Stud finder design

[Freshwreckage]

Hey all...

I am current working on a project that will require and array of stud finders.
I am currently attempting to create a single stud finder and am getting hung up detecting the capacitance change. I have succeeded in creating a touch switch, but I am more interested in detecting the change in capacitance vie proximity instead.

Any help would be appreciated

 

[Sceadwian]

Don't most stud finders use audio signals not capacitance changes?

 

[RadioRon]

I thought they sense small changes in inductance.

 

[DigiTan]

My understanding was 2 charged plates used the wall as a dielectric, and the change would make that capacitor's oscillator drift. So you're probably looking at some kind of high-frequency oscillator and a high Q notch filter on the output. But this is 100% guesswork.

 

[Freshwreckage]

Everything I have seen uses the capacitance plate to spot the stud...

 

[DigiTan]

Yeah, they used to use a similar technique for portable doorknob alarms. You would slide it onto a metal knob and if anybody touched it from the opposite site, the capacitance change would mess up the oscillator's frequency and trigger an alert. Same basic principle. Different apparatus.

 

[hjames]

I think you're going to have to give us a bit more of a description of what you've built so far. Half-broken touch sensors are "easy" to construct, but if you're brand new driven-shield, synchronous demodulation sensor isn't working, we'll have some different suggestions for you.