Proximity Control and the Ghost Dance

[soggybag]

Looks like Transmogrifox made a proximity detector and posted to the old forum about it.
http://www.diystompboxes.com/sboxforum/viewtopic.php?p=120118&sid=d5297874045229d24b18bc45f24aa271
This schematic shows a proximity controled oscillator. But, a note on the page says something about using a 4046 PLL to generate a control voltage.
http://www.geocities.com/transmogrifox/ProxyOzzi.html
After searching the internet I found a site with a lot to say about PLLs.
http://www.uoguelph.ca/~antoon/gadgets/pll/pll.html
This page seems to say that the phase detector and loop filter outputs a DC voltage based on the difference between the frequency of the signal going into the phase detector and the frequency of the VCO in the PLL.

Am I understanding this correctly?

[The Tone God]

This page seems to say that the phase detector and loop filter outputs a DC voltage based on the difference between the frequency of the signal going into the phase detector and the frequency of the VCO in the PLL.

Am I understanding this correctly?

I belive the idea transmogrifox was getting at was to tune the PLL to the same frequency as the other oscilator from the opamp circuit thus when ever you came near the plate the PLL would detected the change in the opamp osc. frequency and output the difference as a voltage. Another approach but tuning that sucker must be hard and it would be sensative to it's enviroment. I have seen similar PLL based circuits. I wasn't too impressed. Its not that much different then the common dual clock circuit. I've seen other variations that use freq-to-voltage converters.

As always you can give it a try.

Andrew