[x] Welcome at THunting.com!

A fun place to talk about Metal Detecting, Treasure Hunting & Prospecting. Here you can share finds and experience with thousands of members from all over the world

Join us and Register Now - Its FREE & EASY

THunting.com
Treasure Hunting & Metal Detecting Community
   
Advanced Search
*
Welcome, Guest! Please login or register HERE - It is FREE and easy.
Only registered users can post and view images on our message boards.
Did you miss your activation email?

Login with email, password and session length
Or Login Using Social Network Account
News:
Pages:  1 2 3 4 5   Go Down
Print
Share this topic on FacebookShare this topic on Del.icio.usShare this topic on DiggShare this topic on RedditShare this topic on Twitter
Tags:
0 Members and 1 Guest are viewing this topic.
Offline Homefire
Global Moderator
Platin Member
*****

Join Date: Jan, 2009
Thank you661

Activity
0%
Male
United States
Posts: 15906
Referrals: 0

52360.00 Gold
View Inventory

Awards
« Reply #30 on: September 02, 2010, 11:12:54 am »
Go Up Go Down

How and why would you retard the TX Signal?

All you want to do is compare the two.

You just need a Arbitrary Point and take samples from there?

Is the Current Ahead of Voltage or Lagging?

It's all a funtion of 2Pfl.

I'm Confused.

Capacitance Lags current by 90 degree and Inductance ( Voltage) leeds by 90 degree.

I would think the right set up of Compartor would do the job?



Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,6514.msg113537.html#msg113537




Logged
Offline xavier
Platin Member
*

From a rainy Brussels
Join Date: May, 2009
Thank you165

Activity
0%
Male
Belgium
Posts: 7339
Referrals: 0

32206.00 Gold
View Inventory

Awards
« Reply #31 on: September 02, 2010, 03:12:42 pm »
Go Up Go Down

You think you're confused you should see my face!   I see what you are saying now with the comparator OK well back to the books will keep you posted.

Regards Xavier

Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,6514.msg113570.html#msg113570


Xavier


Logged

So many questions so little time

Offline Homefire
Global Moderator
Platin Member
*****

Join Date: Jan, 2009
Thank you661

Activity
0%
Male
United States
Posts: 15906
Referrals: 0

52360.00 Gold
View Inventory

Awards
« Reply #32 on: September 02, 2010, 03:27:51 pm »
Go Up Go Down

I know electronics but wizz I are Not.

Could you use the output from a PLL Phase Locked Loop? It could be based on the TX freq?

You could use the Correction Voltage Based the Return or Received signal to determine the phase change?

You could bias the correction voltage and use it as a type of  Ground Ballance?

Just the Ramblings of a sick Mind.

Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,6514.msg113571.html#msg113571




Logged
Offline GoldDigger1950
The Old Man and the Soil
Global Moderator
Platin Member
*****

Just call me GD.
The Old Man and the Soil
Join Date: Jun, 2009
Thank you221

Activity
0%
Male
United States
Posts: 11218
Referrals: 12

47843.00 Gold
View Inventory

Awards

Garrett Groundhog ADS, Garrett Sea Hunter, Bounty Hunter Tracker IV, Bounty Hunter Pioneer 505,Minelab Eldorado Mk II, Tesoro Compadre, Tesoro Tiger Shark & A Few Home Brew Detectors
« Reply #33 on: September 02, 2010, 04:24:39 pm »
Go Up Go Down

The return signal on metal in the ground is so weak that the TX field can mask it. You have two choices. Either you can do a RX reading while the oscillating TX signal is doing a zero crossing (that's when the voltage is at zero as it oscillates from positive to negative) or you can turn off the TX pulse for a short time. The latter is what is done most easily in homebrew designs. Doing an RX reading during this quiet time is the best way to sense the collapsing fields on the metal in the ground. That collapse starts just as soon as the TX goes silent and lasts until all of the energy in the metal is gone. It's not long. The timing between turning off the TX and starting the RX is critical. Do it too soon and the TX field will not have collapsed yet causing the RX to see a target which isn't there.

This, by the way, is the most common cause of the question, "My DIY detector makes a solid beep. What did I do wrong?"

If you turn it off too late, as may be the case with Xavier, the signal is sensed at a greatly diminished distance because the field resulting from eddy currents in the target has already diminished to a lower than optimum point. The Fo, commonly called the "F sub O," or frequency of operation has an effect on this collapse time based on three factors. The type of metal, mass of the metal and the shape. All three have different effects on the field that is there and those differences are how discrimination works. Thus, some frequencies are better for finding gold nuggets, some better for finding gold coins and some better for finding gold rings. Because shape and mass play a part, that explains why you can find a small gold ring and sometimes miss a big one. You can experiment with this if you are lucky enough to have a gold coin, nugget and various sized gold rings in your collection. Keeping a chart of each of your detectors and their response can improve your odds in the field.

Homefire, you already know about the relationship to timing in PI circuits. You once recommended a resistor change to me for my Sea Hunter which would have changed to timing relationship to one better suited to gold targets.

Xavier, a square wave is an infinite number of sine waves being switched on and off. It will have zero difference electronically.

Isn't this dry, boring theoretical stuff fun? As we continue to discuss these things, you can get a glimmering of why it is so difficult to see a newbie trying to build a metal detector from parts. It's a bit like watching a farmer try to build a tractor from iron ore. We all know it can be done but the question is, "Should the farmer really do it himself?"

Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,6514.msg113573.html#msg113573




Logged

It's all about that moment when metal that hasn't seen the light of day for generations frees itself from the soil and presents itself to me.
Let's Talk Treasure!

Offline xavier
Platin Member
*

From a rainy Brussels
Join Date: May, 2009
Thank you165

Activity
0%
Male
Belgium
Posts: 7339
Referrals: 0

32206.00 Gold
View Inventory

Awards
« Reply #34 on: September 03, 2010, 01:34:31 am »
Go Up Go Down

Hi GD

Well this one is printed too I was thinking like you mentioned in your first paragraph to switch off the TX then Homefire mentioned using a comparator and I think that I will go that rout I do not have the experience or knowledge yet to go any other way. I was thinking to use the received signal to switch of the TX but that may be too late so what I think I should do is make a signal generator and a receiver hook it all up to the PC scope then see what I can come up with.

Regards Xavier   

Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,6514.msg113622.html#msg113622


Xavier


Logged

So many questions so little time

Offline bmn
Pull Tab
*

Join Date: Jan, 2009
Thank you0

Activity
0%

United States
Posts: 6
Referrals: 0

56.00 Gold
View Inventory

Awards

Homebuilt
« Reply #35 on: September 23, 2010, 05:46:25 am »
Go Up Go Down

I want it now! But I can't download the files yet! I don't have 5 posts!

Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,6514.msg117049.html#msg117049




Logged
Offline Homefire
Global Moderator
Platin Member
*****

Join Date: Jan, 2009
Thank you661

Activity
0%
Male
United States
Posts: 15906
Referrals: 0

52360.00 Gold
View Inventory

Awards
« Reply #36 on: September 23, 2010, 09:43:05 am »
Go Up Go Down

LOL! you just made Number 6!

Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,6514.msg117078.html#msg117078




Logged
Offline xavier
Platin Member
*

From a rainy Brussels
Join Date: May, 2009
Thank you165

Activity
0%
Male
Belgium
Posts: 7339
Referrals: 0

32206.00 Gold
View Inventory

Awards
« Reply #37 on: September 23, 2010, 11:07:28 am »
Go Up Go Down

Ho I do wonder at times  Grin

Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,6514.msg117090.html#msg117090


Xavier


Logged

So many questions so little time

Offline Nc-Dirty-digger
Bronze Member
*

Join Date: Oct, 2009
Thank you5

Activity
0%

United States
Posts: 120
Referrals: 0

745.00 Gold
View Inventory

Awards

minelab xterra70/garrett1350/minelab relic hawk
« Reply #38 on: November 09, 2010, 09:19:51 am »
Go Up Go Down

i haven't been here in awhile. has someone figured this thing out?

Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,6514.msg125059.html#msg125059




Logged
Offline Homefire
Global Moderator
Platin Member
*****

Join Date: Jan, 2009
Thank you661

Activity
0%
Male
United States
Posts: 15906
Referrals: 0

52360.00 Gold
View Inventory

Awards
« Reply #39 on: November 09, 2010, 10:51:18 am »
Go Up Go Down

LOL!  You have just been bumped to Guru Status!   

Were waiting for you post.



{alt}

Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,6514.msg125064.html#msg125064
http://i371.photobucket.com/albums/oo160/berquistj/space1.gif




Logged
Print
Pages:  1 2 3 4 5   Go Up
Jump to:  

Powered by SMF 1.1.19 | SMF © 2005, Simple Machines | Sitemap
Copyright THunting.com