Voodoo Main Discussion

[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.

[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.

[Qiaozhi]

Interesting experiment.

[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.

[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..

[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

[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.

[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.

[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]

Thanks George,,,Will do. Just completed the STEP 3:- LCD/Buttons stage. I can't install the LCD wiring and Button wiring until I have measure the wire length I need from my enclosure, along the shaft and up through the handle. Thanks again George. Regards, Marty.

[zakari]

hi all
Tanks george for this interesting project can you explain j1&J2&J3&PL7&PL8?
and the hex is demo or full?

best regard
zakari

[godigit1]

Don't think it will ever balance.

Hi Carl,
I actually got it to work.
Just for a learning experience I decided to give it a go.
I used two 4"rounds to simulate the d coils as I didn't have any small DD coils
.First I balanced the two smaller coils as a double O set up .
Then I added a outer 11 coil and wired it as a dual field to the Tx half of the OO set up.
When I fired it up indeed it was way out of balance but all it took was a rebalance and it zeros out easier than a concentric.

Here is the coil and a scope shot. the first balance with out the dual coil the coils were overlapped by about a third they ended up just at edge
overlap as in the photo to balance.





Best Regards

[Qiaozhi]

Well I am surprised, but thinking about it ... the outer loop affects both of the inner two coils equally.
For this configuration to balance, the two inner coils must (I assume) be exactly the same inductance.

[Qiaozhi]

hi all
Tanks george for this interesting project can you explain j1&J2&J3&PL7&PL8?
and the hex is demo or full?

best regard
zakari

Jumpers J1-J3 are only there for experimental purposes or for future options. They are unused by the current software version
The purpose of PL7 and PL8 is explained on page 19.
The book also contains the source code (explained in detail), and the hex code was generated from that. There are no time-outs or other trickery in the firmware.

[lamoiz]

It's going well, I'm disappointed, I no longer have a jumper for pl7.8 pff I will take those of the pickit ... the coil is on track too ....