Baracuda pi coil problem

[grizzly]

I have a Baracuda kit from Silverdog. I put it together just by reading the PCB and placing the components. It seems to work but I cant seem to find a good design for a coil. I got some 24g stranded wire with the plastic shield. I wound the whole 100 feet around a 2 inch circle and ended up with about 9.5 inches O.D. and 63 turns. I know this is too many turns but I dont know how many I need? I have tried the Coil calculator on the coils forum and it always gives me numbers like .904 mh. Other calculators give me 478mh or 365mh. This is with 35 turns 9.5 inch O.D. and about a 6 inch I.D. I am totaly new to this and am wondering if I could get some direction on setting up the detector and the right number of turns to get around the suggested 450mh-500mh. Also there are three Pots on the PCB one says Thresh one pulse delay and the other is blank? Which one do I put the finger adjustable pot on? Should I get finger adjust pots for the others? I have other questions but this is a start. Thanks

[Qiaozhi]

I have a Baracuda kit from Silverdog. I put it together just by reading the PCB and placing the components. It seems to work but I cant seem to find a good design for a coil. I got some 24g stranded wire with the plastic shield. I wound the whole 100 feet around a 2 inch circle and ended up with about 9.5 inches O.D. and 63 turns. I know this is too many turns but I dont know how many I need? I have tried the Coil calculator on the coils forum and it always gives me numbers like .904 mh. Other calculators give me 478mh or 365mh. This is with 35 turns 9.5 inch O.D. and about a 6 inch I.D. I am totaly new to this and am wondering if I could get some direction on setting up the detector and the right number of turns to get around the suggested 450mh-500mh. Also there are three Pots on the PCB one says Thresh one pulse delay and the other is blank? Which one do I put the finger adjustable pot on? Should I get finger adjust pots for the others? I have other questions but this is a start. Thanks

OK - let's look at your calculations:
9.5" diameter = 241.3mm. Therefore the radius is 121mm.
With 63 turns, the inductance (from the Coil Calculator) is 2.585mH, which is far too high.
I assumed the wire is 0.56mm thick.
You probably entered the diameter into the calculator instead of the radius. This is clearly mentioned in the introductory notes.

If you use 25 turns on the same diameter coil, the inductance will be around 450uH.

[bernte_one]

hello grizzly
try first a simple monoloop
of 0,25 or 0,5qmm2 litz wire (ho5vk)
24 turns on 27cm diameter
schould all work with a good short delay set

regards

[silverdog]

I have a Baracuda kit from Silverdog. I put it together just by reading the PCB and placing the components. It seems to work but I cant seem to find a good design for a coil. I got some 24g stranded wire with the plastic shield. I wound the whole 100 feet around a 2 inch circle and ended up with about 9.5 inches O.D. and 63 turns. I know this is too many turns but I dont know how many I need? I have tried the Coil calculator on the coils forum and it always gives me numbers like .904 mh. Other calculators give me 478mh or 365mh. This is with 35 turns 9.5 inch O.D. and about a 6 inch I.D. I am totaly new to this and am wondering if I could get some direction on setting up the detector and the right number of turns to get around the suggested 450mh-500mh. Also there are three Pots on the PCB one says Thresh one pulse delay and the other is blank? Which one do I put the finger adjustable pot on? Should I get finger adjust pots for the others? I have other questions but this is a start. Thanks

Your finger pot should be on the thresh
the offset pot should be set to 0v on ne5534 pin 6 with coil connected
delay best set with a scope, or adjust for best detection - (these pots are 25 turn)

[grizzly]

Where can I find litz wire? And does this coil require shielding. I already have the flat coil I have been working with. I was figuring 35 turns would be correct, with the numbers I put in the calculators. Thanks for the 6 pin tip I had no idea of how to set this up. Do I test across the 6 pin to the negative battery lead?

[silverdog]

Where can I find litz wire? And does this coil require shielding. I already have the flat coil I have been working with. I was figuring 35 turns would be correct, with the numbers I put in the calculators. Thanks for the 6 pin tip I had no idea of how to set this up. Do I test across the 6 pin to the negative battery lead?

yes you do

ApBerg I believe sets the offset from LF412 pin 1

have a good read here - http://www.geotech1.com/forums/showt...aracuda&page=5

[Qiaozhi]

Where can I find litz wire? And does this coil require shielding. I already have the flat coil I have been working with. I was figuring 35 turns would be correct, with the numbers I put in the calculators. Thanks for the 6 pin tip I had no idea of how to set this up. Do I test across the 6 pin to the negative battery lead?

35 turns is still too many. Did you see my post here? ->
http://www.geotech1.com/forums/showp...70&postcount=2

[grizzly]

Tried adjusting pin 1 on LF412 No change. Adjusting pin 6 on ne5534 seems to work. I am using 35 turns now 24 cm od and 14.25 cm id. wire is 24g with pvc coating about 1mm. http://deepfriedneon.com/tesla_f_calcspiral.html This calculator gives me 337 mh.
This one http://www.66pacific.com/calculators/coil_calc.aspx gives 468mh.
The one on the sticky gives .455 mh. Im confused at how I could get such different results?

I am getting a signal through the machine. I get about 24 cm on a quarter 2.5cm x 1 mm coin. But the coil seems unstable. Makes noise when I move it.

[Qiaozhi]

Tried adjusting pin 1 on LF412 No change. Adjusting pin 6 on ne5534 seems to work. I am using 35 turns now 24 cm od and 14.25 cm id. wire is 24g with pvc coating about 1mm. http://deepfriedneon.com/tesla_f_calcspiral.html This calculator gives me 337 mh.
This one http://www.66pacific.com/calculators/coil_calc.aspx gives 468mh.
The one on the sticky gives .455 mh. Im confused at how I could get such different results?

I am getting a signal through the machine. I get about 24 cm on a quarter 2.5cm x 1 mm coin. But the coil seems unstable. Makes noise when I move it.

I almost give up!

The deeppfriedneon calculator is for spiral coils, the 66pacific calculator uses Wheeler's equation, which is intended for solenoid coils, and the sticky calculator uses the more accurate Brook's equation. 35 turns is too many. You should be using somewhere between 20 and 25 turns.

[grizzly]

Thanks. I have tried 25 turns. I am not very good at adjusting yet so I need to dial it in. I tried 35 first because its easier to remove turns than to add them back. I have noticed that when I set the machine to have best response it will give a solid tone when coin is held near center, no motion like a pinpointer.

[satdaveuk]

hello grizzly
try first a simple monoloop
of 0,25 or 0,5qmm2 litz wire (ho5vk)
24 turns on 27cm diameter
schould all work with a good short delay set

regards

Hi
Been trying to get some of your cable here in the uk, somewhere on here you put a link to where you get it, can you direct me to it again please
Hope all is well
Regards
Dave

[bernte_one]

hello dave
maybe here this shop send to uk
http://stores.ebay.de/EBK-Extertal/K...=p4634.c0.m322

regards