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Proximity sensor
Proximity sensor
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Old 29th October 2007, 11:14 PM   #11
DWBH is offline DWBH  Portugal
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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 :P)

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?
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Old 29th October 2007, 11:49 PM   #12
BWRX is offline BWRX  United States
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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.
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Old 30th October 2007, 09:42 PM   #13
Pjotr is offline Pjotr
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FWIW

http://www.freescale.com/webapp/sps/...eId=0112698268

Cheers
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Old 31st October 2007, 11:33 PM   #14
DWBH is offline DWBH  Portugal
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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.
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Old 1st November 2007, 11:19 AM   #15
DWBH is offline DWBH  Portugal
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CORRECTION TO PREVIOUS POST: it uses a CD4093/CD4011, we're not sure yet.
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Old 4th November 2007, 07:11 PM   #16
micas is offline micas  Portugal
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Default Sensor Topiccione

I make ....
Click the image to open in full size.

Click the image to open in full size.

LED and LDR diy...
Click the image to open in full size.

Enjoy
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Old 5th November 2007, 03:46 PM   #17
ZAP101 is offline ZAP101  United States
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Default 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.../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
Attached Files
File Type: pdf an1903.pdf (49.4 KB, 81 views)
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Old 6th November 2007, 03:04 AM   #18
micas is offline micas  Portugal
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Default 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!
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Old 6th November 2007, 02:15 PM   #19
ZAP101 is offline ZAP101  United States
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Default Hey mica!!!

Hey that looks sweet...Got a schematic for it...I watched the video samps on youtube...Got Schematic???
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Old 6th November 2007, 09:25 PM   #20
micas is offline micas  Portugal
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Default Proximity Sensor Schematic

Hi Zap

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

Copyright Site.... http://topopiccione.atspace.com/PJ16...ibleTouch.html


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

The Schematic is this:
Click the image to open in full size.

and my PCB

Click the image to open in full size.

Click the image to open in full size.

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
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