Simplest PI detector possible?

[brucester]

cool, that solves that problem

thanks

[WM6]

Did u mean R9 and R10 to be 47k?

I tried those and they weren't as good as the original values.

Thanks. Another mistake. R10 have to be 62k.

[chemelec]

I have built this circuit up, Trying most of the variations shown here, But I am only getting a Detection Distance of 2 to 3 inches.
Definately not 8 inches or more.
Curious, What are other people here getting?

[brucester]

What size coil are you using?

I got 4.33 inches from a 3.9 inch coil. This was from a breadboard circuit, never bothered soldering it.

See videos on previous page for range test.

[chemelec]

Aproximately a 7 Inch coil, as was origionally shown.
I Can't watch Videos, as I am on SLOW Dial-Up internet.

[brucester]

Dial up? U live in a cabin in the rockies or something?

What opamp did you use? And what did you use for T2?

I will do a range test with a bigger coil when my copper wire arrives. But i assume it will be roughly equal to the diameter of a coil. Aluminium cans get twice the range of all other objects i found.

[chemelec]

Close, A little town (Hedley, B.C, Canada) of 210 houses in the Mountains, Just to the West Side of the Rockies.

Two TL081"s.
Even with a Large piece of metal, Only a Couple of Inches.

(Some of the Claims I read were a Mens ring at 8 Inches.)

[brucester]

Close, A little town (Hedley, B.C, Canada) of 210 houses in the Mountains, Just to the West Side of the Rockies.

Nice. Beautiful country.

(Some of the Claims I read were a Mens ring at 8 Inches.)

Yeah, either they are exaggerating, have a faulty sense of distance or that soviet opamp is awesome :P

I used the TL072 and a basic n transistor. Most metals were half diameter of coil, aluminium is a little more than diameter.

Not sure why your results are so low.

Mine were that low when i used a coil of 200uh. Made a new coil that is a little over 400 and it doubles my results.

[porkluvr]

Chemelec, if your connection is too slow for streaming Youtubes, you might try YoutubedownloaderHD . Point it to a Youtube url, and it will download and convert video to either AVI or MP4 that you can watch at your leisure.

It works very well but one thing that is kind of annoying is that it frequently wants to be replaced with a newer version - it will no longer download video, but with no instruction to the user.

[ODM]

It works very well but one thing that is kind of annoying is that it frequently wants to be replaced with a newer version - it will no longer download video, but with no instruction to the user.

www.onlinevideoconverter.com has been around for a couple years and doesn't install stuff on your drive. Just put on adblock while using the site

[Watanabe]

This is a great design!!!!
Someone have a link to PI of 8 Inches works ???
Someone build PCB??
I be of eyes in this project.
Very interesting for me.
Thanks
;-)


Greetings from Brazil!!!!
(sorry for my bad english)

[Watanabe]

Links not complete.

Have a mistake in PCB between IC2( pin7, pin8 ), C7, R15, Q2.
Links not complete.


Thanks.
...

[Watanabe]

I make some little modifications.
LS1 and pad (next in buzzer) are for earphone links.


Please, check.
Thanks.
;-)

[6666]

A couple of things
Mod#1
you only need R1 10K to drive T1.

Mod#2
if you replace the transistor with a fet IE: IRF740
you have to remove R5 and make R6 about 220 ohms
this puts almost the full battery voltage on the gate.

[ODM]

Would be interesting to see this one done on a quad popcorn opamp like the 324 - splitting the preamp between two stages to deal with the lower GBW, and using the one leftover opamp to make a relaxation osc for driving the tx switcher.