I had indicated that a permanent magnet would be the object sensed. I could hold it or mount it on a stick and wave it about like a mad conductor. I'm still presuming that a Hall Effect sensor would work with a strong enough magnet. I suppose a battery powered electromagnet is not out of the question. Don't want it to look like a cattle prod and scare the audience.

There's 6 degrees of freedom if you count the angular measurements. Like I said, overkill.

On the other hand, add a couple of VR gloves and you can make an air guitar. ;-)

I hate to sound like a pesimist, but another problem with using a permenant magnet will be the orientation of the magnet relative to the sensors. The analog hall sensors that I have worked with are ratiometric with the output sitting at VCC/2 with no field present and goes up or down depending on field polarity, I.E. north or south pole facing the sensor. How far it moves up or down is determined by the field strength. I don't think you realize just how small the signal will be with even a very strong magnet. I'm sure these problems can be overcome, but I sure wouldn't want to tackle it.

Mike

I hear what you're saying. Time for me to stop talking and go away and get some work done. The polarity issue would mean that rotating the magnet in place would vary tone and volume .:. reproducibility would be challenging.