Help making coil for Surf pi 1.2 kit

[Boe]

Hello.

I'm trying to make a decent coil to my surf pi kit. I bought this cover on ebay that I will use as coil housing. The cover has i diameter 280 mm.
The wire I have is RK (H07V-K) 1,5mm2.
So what I wonder is how many turns I need with wire and if this may be a good coil.

[Qiaozhi]

Hello.

I'm trying to make a decent coil to my surf pi kit. I bought this cover on ebay that I will use as coil housing. The cover has i diameter 280 mm.
The wire I have is RK (H07V-K) 1,5mm2.
So what I wonder is how many turns I need with wire and if this may be a good coil.

You can use this coil calculator to determine the number of turns -> Coil Calculator

[kt315]

uff... this wire you use is fat for your housing. take 0,6-0,8 mm diameter wire. this fat wire will be good for big coil, 1 meter x 1 meter. not for small coils.

[Boe]

Qiaozhi: Thanks! But what is the ideal inductance with the surf pi 1.2?





kt315: Yes, I feared that it might be too thick. I can maybe 20 turn with this wire, with four rounds in width and five layers. That gives me 0.247 mH in the coil calculator?

[kt315]

......

[Boe]

it looked like a handy program, so I downloaded it what about this? (if 350 uH is a good inductance)

[kt315]

Boe, please read INSIDE THE METAL DETECTOR on 146 page, at first.

[Qiaozhi]

Qiaozhi: Thanks! But what is the ideal inductance with the surf pi 1.2?

For a 140mm radius coil, wound with 1.5mm diameter wire, you should get the following:
20 turns = 284uH
21 turns = 312uH
22 turns = 340uH

Any of these should be OK for the Surf-PI.
The final measured value of the coil will depend on how tight you bind the wiring. If you use spiral wrap, and then cover it a layer of electrical tape, the calculated and measured values should be very close.

[DanZ]

You can use this coil calculator to determine the number of turns -> Coil Calculator

Thank you for that Coil calculator link! That sure is handy to have.

Best regards,
Dan

[Jackhammer]

Are you saying the coil wires need to be bound tightly?

For a 140mm radius coil, wound with 1.5mm diameter wire, you should get the following:
20 turns = 284uH
21 turns = 312uH
22 turns = 340uH

Any of these should be OK for the Surf-PI.
The final measured value of the coil will depend on how tight you bind the wiring. If you use spiral wrap, and then cover it a layer of electrical tape, the calculated and measured values should be very close.

[sinclairuser]

yes with thick wire like that, capacitance should not really matter as the gap will still be sufficient due to the thickness of the plastic insulator, so when tightly bound you wont get falseing when bumping rocks etc.
when i started, i wound a barracuda coil out of 2mm wire like that and it worked fine, yours is a smaller diameter, and less winds, the problem with that type of wire is it can be heavy(mine was), the type of coil shell you have is injection molded as well while they are excellent shells strong etc, they are quite heavy, it all ads up.
i would wind a rough coil out of that wire for testing and setup, but save that shell for some better wire, the degaussing loops out of old crt televisions and monitors, wind good coils and can be got for nothing, its the loop of wire that is fitted around the screen, plenty of coil wire there just take off the tape and wind a coil off the loop, you can get a few good coils that way.

Are you saying the coil wires need to be bound tightly?

[Silver Dollar]

Which coil would work better 250 uh or 350 uh? I understand it is a balance between
TX power and RX signal. I have only one housing and might want to use it on different
PI boards (Chance, HH, DP) and so want to choose the best value for it.

Would I mess it up badly by having 2 taps on the coil to allow say 350 and 450 uh?

Those CRT coils are the best! I got a free TV and took the HV transistor, a High voltage
FET, A bunch of caps and that degaussing coil. It is about 6' by 20 turns and a good size
for PI coils!

[Jackhammer]

Thank you for confirming. I have some .5mm magnet wire for my surf pi 1.2 coil. I followed the calculator and have it bound pretty tightly in just a round coil, with the wire in grouped as a round bunch, not flattened out. I was concerned i have the coil windings bound too tightly, but sounds like i should have them grouped together relatively tightly. I have a R6U coax cable and bnc connector for the project box housing pass thru. Will that work ok? Seems to be about 1.5 ohms at the connector leads i will solder the board leads to. I do not have a way to check capacitance yet. I am having difficulty getting sound out of it after completing the build, so am in the process of verifying everything is connected properly, and was concerned about my coil too. Thank you for sharing your knowledge so freely. Your support is appreciated.