Voodoo Main Discussion

[surfdetector]

Could you say which F75 coil you have thanks
https://md-hunter.com/wiki/fisher-f75/

This is the one:

https://www.kellycodetectors.com/catalog/11-dd-search-coil-f70-f75

[Qiaozhi]

Hi Qiaozhi,
Can I omit the resonant capacitor in my coil if my free running SRF in my Rx coil Is 7.8 Khz ? I may try to design a free running 10 .5Khz but if I don't have to go there it would be nice .

Still trying to learn Vlf Coils.

Thanks

I wouldn't rely on the SRF of the coil to determine the RX frequency, but you could always try it and see what happens.

[surfdetector]

Looks like the Voodoo pre amp is capable of sub 10 us sampling as tested in Pi mode. i was wondering if my coil was going to be too fast but its right at 7 to 8 us as the voodoo is in my testing.
The !8 dual field DD is capable of hitting a one.2 gram nugget at 4 easy inches and a two gram 10 K ring at 12" with a nice response on a MPP.
Thinking this looks good for the Voodoo if I can keep the Rx As fast.
.

Hi, I am unclear if you are testing your DD on the Voodoo at this time or currently just on the MPP? I would like to see a scope shot of the pre-amp output if possible. Your experimentation is very interesting to follow.

[ivconic]

I don't know what happened in meantime... but today just for fun i tried again to build from source in mikroC PRO for PIC 6.6.3 and it DID !??
No errors. Builds fast and fine.
So i flashed 18F45K22 on "Ready for PIC" board.
Ok, i assume when put in detector hardware; some functions will probably misbehave due differences between 18F4520 and 18F45K22.
But this is at least something. Now i am sure i can use this development board for flashing 18F series.
Also i can compile and build the code with mikroC PRO for PIC 6.6.3.
As completely AVR user i see this as successful attempt.
I was thinking to buy Pickit3 programmer especially for this project. Now there is no need. "Ready for PIC" is finishing the job just fine.




To make this to work i had to change few lines in the code.

Instead of this:

// LCD assignments
sbit LCD_D4 at RB3_bit;                          // Data line 4
sbit LCD_D5 at RB2_bit;                          // Data line 5
sbit LCD_D6 at RB1_bit;                          // Data line 6
sbit LCD_D7 at RB0_bit;                          // Data line 7
sbit LCD_RS at RB5_bit;                          // Register select
sbit LCD_EN at RB4_bit;                          // Enable


// LCD Port direction
sbit LCD_RS_Direction at TRISB5_bit;             // Register select
sbit LCD_EN_Direction at TRISB4_bit;             // Enable
sbit LCD_D7_Direction at TRISB0_bit;             // Data bit 7
sbit LCD_D6_Direction at TRISB1_bit;             // Data bit 6
sbit LCD_D5_Direction at TRISB2_bit;             // Data bit 5
sbit LCD_D4_Direction at TRISB3_bit;             // Data bit 4

I had to put this:

// LCD module connections
sbit LCD_RS at LATB2_bit;
sbit LCD_EN at LATB3_bit;
sbit LCD_D4 at LATB4_bit;
sbit LCD_D5 at LATB5_bit;
sbit LCD_D6 at LATB6_bit;
sbit LCD_D7 at LATB7_bit;


sbit LCD_RS_Direction at TRISB2_bit;
sbit LCD_EN_Direction at TRISB3_bit;
sbit LCD_D4_Direction at TRISB4_bit;
sbit LCD_D5_Direction at TRISB5_bit;
sbit LCD_D6_Direction at TRISB6_bit;
sbit LCD_D7_Direction at TRISB7_bit;
// End LCD module connections

Since previously i wired up the LCD according to LCD example that came from ME.

[ivconic]

Wow!
There is a eastern egg hidden in the code!
Press all the buttons together and switch it On.
Than it displays this:

[kt315]

There is a eastern egg hidden in the code!
----

[Qiaozhi]

Wow!
There is a eastern egg hidden in the code!
Press all the buttons together and switch it On.
Than it displays this:

[ATTACH]53972[/ATTACH]

Very funny.
But you've spelled "stolen" incorrectly. "Stollen" is a traditional German fruit bread that is eaten during Christmas.

[ivconic]

There is a eastern egg hidden in the code!
----

Vomiting?!
Oh no!
It is covid!
URGENTLY you must drink glass of bleach to save yourself!
Hurry up, minutes are in question!

[godigit1]

I wouldn't rely on the SRF of the coil to determine the RX frequency, but you could always try it and see what happens.

Thanks Qiaozhi,
I may try it see what happens look at the q between both ways if it works.

[ivconic]

Very funny.
But you've spelled "stolen" incorrectly. "Stollen" is a traditional German fruit bread that is eaten during Christmas.

Me?
Nooo!
I guess this is due incompatibility between 18F4520 and 18F45K22!
I'll have to obtain 18F4520 to straight this up!
BTW it makes sense.
When you put it in sentence properly than it says:
"It is traditional German fruit bread by Q !! "
But there is no place in 16 characters line for this.
...
All the troubles started because you didn't want to share with me you version of mikroC PRO for PIC!
Look what you have done!

[ivconic]

Now bit more serious.
I think i discovered why previously i had problems to build the source with mikroC PRO for PIC.
It is not about the version at all.
My 6.6.3 version would work just alright as it works now.
But earlier i didn't install mikroProg Suite For PIC along with mikroC PRO for PIC.
Although i really don't need mikroProg Suite For PIC, since i don't have supported programmer for it.
I flash 18F45K22 with mikroBootloader v2.1.0.0.
When i start mikroProg Suite For PIC; it can't recognize the "Ready for PIC" dev board at all.
So i unistalled mikroProg Suite For PIC for that reason, no use from it.
But than mikroC PRO for PIC is not building the source!? Don't produce HEX file at all.
So today by very random and fortunate coincidence i again installed full package; mikroC PRO for PIC and mikroProg Suite For PIC.
And since than; mikroC PRO for PIC started to build and produce HEX files.
Those two are in separate folders. On skim look not having any mutual dependencies.
Yet... there must be something that mikroC PRO for PIC uses from mikroProg Suite For PIC...
otherwise i can't explain it different than that.
Previously it didn't work and today is working flawlessly on several attempts.

[godigit1]

Hi, I am unclear if you are testing your DD on the Voodoo at this time or currently just on the MPP? I would like to see a scope shot of the pre-amp output if possible. Your experimentation is very interesting to follow.

Hi surfdetector,
I am at the preamp stage of the voodoo tonight i will progress.

I tested the Voodoo preamp with a 300 uh 30 awg flat planar coil I knew was pretty fast.
Just trying to get a idea of the Pi front end portion of the voodoos capability.
the following shot is with a Maxim 412, I also tried a 4562, it was faster but it wasn't as clean.



I have only tested the dual d on the Mpp but I took off my preamp and went to stock except for a 4562 amp.
this shot is of the coil balanced on a signal gen it worked pretty well but further testing and playing with the Rx coil I was able to get a little better performance bringing the nugget into play.
This coil is pretty forgiving I can even stack the rx right on top of the inner tx.
I don't know what to even call it it could be considered everything from a omega to a concentric and dual d. All depending where you put the Rx coil.
I'm building two larger size Rx d coils to see what happens to the depth and sensitivity of this coil where the trade off is.




Thanks again for the great job on your videos.

[6666]

RE Concentric coils
I re read the Dave Emery tutorial on how he makes his coils, and I noticed that he nobbles his TX coil with a 22 ohm resistor, anybody tried this ?
I put a 22 ohm resistor in a sim, and it knocks the fly back voltage from about 700 volts down to about 220 volts so will effect performance somewhat
but helps the nulling I guess.
Did a search on the forum to see if there was any chatter about this 22 ohm resistor and found some old info on vlf coils that dont have internal caps that may be usefull
and will post here for reference.
Coil pinouts

Winding, followed by pins (pos,neg), followed by inductance, and finally DC resistance.

White's Spectrum
Rx 1,2 36mH 123 ohms
Tx 4,5 540uH 1.4 ohms

White's 6B
Rx 1,2 16mH 35 ohms
Tx 4,5 1.7mH 7 ohms

White's DFX concentric
Rx 1,2 13.8mH 36 ohms
Tx 4,5 540uH 2.7 ohms

White's DFX DD
Rx 1,2 14.2mH 55 ohms
Tx 4,5 680uH 3.5 ohms

Tesoro concentric
Rx 3,4 6.2mH 22 ohms
Tx 1,5 5.7mH 22 ohms

Tesoro early Lobo DD
Rx 1,3 1.35mH 12 ohms
Tx 2,4 10mH 55 ohms

Fisher CZ
Rx 1,2 6.8mH 30 ohms
Tx 3,4 1mH 2.8 ohms

Most numbers are based on several coil measurements, including different size coils for a given coil type.

The White's 6B coils are really easy to find, and come in a huge range of sizes.

- Carl

Fisher 1210
Rx 6,48mH / 15,3 Ohm
Tx (1,64mH / 7,7Ohm) + (1,62mH / 7,5Ohm)

Fisher 1266
Rx 10-10,4mH / 38,2-39,3 Ohm
Tx 2,14-2,2mH / 4,7-4,9 Ohm

Fisher Quick Silver
Rx 6,69-6,7mH / 31-32Ohm
Tx 0,945-0,960mH / 3-3,1Ohm
Tesoro concentric
Tx 1,5 5.7mH 22 ohms
Rx 3,4 6.2mH 22 ohms
====
Tesoro early Lobo DD
Tx 2,4 10mH 55 ohms
Rx 1,3 1.35mH 12 ohms
====
Tesoro
Name TX-L TX-R (ohms) TX-fo TX wire RX-L RX-R (ohms) RX-fo RX wire
________________________________________
Brown 8" 5.59mH 21.2 --- --- 6.23mH 22.1 ---
---
Lobo 5x10 9.93mH 50.5 --- --- 1.33mH 10.97 --- ---
Lobo 8x15 10.52mH 62.8 --- --- 1.37mH 13.13 ---
========
Troy Shadow
Name TX-L TX-R (ohms) TX-fo TX wire RX-L RX-R (ohms) RX-fo RX wire
________________________________________
X2 S-9 9" 5.72mH 23.6 --- --- 6.25mH 25.2 --- ---
X5 7" 1.067mH 4.33 --- --- 6.53mH 32.2 --- ---
X5 9" 1.044mH 4.45 --- --- 6.50mH 32.7 ---
---
X5 1.1mH / selfrez = 255kHz 6.5mH / selfrez = 87kHz

[MartinB]

no, i have to watch my money because of my chemo and bills right now, i had to retire because of this disease. so only have SSI

Hi Matt
Don't quite know how to do this, but if you can get your address to me, I will purchase a copy and post it on to you. Sounds like you have a lot going on at present.

[TH'r]

no, i have to watch my money because of my chemo and bills right now, i had to retire because of this disease. so only have SSI

Sent you a PM