Those 'antennae' don't *quite* (wincing in agonizing pain now as an RF-head) as actual antennas - capacitive probes: yes! Thanks for the info though. Jim ----- Original Message ----- From: "David P. Harris" To: Sent: Monday, February 18, 2002 2:49 PM Subject: [PIC]: How does a wall "Stud Finder" work? > There's a great one on the web-- consists of a 555 timer with an antennae > feeding a PIC (So I can change the header!). The PIC calibrates to teh freqy > when you turn it on, then reports changes in the freqy. I have a bookmark > somewhere...if anyone wants it. > David > > Jim wrote: > > > These 'stud finders' actually find studs - they > > work on the principle that a piece of drywall > > with a stud it behind presents a much different > > dielectric constant than a piece of drywall > > without dry wood behind it. > > > > An oscillator is constructed such that at least > > some portion of both plates of a capacitor that > > comprise part of a tuned circuit are presented > > to the wall. > > > > A 'reference null' is established first on a > > piece of drywall that does not have wood > > behind it - then a search for a stud can > > commence. > > > > Jim > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.