Inductor question 2

I would like to build a circuit which uses a variable inductor as the input to set some states for output out of a micro. I was figuring I'd use an A/D channel on a cheap micro and output based on the input (the inductor). But I don't really know how to set up the inductor for this purpose. If the inductor is tuned one way, I'd like the A/D to get X counts and as you tune the other way you'd pass through a couple states and end up with the full range rail voltage at the other end (so like 5v would be 1 state 2.5v another and 0v another). I think I could do this with resistor networks, but I want to use an inductor for what I'd like to build. Can anyone suggest a relatively cheap circuit which can use the inductor as the input. I can input a square wave to the inductor with a 555.. though.. I'm not sure if that would work. Since a DC voltage would just be just a short -- I'm not sure how to set up the inductor as the input.

If you use an air core inductor with a movable iron slug, you will get a variable inductor. If the value of inductance is between 0.5uH and 50uH, you can use a circuit like this to find the inductance (view in fixed font or M$ Notepad):

Q and D Inductance Tester .---. 3K9 | | ___ _V_ | |\ ___ .--|___|--|___|-o----|H>O-|___|--. | 2K 10 turn |/ 330R | | | | | |\ | |\ ___ | o------|H>O-----o----|H>O-|___|- o | |/ | |/ 330R | --- | | Output --- 1000pF | |\ ___ | |\ |\ ___ 10mV/uH | '----|H>O-|___|- o-|H>O--|H>O-|___|-o---o | |/ 330R | |/ |/ 39K | + === | --- GND o --- | |0.33uF C| | Lx C| | - C| o---o | | o | | | === === GND GND created by Andy´s ASCII-Circuit v1.24.140803 Beta

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The circuit, which is a mod of an ARRL circuit published a few years back, is described at:

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You can place an op amp at the output of this circuit to amplify to full scale output as desired. If your inductance is higher, you can play with the R and C values to get a wider range.

Good luck Chris