Stud Finder
Bean
Posts: 8,129
Has anyone attempted to build their own stud finder ?
From what I found on the net, it seems they work by measuring a capacitance change of metal plates in the sensor.
I was wondering if you could use ultrasonics to sense thickness ?
Bean.
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"Wise men know when they're right. The wisest also·know when they're wrong."
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From what I found on the net, it seems they work by measuring a capacitance change of metal plates in the sensor.
I was wondering if you could use ultrasonics to sense thickness ?
Bean.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"SX-Video·Module" Now available from Parallax for only $28.95
http://www.parallax.com/detail.asp?product_id=30012
"SX-Video OSD module" Now available from Parallax for only·$49.95
http://www.parallax.com/detail.asp?product_id=30015
Product web site: www.sxvm.com
"Wise men know when they're right. The wisest also·know when they're wrong."
·
Comments
If you turn on teh stud finder and THEN put it towards a wall, it will start beeping because of the wall triggering it.
If you put it against the wall and THEN turn it on, it will calibrate itself there and then when you pass over a stud (not myself) it will beep.
I don't know if this is a capacitance thing or not....could understand it with metal studs, but wood ones? I honestly don't know!
So, maybe an ultrasonic would work. But the trick is not letting it triggeron the wall in front of you. What's the "blanking distance" with the typical ultrasonics (or ping for instance)?
In our radars there is a time interval where there is still high amounts of energy in the waveguide...if we were to turn on our receivers, they'd blow. So we use a TR Limiter (a small cell in the receiver path that has radioactive gas in it that ionizes with high amounts of energy which blocks the energy from passing through....when the energy level goes down, it opens up and lets the received signal from clouds and such, get through).....the transition time of this TR cell means we can't receive any information for a few useconds which equates to us being blind for the first 5km's around the radar.
(sorry...big ramble there)....
So, if the ping did turn on its receiver fast enough, your ultrasonic signal would be past the depth of the stud....
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Steve
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
Finding studs is a daily problem for me.
I have a stud finder, and was looking forward to opening it up with a hammer to see if I could give you some information on what does not work Unfortunately, I found a screw that once removed allowed the cover to be lifted without any gratifying carnage.
The unit is supposed to find studs, metal and AC power. It does reasonably locate metal and ac power. A slide switch selects either metal and AC, or studs. Leds light to indicate what has been found.
The sensing (or in this case, the non-sensing) part is a couple of windings on a ferrite core. One of the windings must be for the AC and metal detection. When (AC and metal detection) selected, my somewhat questionable homebuilt scope indicates the coil being driven at around 250kHz.
I cannot detect any signal going to the other coil when stud is selected. However, the unit does emit random annoying squeals from it's indicatory pizo.
If you want this one, I am happy to post it to you. If you can make something that actually works, I'll buy one.
bongo
Having earned a Journeyman Carpenter's card, I generally tap, listen, and test drill with a small bit. And, I usually drill my holes every 1" so that I locate the center of the stud. In this way, I don't get a mirror crashing off the wall because I was a bit to the left or the right.
Maybe you can figure out an ultrasound device that is more reliable. Or combine the metal detection and the ultra sound in a way that they agree.
Also, people often expect a stud every 16" or 24" in accordance with good construction. In remodeling, you can never be sure. So I usually do my drilling much lower than eye level - about knee high. In that way, people don't notice marks, touch-ups, and patches.
There are a lot of varibables.· Sometimes a building will call for 3-hour firewall, so the builder will use 3 layers of 5/8" sheetrock.· Obviously, that will not sound as hollow as one layer.· Plaster is quite different too.· And sometime people just glue a layer of sheetrock onto an existing concrete wall or concrete blockwall.
While I can look at the context and pretty well guess what was done, a device cannot handle 'human creativity'.· It has to rely on some assumptions about consistency.
It would be wonderful to be able to separate detection of household wire from water pipe.· Drilling into both can be a disaster.· Obviously the 110/220VAC is more of a hazard, so detection of a 50/60 cycle hum would be great and maybe worth more than a Stud Detector.· IN MANY CASES, THE HOT WIRE IS RUNNING PARALLEL TO ONE SIDE OF A STUD.
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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)
······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
Post Edited (Kramer) : 3/18/2006 8:55:59 AM GMT
Some ARRL books for Hams just had people using a coil of wire on the end of a coat hanger that was slightly amp'd and sent to a speaker/headphones.
At work we use these types of devices: www.lashen.com/vendors/triplett/fox_hound.asp
You have a 'sender' unit that puts on a 1kHz signal on a line and you use the inductive pickup to sense that line from a rats nest of other lines. Handy for sure!
But the inductive pickup in this thing also picks up 60Hz lines. The bigger the power cable, the more it hums along!
Now, put 3layers of sheetrock up and I don't know if this guy will still pick it up....but a nice little hack and mod might allow you to increase its sensitivity.
As far as detecting wood studs....my guess is that the wood still disturbs the magnetic fields; although obviously not as much as metal....so they're still detectable!
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Steve
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
As far as detecting AC power, doesn't the wire HAVE to be powering something ? Since the magnetic field is proportional to the current flow ?
I also use the "tap" method, I was figuring there must be an electronic way of doing the same thing ?
Bean.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"SX-Video·Module" Now available from Parallax for only $28.95
http://www.parallax.com/detail.asp?product_id=30012
"SX-Video OSD module" Now available from Parallax for only·$49.95
http://www.parallax.com/detail.asp?product_id=30015
Product web site: www.sxvm.com
"Wise men know when they're right. The wisest also·know when they're wrong."
·
Heres the page I found, it has links to patents covering the details of how they work: http://home.howstuffworks.com/question271.htm·, the second patent is the one Im talking about, If you want the full patent goto http://patft.uspto.gov/netahtml/srchnum.htm·and type the number in, no need to pay a second hand patent vendor when the source gives it away for free.
The newest technique is using radar to detect cavitation, a technique borrow from geological surveying.
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Post Edited (Paul Baker) : 3/18/2006 4:31:22 PM GMT
And the capacitance device is apparently driven by a lowly 556!
Is it really fair to use patent searches? After all, I have never seen this 'on the market'.
Contruction supply houses do routinely care metal detectors though as they are multi-purpose.
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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)
······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
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·1+1=10
Post Edited (Paul Baker) : 3/19/2006 5:18:58 PM GMT