Jump to content
Nugget Shooter Forums
Sign in to follow this  
homefire

Twisting Up DIY Coils ?

Recommended Posts

OK, Back at it.  Got side tracked on a few things.  

Decided to go ahead and try the .2mm (32AWG) wire after reading on the Geotec Forum someone used it with reasonable results.  

DC Resistance goes up but it seems with little consequences.  Here are some basic numbers but sense I'm going with a 1" or so smaller form I will need a few more wraps or turns of wire to meet the uH numbers.  

The As Build :

Diameter: 255mm x 137 mm (one coil)
Wire size: .25mm (30 AWG) enameled
Tx inductance: 6.0mH
Tx resistance: 18 – 25 Ohms
Tx resonance - About 14.5 kHz
Rx Inductance: 6.5mH
Rx resistance 18 – 25 Ohms
Rx resonance with 15nF – About 16.1 kHz
 
     
Attempted Build:

Tx
30 (AWG)      Wire Resistance:  24.378 ohms
Gauge   32 (AWG) 236.22ft  Wire Resistance:  38.764 ohms

Rx
30 (AWG) 216.53ft Wire Resistance:  22.346 ohms ohms
32 (AWG) 240ft = 39 ohm

My set up and Deviations marked in red on coil plan.
===

 

1211171130.jpg

1211171129.jpg

1211171128.jpg

Wire Requirement.PNG

  • Like 1

Share this post


Link to post
Share on other sites

Coil came out to 5.5mH prior to lashing and was able to get it spot on 6.5 by lashing it.  It will change some with added pressures from spiral wrap I'm sure.  I hit it with some krylon paint as adhesive to try and keep it from moving much.  


I wrapped coil with the Teflon and things did change a bit but not as expected.  The uH went down.  LOL  Now getting like 6.367.  I'll play at wrapping some more Teflon tighter and see if I can get it back up. I'm good with that.  I can make up the difference on Tx  if needed and still be  will in the 14Khz Tx. 

1211171541Laced.jpg

1211171655AfterTeflon.jpg

1211171658 Fit.jpg

  • Like 1

Share this post


Link to post
Share on other sites

 Ok, Getting there !  I got the issues corrected.

Tx

Gauge   32 (AWG) 214ft  Wire Resistance:  38.764 ohms
107 turns
6.05 mH

Rx

32 (AWG) 224ft = 39 ohm
113 Turns
6.507mH

Going to fit in the Housing Nice.  Now I need to tac glue it to a peace of card board and tune Null it.  

 

1212171627 FITTING.jpg

  • Like 2

Share this post


Link to post
Share on other sites

Very fascinating Homey. Do the coil windings just get glued down to the coil housing, or just to the cardboard you mentioned and a layer of foam over it to keep it from moving inside the housing?

It'll be great when you take it out and find something with it. :D

Share this post


Link to post
Share on other sites

Dave I will just tac glue them to some card board to get them Nulled.  That requires moving one or both coils to the point that the Rx Coil is cancelling out the Transmitted signal.  At this point the Receive signal will be based on mostly the Target Signal only. 

Later I will glue the card board on some foam as filler/spacer.   Later I'll blow expanding foam in the housing securing all.   In this case the Shielding is going to be a Conductive Carbon based paint within the coil housing. 

This one is for the guy I'm building the TGSL detector for. 

All Documents required can be downloaded from Geotech if anyone is interested.  Files are to large to post here.    http://www.geotech1.com/forums/showthread.php?15710-TGSL-Complete-Details

Dave, I'm still working on the Engine Management.  Just getting this one out of the way. 

 

TxRx PhaseRelation.PNG

  • Like 3

Share this post


Link to post
Share on other sites

Ahh...I see! So the initial tacking down is just for tuning the coils. How much leeway is there in the coils position to each other? If you bump one and move it a couple thousandths during assembly...will it screw up your tuning?

Share this post


Link to post
Share on other sites

Piles of stuff can come to play.   You want the two coils as symmetrical to each other as possible.  Shift one or the other laterally can throw you out.   Just a mm or so can mean in or out of what your looking for.    When you get done it's best to have any output on the Rx Positive of the Null on this detector.

  • Like 1

Share this post


Link to post
Share on other sites

Not so sure this .2mm wire is going to work as advertised.  Having issues getting it to sing on the Tx Oscillator. 

Share this post


Link to post
Share on other sites

 That blows. How long did it take to wrap and tie those coils?

 

Share this post


Link to post
Share on other sites

LOL, only a couple of hours.  Not done fuddling with it yet.  Think I can just change the Bias on the Transistor and get it to do it's thing.   It starts some times and not others. 

I used the new Printer to print a few (10) pages of that program I'm working on.  Have  one section all marked up as to what changes I need .  Going to make those changes and give it a go.  I need to bread board the Display to the MEGA2560 and see if it will run.  Wish I knew what I was doing a whole lot better ! :brows:

  • Like 1

Share this post


Link to post
Share on other sites

Glad you might be able to salvage those coils still. 

It seems building my engine is the easy part...I think you have the hardest job. 

It's been a learning experience for sure:)

Edited by ArcticDave
  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×