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Thats a really good effort and result Im impressed.
You nearly got your objective sorted, Steve
You nearly got your objective sorted, Steve
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Thanks Gulfnut..
Just filled in 50-60% of the Compound mass. But only just so the coils are covered. I want to test it outside, before its closed and before the bottom shielding is made... It will give me some knowledge about shielding, and properly an idea "did I succesed" (chattering).
Ps. If somebody else should try this some day ; Dont go after the perfect Null... Ist impossible at all frequency.
Finding the best Null at 11.4 khz and 17.3 khz at the same time, is Very difficult. Mine is now 12-15 mv at both Freq.
Henrik.Comment
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Quote:"First problem... the TX must be spot on with the Inductance and the resonance. I had to take of 2 turns (now 197 - 0.315 wire).
The meter was at 19.45mH (goal 10.4) but the resonance was 150-200 Hz too low"
This is why I suggested winding a small number of extra isolated turns, like 199+2+2. Then you don't have to remove / add turns, because they are already there, just wire them up as needed., like 197 = 199-2, or 203 = 199+2+2, etc.
Quote:"Don't go after the perfect null... It's impossible at all frequencies"
It's not impossible, but it's a more advanced technique, which maybe you could try later, but for now, a 1 or 2 frequency null is good enough.
It is looking good so far.
One idea for next time, if you keep one wire of the TX connection to the co-ax cable looped up in the air, so it is clear of the resin, then you could cut it and add a small nulling loop if needed, for example if the resin affects the null as it cures. I will try and add a pic to explain, later.
Does your resin have graphite powder in it, or are you waiting for that to arrive.? If you use conductive resin, you have the problem of keeping it away from any of your un-insulated wires, like at the end of the co-ax cable.Comment
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Thanks Skippy....Yes I learned that Very small changes Winding the coils, matter a hole lot. You nailed it again, but Lucky me I could take off 2 turns and safe my work.
Good idea to keep up the TX wires.. That would I do the next time.
The graphite is still the Contact 33 Graphite.. Its a new supply I got to day. The drain wires made like you said ( S sharpe ). This idea from you did it so easy to make the graphite lay and keep 1-2 Kohm... The outside lay got connection from 4 x small holes with drainwires and the outside hold 1.5-2.0 Kohm..
This graphite powder I ordred isn't arrived. First I must learn how to use it (mix with what?) That will Be another time and another coil project.
Henrik.Comment
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I agree, trying to find out how much graphite to add to resin is difficult. I have been looking at this myself, I saw it mentioned that up to 10% by weight was possible (eg. 10 grams graphite, 90 grams resin), but you likely need less than this to get useful shielding, maybe 1 to 5 grams per 100 grams? I understand one problem with mixing graphite into resin is that it doesn't mix evenly, it settles together in corners, settles in the bottom, things like that, so it's resistance will vary a lot.Comment
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Just what I had in mind... And to make one or two coils, with a good drain wire, ist not so exspensive with the standard graphite paint.Comment
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You will see the null alter as soon as the resin goes in - I readjust as necassary during the cure.
Hope the second drain goes well - so you have one above and one below your coilComment
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Here is where I saw the figure for mixing graphite into resin:
http://www.easycomposites.co.uk/prod...-friction.aspx
Quote:"Graphite powder can be added to most resin systems (including epoxy and polyurethane) up to a maximum percentage of approximately 10% by weight. Doing so will create a very dark, shiny grey colour"Comment
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Some good information Skippy.
This is said out of the blue, but If and when I would try something graphite powder mixture... It will Be with some White paint Very thin, like those spray paint in cans... A mix with Black and White colors, could do some help to see thickness and mixture ! Just an idea.Comment
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Hi Henrikras, Another post from me that is probably just showing my ignorance but when you said, "it is too difficult to glue and hold the coils," I was reminded that I use hot melt glue gun glue to hold things temporarily in place whilst the proper stuff sets whatever that might be. Will you make a smaller coil for the Blisstool as your next project -one that we can copy, or would it be too difficult a project for people like me that know very little.Comment
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Hi Muddy... Nice to hear from you. The Glue issue was Very difficult - The smallest vibration, either the TX or the RX will move and then the coil go off balance. Thats why I gave this idea up. But nevermind now.. Soon this searchcoil no.2 is ready, and then I hope to start the work to make the 7" Bliss coil. I think many allready made tools can Be used again, and it will (I hope) not Be so difficult.
ps. I hope some kind of instruction book can Be made, so you and others with some skills can make your own coil... I'm here to help you If its possible. (I think we are at same level - learning by doing help us both a lot)
Henrik.Comment
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i would not advise you mix any paint with the graphite, i've tested both the clear lacquer and graphite, and black paint with graphite.
the black paint was identical to the clear plasticote acryllic lacquer, except it was black, but it failed even sanding it back and applying more didn't work, my guess is the pigment coats the graphite and stops it settling, which is what we want so it makes a good contact.
just a bit of advice from my experiments to save you wasting a coil.Comment
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Hi again Henrik. I shouldn't really be posting on this thread as I am only interested in what you are doing but don't really have any knowledge on the subject. I was looking at a web site called www.epemag3.com at the construction of the EPE Bounty Treasure Hunter Metal Detector. It is an extremely simplified version of what you are doing. One good tip that they mentioned was that before you pour in the resin/graphite mix, to leave a small section (40mm) of one of the coils at its centre covered with "bluetack". It should form "vertical walls" to prevent the resin going over the coil wires at that point. After the resin has thoroughly set 24 hours later you can remove the blue tack and then you have a little coil section where you can do some final bending.Comment
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LATEST NEWs about the Deus 7" coil...
Oh my god - why shall it Be SO difficult!
Situation - Its working perfect in lab, but outside the soil / ground is Breaking up the signals, just like deep and weak targets at the Stock coil, but with my homemade coil allso bigger object close to the coil, they or not clear.. Like there is interference from the ground, or like the ground is making iron signals mixed with goodies I had dig down.
air test outside - perfect. All the disc. \ ID's are same like the Stock coil, allso perfect.
This utube is made before the bottom shielding - but it tells Very Well the problem. Listen to the silver coin - like iron arround it.
link. http://www.youtube.com/watch?v=YUOK1MVXM6k&sns=em
1. I can't get into my mind, that I got a phase problem - Its working in lab. - !
2. Its must Be shielding problems and EMI / ground interference problem - !
3. Could it Be that the Graphite I use, is the wrong type ?? - Or I did something wrong doing the shielding ?
4. Could it Be that my 1.5 Kohm is to high... Even the Stock coil was measured 1.5 Kohm. ? (Graphite type, drain wire - different )
5. Could it that I made a mistake, when I found out the Shielding drain wire was connected to the RX cold side at the Stock coil,
and some how XP did it different, just dont know how.
Hope you got some VERY good ideas... I'm in trouble.
Henrik.Comment
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