[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
2
News:
Pages:  1 2 3 4 5 6   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 golddustcarl
Silver Member
*

Mood:Happy
Happy

Join Date: May, 2014
Thank you159

Activity
0%
Male
United States
Posts: 1333
Referrals: 0

7377.00 Gold
View Inventory
Windows 7/Server 2008 R2
Windows 7/Server 2008 R2
Mozilla compatible
Mozilla compatible

Awards

NOKTA SIMPLEX+,Tesoro Vaquero, VibraProbe 580, Garrett Carrot, Garrett Master Hunter ADSIII
« Reply #30 on: April 19, 2015, 08:28:00 pm »
Go Up Go Down

Quote:Posted by MCS-51
Hi again,
I think that the supply voltage, coil and power supply circuitry can be dimensioned to begin with as you say.

First some basics in short:
The maximum current that can be drawn through the coil is mainly dependant on two things, the voltage that is applied to the coil and the winding's resistance.
The coil's resistance depends on the wire's resistivity, the total length of the wire in the coil and the wire thickness.
The magnetic field occuring is mainly dependant on the current through the coil and the number of turns, the physical size of the coil has also influence.
When applying voltage to a coil, the current will rise linearily with time until the maximum current (=voltage/resistance) is reached.
The time to reach the maximum current depends on the inductance of the coil, in turn depending on the number of turns and the coil's "form factor" (thickness/dia).

Thus, it is no point keeping the pulse length longer than this time, all excess power will be waisted and the impulse will also be weakened.

The influence on an object to be found is depending on a lot of stuff, but mainly the distance to the coil and the angle to the coil's center line, simply put.
This influence gives reason to a field emitted from the object when the exciting field disappears.
This emitted field can be picked up by the same coil, or better another coil placed a little offset from the transmitting coil.
The waweform and amplitude of this signal tells much about the material, size and other things on the object, and also the distance/angle to it.

Then, the power supply must be able to cope with this special case of load (short pulse, high current), but the mean (over time) power to the coil depends on the pulse length in relation to the pulse repetition rate.
All other supply currents must of course be added to this to find the power supplie's requirements.
The battery voltage must be selected depending on all previous parameters, or be set to a value and used as parameters in the earlier calculations (which I would do).
Also, as you may see, higher voltage gives possibility to a high coil current ,which not necessarily is a great advantage in overall performance.

It is ,as you might see, important to break down the design in small blocks that can be handled.


Hopefully this will help you and others, I can assist some in the calculations but my time is limited right now because of a rough load at work.

If I missed or mixed something up, I can only refer to my age combined with little time to spend. Wise



Best wishes!



Well you said it very well. I would like to add a little more info hopefully without insulting your intelligence. A couple of other things also affect the coil current. One is the on resistance of the switch used to turn the coil on and off. The second would be resistance of connecting cables and inductance associated with them. We are not talking about a lot of resistance or inductance here, but it all adds up. In this case it reduces current or affects coil saturation times, which is also affected by cable capacitance, Ciss & Coss of mosfet driver, and coil inter winding capacitance. Too much to think about. Your estimate of total current draw of the most popular PI's is spot on. There are ways to reduce current draw especially in µcontroller models. I won't discuss them here. Thanks for you post.

Dusty Carl


Dusty Carl

Linkback:

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

http://www.thunting.com/smf/index.php/topic,60153.msg295432.html#msg295432


A bad day at gold prospecting or metal detecting is better than a good day at work.


Logged

GOLDDUST CARL

Offline MCS-51
Foil
*

Join Date: Apr, 2015
Thank you2

Activity
0%

Sweden
Posts: 3
Referrals: 0

15.00 Gold
View Inventory
Windows 7/Server 2008 R2
Windows 7/Server 2008 R2
Firefox 37.0
Firefox 37.0

Awards

no
« Reply #31 on: April 19, 2015, 11:35:54 pm »
Go Up Go Down

Dusty Carl, you're so right. Everything adds up to the total experience, and many things influence each other also.
That was the reason I did slice the basic explanation down to the very component (coil).

I will certainly not take offense from a comment like yours, no worries.  Smiley

Actually, you started a very important discussion on the circuit stability. I mentioned the dimensioning of the power supply, that is essential when it comes to overall stability and performance. A sloppy design here can ruin the functionality of the most excellent detector available, and so may the cabling and wiring do.

I think that this can be a very interesting subject to involve in.
I gladly share any useable experience from 15 years of electronic design.


Best wishes!


Linkback:

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

http://www.thunting.com/smf/index.php/topic,60153.msg295442.html#msg295442




Logged
Offline golddustcarl
Silver Member
*

Mood:Happy
Happy

Join Date: May, 2014
Thank you159

Activity
0%
Male
United States
Posts: 1333
Referrals: 0

7377.00 Gold
View Inventory
Linux
Linux
Chrome 28.0.1500.94
Chrome 28.0.1500.94

Awards

NOKTA SIMPLEX+,Tesoro Vaquero, VibraProbe 580, Garrett Carrot, Garrett Master Hunter ADSIII
« Reply #32 on: April 20, 2015, 12:38:28 am »
Go Up Go Down

You are most right. If you will notice this site has many members all with varying degrees in electronic experience. I find myself sometimes spouting out too much info for a beginner or not enough for a 40 years engineer. I just kinda have to learn to gauge it by the level of the poster. Some very knowledgeable and friendly people here who will be glad to help you figure something out, but they will not lead you by the hand. How will one learn if he doesn't do it himself?
I think we have a board where we can discuss ideas like that, and all levels of people are welcome to read and post, not just techies. I would enjoy an exchange of information and ideas.

Dusty Carl

Linkback:

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

http://www.thunting.com/smf/index.php/topic,60153.msg295447.html#msg295447


A bad day at gold prospecting or metal detecting is better than a good day at work.


Logged

GOLDDUST CARL

Offline xavier
Platin Member
*

From a rainy Brussels
Join Date: May, 2009
Thank you166

Activity
0%
Male
Belgium
Posts: 7339
Referrals: 0

32206.00 Gold
View Inventory
Windows 7/Server 2008 R2
Windows 7/Server 2008 R2
Chrome 42.0.2311.90
Chrome 42.0.2311.90

Awards
« Reply #33 on: April 20, 2015, 07:34:13 am »
Go Up Go Down

One needs to remember that the decay time of the coil is crucial to the size of the object that can be detected, If you can have a large pulse ie a lot of current yet not too much for reasons already discussed and a very fast decay time your chances of detecting small objects increase. Lets not forget that the pulse rate will also increase the chance in detecting small object, like stated before, there are so many parameters that one could spend months just designing the coil for a design. (having taken other parameters into account first)

Posted on: April 20, 2015, 02:31:39 pm
I just wanted to add a welcome to thunting.com to MCS-51 and thanks for your input.

Linkback:

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

http://www.thunting.com/smf/index.php/topic,60153.msg295457.html#msg295457


Xavier


Logged

So many questions so little time

Offline 6666
Bronze Member
*

Join Date: Mar, 2010
Thank you23

Activity
0%
Male
Australia
Posts: 200
Referrals: 0

1060.00 Gold
View Inventory
Windows 7/Server 2008 R2
Windows 7/Server 2008 R2
Firefox 37.0
Firefox 37.0

Awards

DIY, Whites 6000d, whites 2000 PI
« Reply #34 on: April 27, 2015, 06:37:20 pm »
Go Up Go Down

Gtdavid
here is another cct for your amusement.



Linkback:

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

http://www.thunting.com/smf/index.php/topic,60153.msg295822.html#msg295822



There are 1 attachment(s) in this post which you can not view or download

Please register for viewing them.

PI-111-bara.jpg


Logged
Offline golddustcarl
Silver Member
*

Mood:Happy
Happy

Join Date: May, 2014
Thank you159

Activity
0%
Male
United States
Posts: 1333
Referrals: 0

7377.00 Gold
View Inventory
Windows 7/Server 2008 R2
Windows 7/Server 2008 R2
Mozilla compatible
Mozilla compatible

Awards

NOKTA SIMPLEX+,Tesoro Vaquero, VibraProbe 580, Garrett Carrot, Garrett Master Hunter ADSIII
« Reply #35 on: April 28, 2015, 03:52:04 pm »
Go Up Go Down

Looks nice. Is there a PIC version? Not big on Atmel. I like assembly language not interpretive.

Dusty Carl

Linkback:

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

http://www.thunting.com/smf/index.php/topic,60153.msg295883.html#msg295883


A bad day at gold prospecting or metal detecting is better than a good day at work.


Logged

GOLDDUST CARL

Offline gtdavidTopic starter
Pull Tab
*

Join Date: Jan, 2015
Thank you4

Activity
0%

Australia
Posts: 20
Referrals: 0

120.00 Gold
View Inventory
Linux (Ubuntu)
Linux (Ubuntu)
Firefox 31.0
Firefox 31.0

Awards
« Reply #36 on: April 29, 2015, 06:11:44 am »
Go Up Go Down

Where is that from 6666 could you post a higher resolution pic?

As far as for my project.. Well things are getting there.
I have been working on getting the us user adjustable timing sorted out and have all but finished it.
I have changed the main detection gui as drawing lines on the screen was a bit resource hungry and just having a score displayed is proving to be more efficient.
So far I can detect a metal object at about 1-2 inches with a very basic circuit. Does not even have the op-amp as yet.
I have also been implementing a ferrous / non-ferrous indicator but it is still very problematic.
At the moment my main focus is currently on building a power supply for the unit.



Linkback:

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

http://www.thunting.com/smf/index.php/topic,60153.msg295903.html#msg295903




Logged
Offline 6666
Bronze Member
*

Join Date: Mar, 2010
Thank you23

Activity
0%
Male
Australia
Posts: 200
Referrals: 0

1060.00 Gold
View Inventory
Windows 7/Server 2008 R2
Windows 7/Server 2008 R2
Firefox 37.0
Firefox 37.0

Awards

DIY, Whites 6000d, whites 2000 PI
« Reply #37 on: April 29, 2015, 08:56:27 am »
Go Up Go Down

That file is as far as that project got, no software was published.

Linkback:

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

http://www.thunting.com/smf/index.php/topic,60153.msg295904.html#msg295904




Logged
Offline 6666
Bronze Member
*

Join Date: Mar, 2010
Thank you23

Activity
0%
Male
Australia
Posts: 200
Referrals: 0

1060.00 Gold
View Inventory
Windows 7/Server 2008 R2
Windows 7/Server 2008 R2
Firefox 37.0
Firefox 37.0

Awards

DIY, Whites 6000d, whites 2000 PI
« Reply #38 on: April 29, 2015, 07:03:57 pm »
Go Up Go Down

And then you have this one, take note this is supposed to be the correct cct.

Linkback:

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

http://www.thunting.com/smf/index.php/topic,60153.msg295925.html#msg295925



There are 1 attachment(s) in this post which you can not view or download

Please register for viewing them.

corrected-BRN%20Pi-1-M.jpg


« Last Edit: April 29, 2015, 07:05:20 pm by 6666 »
Logged
Offline golddustcarl
Silver Member
*

Mood:Happy
Happy

Join Date: May, 2014
Thank you159

Activity
0%
Male
United States
Posts: 1333
Referrals: 0

7377.00 Gold
View Inventory
Linux
Linux
Chrome 28.0.1500.94
Chrome 28.0.1500.94

Awards

NOKTA SIMPLEX+,Tesoro Vaquero, VibraProbe 580, Garrett Carrot, Garrett Master Hunter ADSIII
« Reply #39 on: April 29, 2015, 07:26:41 pm »
Go Up Go Down

Doesn't look there is a power switch. Just an oversight?
Dusty Carl


Linkback:

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

http://www.thunting.com/smf/index.php/topic,60153.msg295927.html#msg295927


A bad day at gold prospecting or metal detecting is better than a good day at work.


Logged

GOLDDUST CARL

Print
Pages:  1 2 3 4 5 6   Go Up
Jump to:  

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