starting my baracuda build

[digga]

okay i brouht a new lcr meter and checked a few things
std minelab 11" mono commander coil is 1.9 ohms @ 305 uh
coiltek oval 250mm mono coil is 2.o ohms @ 305 uh
the std commander coil lowers the heat on the fet but very suspect range of deepth that said the coilteck ant that good ether
so ive brought some diffrent types of wire to wind my own
and ive searched this site over and over and there seems to be a wide range of specs
the std barra is 453uh @ 1.4 ohms
a lot of people are saying to go under the 400 uh mark
so im thinking of a spiral type first i brought 40 meters of figure 8 awg 26 wire so ive read about thirty-one turns around a dvd tube this seems like a good start
and some more .5 26 awg enameled wire ive read 27 turns for a 10/11 inch coil
and some ,5mm 26 awg multi strand same thing 27 turns for 10/11 inch what do yous all think am i way off . Or on the rite track
and what numbers would yous aim for
thanx travis
ps ive tried the coil calc and it just wont work for me any hints on what i am doing rong
thanx

[digga]

sorry ohms on both coils is 1.5 not 2 ohms

[6666]

ps ive tried the coil calc and it just wont work for me any hints on what i am doing wrong

You input the radius of the coil in MM, the wire size, the number of turns
works for me


.5 26 awg enameled wire 27 turns for a 10 inch coil gives me 562uH

[digga]

You input the radius of the coil in MM, the wire size, the number of turns
works for me


.5 26 awg enameled wire 27 turns for a 10 inch coil gives me 562uH

yer 6666 i cant get that far it goes to my download file then thats it even tried a google sercch on the link
so 6666 what do you recomend as a start what should i be aiming for as far as uh and ohms go

[sinclairuser]

with a 330ohm stock damping resistor you really need to be +400uh, thats where the heat is coming from.
you are right about people recommending lower inductances, but that is really for surf pi, in order to run lower inductance coils you need to do the damping tuneup with a scope, for those new to this or those with basic equipment its easier to hit the alexismex coil specs and run at 330 ohms damping.
its the quickest and safest way get up and running.
once you have a working detector on your homemade lashup coil, ditch it and run the coil damping tuneup with a scope, if the commercial coils need different values, just fit these in the coil plug, those commercial coils will probably run better than homemade stuff (at least to start with), you can waste a lot of materials till you get good repeatable coils.
so my advice to you is, wind a ruff and ready coil at project specs, setup detector and get it running right, then tune it to run on your commercial coils.
p.s. coil data 453uh, 1.5ohms r1 330ohms.

[digga]

thanx mate this is a big help

[sinclairuser]

how did you get on?, having reread the thread you should only need one damping resistor, the specs of your commercial coils are close enough to each other that if you say tune to the coiltek and fit the damping resistor at r1 permanently, the other coil will work fine, dont get confused and think you need to fit the damping resistor in the plug thats only done if a different value is needed.

[diego]

In case you want/need to go with a coil other than specified... how do you tune it with an oscilloscope to know what damping value to use? What IC/pin and what to look for?

[digga]

okay its been a while but i finally got around to winding a new coil i bought a 10 inch ufo style cover and wound a coil to suit i ended up with 435 uh and changed the multi turn pots for single pcb pots i still need to shield it
but the fet runs cool and after a tune up i am very happy with deapth australian 20c peice at a little over 27cm and quite noticable tone and you can just here it at 29cm just
now my next question is sheilding im thinking scotch 24 tape
do i really need sheilding i plan to only use it on the beach
thanx travis

[6666]

What does a 10 inch ufo style cover look like ?

[digga]

hi 6666 sorry for the long delay but i cant seem to upload a photo its a white one i got it of ebay for 20 dollars i will try to get
a photo for you

[digga]

this is it nice an lite to

[6666]

Thanks Digga.

[jladre]

Good day to all... i just want to ask the specific of 7660 because there are so many in the store like icl7600A, ICL7660SCPAZ, and more..

[Koala]

Good day to all... i just want to ask the specific of 7660 because there are so many in the store like icl7600A, ICL7660SCPAZ, and more..

Main difference is the supply voltage a lot have a max supply of 12V get one that has 15V

Don't trust the specs on ebay most are just a copy and paste from somewhere else. Check the specs on RS or Farnell type website

Not sure where you are based. If you can use a main distributor rather than ebay as you are more likley to get the spec you ordered.

Most ebay shops will be fine but some will be selling out of spec components.