my coil shell is only 5mm thick so i had to put windings side by side and i super glued them in place....but ive taken an inductance reading and it is 140uH which i guess is far too low...can i still use this coil for beach detecting for rings and coins ??? the wire is 24 awg 19 strand litz....whats the best way to drive this coil ????
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HOME MADE PULSE COIL PROBLEM
- Thread starter daverave
- Start date
icurabeachguy
New member
if you don't get any response, I'd check out the geotech forums for coil info...lots more folks on there that build their machines/coils and know quite a bit. happy hunting!
You might be able to use the coil and have it work ok if it doesn't ring. If that happens, you might be able to add more damping across the coil winding if it isn't sealed or add more damping inside the control box. In other words, the coil may not be damped enough. Simply try it and see.
Once the coil is damped properly, you should be able to use the coil but expect that coil to have less sensitivity. 140 uh is quite low inductance wise.
What detector are planning on using this coil on?
Most of the kits made are very forgiving and can use a very wide range of inductance and work.
Reg
Once the coil is damped properly, you should be able to use the coil but expect that coil to have less sensitivity. 140 uh is quite low inductance wise.
What detector are planning on using this coil on?
Most of the kits made are very forgiving and can use a very wide range of inductance and work.
Reg
i was going to use the coil with a hammerhead pi circuit....if i were to use more tx current would it help to overcome the sensitivity problem ??? or maybe wind a small coil in the centre of coil and place in series with the main coil which i guess would increase the inductance ??? 
The HH detector doesn't lend itself to easily increasing the coil current. You could add more inductance in series with the existing windings if that is possible, but personally, I would simply try it the way it is first and see what happens. Also, the coil would let you shorten the delay some which would help with smaller gold objects.
Reg
Reg
I own and use a Crossbow Pulse machine that is based on the Hammer head platform it was made by George who co owns the Geotech forum,the 10'' coil was of course matched and it does work very well indeed,since i have own it i have added additional coil but rather than have the frustration of winding and tuning them myself i was able to buy brand new Garrett Seahunter coils from the biggest dealer in Birmingham,it does not take much working out who i am on about.But these coils work superbly well as that was done was change the coil plugs over and i think George added a damper resistor inside the control box for me.
Curently use both the 8'' and 14''x10 Garrett Mono coil,also have been working on a 18x12 coil using a Coiltek coilcase that i was able to buy brand new but although i have had it working not sealed it as yet,but i also had a 5'' coil made by a forum member that was shipped over from Canada,it does work well with the Hammerhead setup but you do need to adjust the delay just right to get it to work exactly right.
As building coils can be a hit and miss thing when building a PI machine this is the reason i went down the route of getting a ready built coil from a main brand name and i i feel this eliminates the headache of building a coil and setting it all up,and the Garrett Seahunter coils are ultra cheap to buy brand new as well.
Good luck and hope it all comes together for you.
Curently use both the 8'' and 14''x10 Garrett Mono coil,also have been working on a 18x12 coil using a Coiltek coilcase that i was able to buy brand new but although i have had it working not sealed it as yet,but i also had a 5'' coil made by a forum member that was shipped over from Canada,it does work well with the Hammerhead setup but you do need to adjust the delay just right to get it to work exactly right.
As building coils can be a hit and miss thing when building a PI machine this is the reason i went down the route of getting a ready built coil from a main brand name and i i feel this eliminates the headache of building a coil and setting it all up,and the Garrett Seahunter coils are ultra cheap to buy brand new as well.
Good luck and hope it all comes together for you.
i think if you make your own coils then you can make them lighter in weight as many of the commercial coils are very heavy cause of the amount of resin used...i do try and pack the coils out with balsa wood and plastic pieces so not so much resin used and lighter coil....plus its fun making your own coil and seeing what you can find on the beach with it.
Most home made PI's are based upon Eric Fosters designs and as such are very forgiving. In other words, they will work with a wide range of inductance, but may require more or less damping for best results.
A standard (if there is a standard) inductance is about 300 uh. Increasing the inductance above the 300uh will almost always be stable but may not work at the minimum delay. This is not a problem when coin hunting since about any delay above 15 usec usually will work. Using a delay of 30 to 50 usec eliminates most ground signals and a lot of trash responses such as signals from most foil while still detecting US coins.
Building a home made PI for nugget hunting is extremely difficult since none of the regular kits have any form of ground balance. The GS 4 doesn't have a pc board readily available but is a good design for nugget hunting. This GS 4 could be simplified making it easier to build but I don't have time to do that at this time.
For those of you needing a coil form, there are some for sale on Ebay and sold by Bill Hays. Bill only takes checks now, though.
Reg
A standard (if there is a standard) inductance is about 300 uh. Increasing the inductance above the 300uh will almost always be stable but may not work at the minimum delay. This is not a problem when coin hunting since about any delay above 15 usec usually will work. Using a delay of 30 to 50 usec eliminates most ground signals and a lot of trash responses such as signals from most foil while still detecting US coins.
Building a home made PI for nugget hunting is extremely difficult since none of the regular kits have any form of ground balance. The GS 4 doesn't have a pc board readily available but is a good design for nugget hunting. This GS 4 could be simplified making it easier to build but I don't have time to do that at this time.
For those of you needing a coil form, there are some for sale on Ebay and sold by Bill Hays. Bill only takes checks now, though.
Reg
As for making coils lighter, there is a light weight resin made by Smooth-On that is quite light. The name of this resin is Featherlite. Add microspheres to the resin and it becomes even lighter.
I also have used two part foam in the rigid type and filled one half of a coil form and cut it flush. I then route out the space for the windings and seat the windings with the featherlite resin. This makes a light coil that is quite rigid.
Reg
I also have used two part foam in the rigid type and filled one half of a coil form and cut it flush. I then route out the space for the windings and seat the windings with the featherlite resin. This makes a light coil that is quite rigid.
Reg
the two detectors ive already made work at about 25uS delay and are ok for most coins but not very good on US nickles and larger gold rings which has always dissapointed me...thats why i wanted to make a coil running at about 10uS delay to give me better depth on these lower conductive items....using the hammerhead so i can adjust each parameter and hopefully make a de tector that will improve on my other two detectors for sensitivity on low conductive items...the featherlight resin im not sure if its availiable in the UK but i will take a look on ebay !!! last time i p otted a coil i spilt black resin over the carpet as i live in a flat with no garden workshop
