Proximity sensor

[DWBH]

Hi.
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:http://www.zvex.com/wahprobe.html

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 was not working when we last tested it.

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]

bump?

 

[I_Forgot]

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.

I_F

 

[DWBH]

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]

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]

Have a look at this:
http://www.hobbyengineering.com/H1145.html

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.

I_F

 

[BWRX]

Have a look at this:
http://www.hobbyengineering.com/H1145.html

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]

bump

 

[I_Forgot]

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

I_F

 

[I_Forgot]

What is a "CV"?

I_F

 

[DWBH]

First of all, the circuit is ok, but it's rather unstable. It varies with temperature, and , for eg, I turned it on and I tune it. Them I switch it off and 5 minutes later I have to tune it again. The original circuit is also very simple, much simple, compared to this one and is stable as a table. I want one like that. On this other forum, we're trying to reverse engineer it, if we get to some conclusion I'll post it here (the conclusion, not the schem )

Ahh, CV is Control Voltage. The theremin/controller circuit has to have a CV out (control voltage out). Then, the other circuit (audio - in this case, a wah circuit), has a pot. We substitute that pot with a LDR and connect a LED to the CV out of the theremin circuit. Together, the LED+LDR make a optocoupler (vactrol).

As I approach my hand to the antenna of the theremin, voltage increases, driving the LED. The LDR reacts to the light emmitted and therefore augments its resistence (or diminishes it) and acts like a potentiometer.

Btw, do you say antenna or antennae?

 

[BWRX]

Feed a high frequency square wave into an RC lowpass filter, where R is a fixed value and C is the capacitance of the proximity sensor. AND the output of the lowpass filter with the original PWM signal and the result is a square wave with a duty cycle that varies with the capacitance of the proximity sensor. Use an op amp to buffer and lowpass filter the output PWM signal and you now have a DC signal (your "CV") that varies with capacitance. That's one of the simplest ways to do it.

Antennae is the plural form of antenna.

 

[Pjotr]

FWIW

http://www.freescale.com/webapp/sps/site/taxonomy.jsp?nodeId=0112698268

Cheers

 

[DWBH]

News!

I already have the circuit but it is not verified yet (we're in the middle of that process). But, I can tell you that it only uses a CD4093 a transistor and the rest are passive components.

 

[DWBH]

CORRECTION TO PREVIOUS POST: it uses a CD4093/CD4011, we're not sure yet.

 

[micas]

Sensor Topiccione

I make ....

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

LED and LDR diy...

An externally hosted image should be here but it was not working when we last tested it.

Enjoy

 

[ZAP101]

Hey DWBH...check this out...

Hey DW,
after literally hundreds of attempts at building a foolproof prox sensor...I have found the following to be the best...
Go to http://www.maxim-ic.com/appnotes.cfm/appnote_number/1903/CMP/BTDT
the next best was using a fet input complementary output opamp...if you want I will hunt up the schem...and send it along...

P.S.
every one of the CMOS type prox dets that i tried SUCKED!

mike

 

[micas]

Sensor TOPICCIONE

No comment....

http://www.youtube.com/watch?v=9tWsBk0mWTc

Connection with another project (VU Resitor Meter)....

http://www.youtube.com/watch?v=L0-b5BhpQKU

Enjoy!

 

[ZAP101]

Hey mica!!!

Hey that looks sweet...Got a schematic for it...I watched the video samps on youtube...Got Schematic???

 

[micas]

Proximity Sensor Schematic

Hi Zap

...................................................................................
The Proximity Sensor
...................................................................................
Schematic ..... Invisible Touch! http://topopiccione.atspace.com/pjimages/TPCInvisibleTouch.sch.gif

Copyright Site.... http://topopiccione.atspace.com/PJ16TPCInvisibleTouch.html


..............................................................................
The VU_Resistor Leds
...............................................................................

The Schematic is this:

and my PCB

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

And .... the result: http://www.youtube.com/watch?v=3ef0d-csBgw

.............................................................................................

I connected both circuit, the sensor (width Led+Ldr) to VU_Led...


Enjoy
Regards