Voodoo Main Discussion

[Qiaozhi]

Hi George,
What size Damping Resistor did you use for the Fisher F75 coil? Thanks

Unfortunately I didn't record the damping resistor value for the various coils. I sort of expected everyone would use the damping resistor tool to determine the correct value for themselves. However, I did find that most of the coils were critically damped with either 470R or 680R. Since the Fisher coil has an inductance of 696uH, I suspect it was 470R. Since the TX circuit uses active switch-off for the mosfet, I found that damping resistor values tended to be higher than with passive switch-off circuits such as the Baracuda.

[lamoiz]

I have adjustment problems, the PI coil used is made of silicone wire, and .430uh, r 2.2ohm, damp 650ohm; a test on the felezjoo measures a delay of 14us .. it is a rectangular coil, the tp3 signal on the oscilo is not good .. I will take pictures of all this ..

[surfdetector]

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.

Hi George,
What size Damping Resistor did you use for the Fisher F75 coil? Thanks

[lamoiz]

disc channel, ok .. but now we have to make a real coil, for the moment the tests were done with recuperated coils. where are you?

[lamoiz]

PI mode is ok, with a coil of 0.4 mh, I move on .. after the aperitif ..

[zakari]

hi
thanks george for your explanation. i cant make this circuit because ebay and amazon dont have service in my country.and i cant buy your book
this year the component is very expensive in my country. i am only checking this thread and enjoy from your knowledge and member's progress

best regard
zakari

[MartyJ1963]

Great job on the Coil Godigit! Looking forward to seeing your results. When you have time, could you give us a rundown on the build process of your new coil please? I'd like to have a go at it too,,,Thanks, Regards, Marty.

[MartyJ1963]

Nice work Lamoiz! Regards, Marty.

[godigit1]

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.

Hi Qiaozhi,

The outer two coils are 359 uh combined inner coil alone is 135 uh the RX coil is .993mH,
this coil was designed in thought only for the Voodoo.

I'm done experimenting at this point I have multiple coils styles to try on the Voodoo but im going to build one of these in Pi values to test performance on a working PI.

About both coils needing to be the same inductance, I think it depends on where the two coils will cross. Meaning the closer matched they will have a nicer overlap and bigger lap if rx is smaller . Smaller lap if inductance is higher as in the Test coil.
More about that in time if it does well on a PI.

Take Care

[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 ....

[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.

[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.

[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

[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

[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.