Updated Mirage PI (Ex Hammerhead)- Mono Coil, DD Coil or Super D Coil Options

[Elliot]

Hi, did you get the ground balance to work ?

. That's a different project I'm working on. My Aqualand project took over from it. Even in lockdown, time seems to fly.

[Elliot]

I've got one Mirage Gold-Max pcb left from the current batch if anyone's thinking of building one this side of Christmas.

[Sean_Goddard]

Just a suggestion, try Silicon carbide FETS and LAPP brand cable.

Dielectric constant for fluorocarbon fishing line is close enough to PTFE as not to matter from experiments.

I laid two 1m length of wire parallel spaced with 120lbs fluorocarbon, measured the capacitance, then removed the line and remeasured it. As I knew the dielectric constant of air, I could get a working value for the fluorocarbon. Just a suggestion you might try to verify my statement.

Godigit, for the spool, cut slots in them then when finished, pour epoxy resin to hold the coil in place. If you use foam board for the former, you can clamp the finished coil between two metal sheets and pour acetone between them to dissolve it. Quickly clamp the metal sheets tightly and leave to set. The result will be a rock solid very thin, lightweight, Ulta fast spiral coil.

[MartinB]

Just a suggestion, try Silicon carbide FETS and LAPP brand cable.

Dielectric constant for fluorocarbon fishing line is close enough to PTFE as not to matter from experiments.

I laid two 1m length of wire parallel spaced with 120lbs fluorocarbon, measured the capacitance, then removed the line and remeasured it. As I knew the dielectric constant of air, I could get a working value for the fluorocarbon. Just a suggestion you might try to verify my statement.

Godigit, for the spool, cut slots in them then when finished, pour epoxy resin to hold the coil in place. If you use foam board for the former, you can clamp the finished coil between two metal sheets and pour acetone between them to dissolve it. Quickly clamp the metal sheets tightly and leave to set. The result will be a rock solid very thin, lightweight, Ulta fast spiral coil.

Hi Sean,
Sounds interesting. Have you got any photographs?

[Coolmakina]

Thanks Green. The wealth of knowledge on this forum is inspiring! I'm trying my best to keep up. As far as i can tell from your simulations, the main difference between your plots is the damping resistor value, which clearly/significantly effects the decay time to reach 1mV by about 2-3uS (green line?) I also note that the plot with the 965 R1 value has a table top peak fly-back voltage, which is not as good for creating back-EMF in the target I would have thought. It's like cracking a whip I reckon - the sharper/faster the flick, the more "sound" you get back. Also, you have a bypass link on D1 for the plot where R1=420R (which I assume is there to simulate the circuit without the effect of D1). Also, I don't understand the V3 power supply to the cathode end of D2. I haven't seen that configuration before and am not sure what to make of it. Have you chosen the use of the SPA11N60C3 for any particular reason over an IRF840? I tried to use my cro to assess the 1mV cut-off point, but like you said, a linear scale makes it impossible (why don't cheap cros' have a log scale switch????). I really appreciate the feedback! My other big challenge is to find a schematic for a really clean +5v/-5V power supply (all tips most welcome).

Hi, forgive my lack of knowledge, first step in this electronics world.
would this type of circuit ensure clean power supply?

[Elliot]

Just a suggestion, try Silicon carbide FETS and LAPP brand cable.

Dielectric constant for fluorocarbon fishing line is close enough to PTFE as not to matter from experiments.

I laid two 1m length of wire parallel spaced with 120lbs fluorocarbon, measured the capacitance, then removed the line and remeasured it. As I knew the dielectric constant of air, I could get a working value for the fluorocarbon. Just a suggestion you might try to verify my statement.

Godigit, for the spool, cut slots in them then when finished, pour epoxy resin to hold the coil in place. If you use foam board for the former, you can clamp the finished coil between two metal sheets and pour acetone between them to dissolve it. Quickly clamp the metal sheets tightly and leave to set. The result will be a rock solid very thin, lightweight, Ulta fast spiral coil.

I've been meaning to try using fluorocarbon filament as a wire spacer. As I'm first sampling at 6uS already with my own coils, I don't think the improvement, if any, would be much on teeny gold flakes.

[Elliot]

Hi, forgive my lack of knowledge, first step in this electronics world.
would this type of circuit ensure clean power supply?

The latest Mirage Gold-Max Pi machine has a wonderfully clean power supply, FET stage and fast sampling circuit (6uS).

[green]

I've been meaning to try using fluorocarbon filament as a wire spacer. As I'm first sampling at 6uS already with my own coils, I don't think the improvement, if any, would be much on teeny gold flakes.

Has anyone compared coils with and without fluorocarbon spacer? I get very little capacitance winding a spiral coil without the spacer. Should I expect the spacer to improve the coil?

[bbsailor]

Has anyone compared coils with and without fluorocarbon spacer? I get very little capacitance winding a spiral coil without the spacer. Should I expect the spacer to improve the coil?

The dielectric constant of a vacuum is 1. Air raises to 1.00059 at sea level but can also change by the range of humidity in the air, going up with higher humidity. If the dielectric constant of your fluorocarbon spacer is 2 or higher, then removing it should represent less coil wire seen capacitance between the windings. Any materiel that is very close to the magnetic field in the coil wire will affect the coil self resonance. The rule of thumb is to use wire insulation with the lowest dielectric constant and or physically space winds with more air between the turns. Insulation thickness also affects the final coil inductance and self resonance.

My best coils use thicker 600V or higher Teflon insulation with a dielectric constant near 2. This way I can make a bundle wound coil, use PE spiral wrap, and space the shield away from the coil wire to minimize coil to shield capacitance. I used Scotch 24 as a wire mesh shield, which minimizes the coil to shield capacitance due to less area than a foil like shield. I have found through experimentation that cutting the width of the Scotch 24 just wide enough to not overlap when going around the coil bundle prevents the shield from being seen as a target at lower delays.

Bottom line, anything you can do to reduce the capacitance seen by the coil after the TX pulse turns off and the discharge slope energizes the targets and the damping resistor value is damping the oscillations enough so the RX stage can sample as early as possible. Less capacitance allows higher damping resistance values and potentially earlier sampling.

Joseph J. Rogowski

[green]

The dielectric constant of a vacuum is 1. Air raises to 1.00059 at sea level but can also change by the range of humidity in the air, going up with higher humidity. If the dielectric constant of your fluorocarbon spacer is 2 or higher, then removing it should represent less coil wire seen capacitance between the windings. Any materiel that is very close to the magnetic field in the coil wire will affect the coil self resonance. The rule of thumb is to use wire insulation with the lowest dielectric constant and or physically space winds with more air between the turns. Insulation thickness also affects the final coil inductance and self resonance.

My best coils use thicker 600V or higher Teflon insulation with a dielectric constant near 2. This way I can make a bundle wound coil, use PE spiral wrap, and space the shield away from the coil wire to minimize coil to shield capacitance. I used Scotch 24 as a wire mesh shield, which minimizes the coil to shield capacitance due to less area than a foil like shield. I have found through experimentation that cutting the width of the Scotch 24 just wide enough to not overlap when going around the coil bundle prevents the shield from being seen as a target at lower delays.

Bottom line, anything you can do to reduce the capacitance seen by the coil after the TX pulse turns off and the discharge slope energizes the targets and the damping resistor value is damping the oscillations enough so the RX stage can sample as early as possible. Less capacitance allows higher damping resistance values and potentially earlier sampling.

Joseph J. Rogowski

My point was. I get less than 10pf capacitance using magnet wire if I spiral wrap a 300uH+ coil with no spacing. Don't see how adding spacing would help. Maybe someone has tried both ways and could post results.

[Carl-NC]

I haven't tried so I don't have numbers. But your flat basket numbers suggest the improvement will be nearly zilch. And compared to everything else (FET, cable, etc), it's already in the mud.

[Op04]

My point was. I get less than 10pf capacitance using magnet wire if I spiral wrap a 300uH+ coil with no spacing. Don't see how adding spacing would help. Maybe someone has tried both ways and could post results.

I found related post by Mr Eric on vallon thread here

[Elliot]

Just a note to let people know that I have more PCB's on their way.

[Elliot]

Just a note to let people know that I have more PCB's on their way.

The batch has arrived and is through, so get in contact soon if you want one.