Voodoo Main Discussion

[Qiaozhi]

Hiya George,,,Can you tell me how to test the Transmitter circuit please without attaching a coil or do I need to build the LCD/Button step and PI Preamp first/attach a coil? Thanks, Marty.

If you fit a damping resistor (without the coil) then you should see a set of TX pulses across the resistor. Without the coil there will be no feedback pulse to damage your scope probe if you forget to switch to the x10 setting.
I assume you've fitted the PIC and flashed it with the hex code? If so, then the +5V supply will be present, and there will also be a TX oscillator pulse at pin 29.

[MartyJ1963]

Hiya George,,,Can you tell me how to test the Transmitter circuit please without attaching a coil or do I need to build the LCD/Button step and PI Preamp first/attach a coil? Thanks, Marty.

[surfdetector]

Alec got me rethinking the dual field / concentric coils and here is what I came up with. Might be a good fit for this project. It?s loosely based on the Troy X5 concentric but about 1 1/2? larger in diameter. My dilemma has always been how to shield a coil in a spider shell. Any ideas??
I have an 11? form partially completed as well. Let me know if there is any interest.

Don..

Hi Don,

Those are some excellent looking spider shells. I am quite certain that I have read somewhere that the Dual Field coil could be shielded with the conventional spiral of copper tape or mesh. I am not sure concerning the concentric with its bucking coil.

[bernte_one]

@Don

mix the epoxi with graphit powder

for example if you need 200 gramm mass of epoxi (medium size drinking cup) just add 2 large eating spoons of graphite powder
the mix the very good and you can test that with multimeter (10-100kOhm per cm is ok)
you need no gap or so, like normal foil shielding

xp deus use the mix in thier coils too

[dfbowers]

Alec got me rethinking the dual field / concentric coils and here is what I came up with. Might be a good fit for this project. It’s loosely based on the Troy X5 concentric but about 1 1/2” larger in diameter. My dilemma has always been how to shield a coil in a spider shell. Any ideas??
I have an 11” form partially completed as well. Let me know if there is any interest.

Don..

[MartyJ1963]

Hi Alec,,,The reason I asked was because I was building the Voodoo in steps as suggested by George,,I.E:-Step 1 - IC sockets then Power supply,,Step 2 - Transmitter circuit,,then testing to see if it's functonal but Step 3 is the LCD/Buttons and Step 4 is building the PI Preamp and connecting a Mono coil to test the PI Mode. So I'm a little confused? Do you mean look at the signal across the 3R3 (R2) or the Damping resistor across the coil? As I haven't got to the coil stage yet? Thanks, Regards, Marty.

[Qiaozhi]

Interesting experiment.

[godigit1]

Its not pretty but I got a dual field concentric to work.
Ok so its probably not much benefit in the package I have it either but I was thinking for a large coil for the Voodoo, say 18 inches where it could be a advantage to have that smaller coil it could maybe have potential. Have to build the Detector to really know.

I used a 10 1/2 inch outer coil and 7 1/2 inner dual field coil 359 uH together, the Rx is .993mH
Both the RX and bucking coil are 4"



I was able to get it to a perfect null pinning the wires and if I took more time with the tape it could 0.
Testing at 5k 20 v peak to peak.

[surfdetector]

How can I test that the Transmitter circuit is functional please?Thanks, Regards, Marty.

You are going to look at the signal across the damping resistor with your oscilloscope.

[MartyJ1963]

Hi All,,,,STEP 2:- Transmitter Circuit complete. Next,,STEP 3:-Installing the LCD and Buttons,,,I first have to decide which enclosure I'm using and whereabouts on the Detector shaft it will sit so I can measure how much wire I need for the LCD and Buttons.
How can I test that the Transmitter circuit is functional please?Thanks, Regards, Marty.

[godigit1]

That's Why I ask Thanks Guys It Was A thought. But I think it can be done as a 3 coil concentric. Maybe a 12" 8" and 4" for the rx, two outer coils as the dual fields damped as normal Rx coil bucked off inner dual field coil should work just like a concentric.
What do you guy think about that one.

[dbanner]

Don't think it will ever balance.

Correct

[Qiaozhi]

[ATTACH]53740[/ATTACH]

Something like this. I was thinking wrapping the dual field part as you would normally except to a d style inner coil. The wraps of the inner coil could be played with a bit to get a lower transformation ratio between ds to act as a bucking coil I'm thinking and or that wont matter if it balances out like a regular DD the later preferred. the Rx DD of course would have to be phased properly.

I have enough coils around to do a experiment thinking might throw something together and see if I can get it to null.
No small DDs so I may go 12" outer round and 4" double OO for the DD portion since I have them.

Thanks again for All this .

Don't think it will ever balance.

Carl beat me to it.
I really cannot see how that configuration would balance. Obviously the 2 DD loops will balance on their own, but then you've added a large TX loop around the outside that upsets everything.

[surfdetector]

Hi All,,,Found time between repairs to install STEP 1:-The Voodoo Power Supply and TP1,TP9,TP14, TP15 + PL9. STEP 2 will be The Transmitter Circuit. Regards, Marty.

Looks good Marty,
I will be starting mine on the weekend.

[Carl-NC]

Don't think it will ever balance.