Voodoo Main Discussion

[6666]

then PULSE on the screen

Is that all that is on the screen ?
so this happened after you made changes in the settings ? are any of your buttons stuck down ? maybe you have hit a dead end in the code ?, but this is Georges baby,
as you have declared the chip dead even thou it is displaying some characters from within the software, I wonder if the chip would re program.

[MartinB]

Curious if you have both your +5V and -5V still?

Hi Surfdetector
I have -5v but not +5v because I do not have the sync pulse from the pic to drive U8. I have swapped out both voltage regulators U6 and U7 just in case but it made no difference.
Battery voltage is 12.1V and sensor battery voltage on pic pin 10 is 4v but there is no battery voltage display on the LCD. I have ordered a replacement LT1054 for U8 but that won't be with me until Wednesday.

[surfdetector]

Looks like the PIC on my Voodoo as stopped working. This afternoon I was playing with a new coil and scrolling through the Pulse settings when the display locked and push buttons had no effect. All I get on rebooting the board is the initialisation screen and then PULSE on the screen. There is no sync pulse on TP9 and no de-bug pulse. Has anyone else experienced this. If so, what was the cause. Thanks

Curious if you have both your +5V and -5V still?

[MartinB]

Looks like the PIC on my Voodoo as stopped working. This afternoon I was playing with a new coil and scrolling through the Pulse settings when the display locked and push buttons had no effect. All I get on rebooting the board is the initialisation screen and then PULSE on the screen. There is no sync pulse on TP9 and no de-bug pulse. Has anyone else experienced this. If so, what was the cause. Thanks

[SilverSurfer17]

Lol that makes 3 different sites its on

[dfbowers]

On that post that i was coping that coil off of he said this For the tricky part - When the bucking coil is wound around the Rx coil opposite direction from the Tx coil, the frequency goes up by about 60Hz, so a turn or 2 will have to be added to the Tx coil to bring the frequency back down to 6.59kHz. After tuning and nulling, the inner ring is filled with slow cure epoxy.

https://www.geotech1.com/forums/atta...3&d=1363497090

[dfbowers]

Right.. I might have written that document a few years ago. That build was for a White’s compatible coil where the frequency of the coil is dependent on the LC combination. The bucking coil will reduce the overall TX inductance and it’s a balancing act to get both right. I assume you are going off that document for building a coil for a hybrid or Voodoo? In that case I don’t believe that the TX inductance will matter that much as the coil is driven and a damping resistor is used instead of a tuning capacitor. The RX coil is the one you need to worry about tuning.

[SilverSurfer17]

Im curious why you didn't connect pin 1 and 5 on the pcb instead of in the connector ?

[nickel_n]

Haha.. You noticed. I went about 6 1/2 turns for the bucking coil until it nulled, and since it's an open center shell I could not return the wire directly to the ending point across the center . But.. I found out if I thread it through a spoke and double back same way that the main TX coil runs it has just a minor effect on nulling. The rest can be fine tuned with a small loop.

I LOVE YOUR WORK

[SilverSurfer17]

On that post that i was coping that coil off of he said this For the tricky part - When the bucking coil is wound around the Rx coil opposite direction from the Tx coil, the frequency goes up by about 60Hz, so a turn or 2 will have to be added to the Tx coil to bring the frequency back down to 6.59kHz. After tuning and nulling, the inner ring is filled with slow cure epoxy.

[dfbowers]

Thanks for the CC tip, what is the blue wire at the bottom of picture in the spoke next to the white object ?

Haha.. You noticed. I went about 6 1/2 turns for the bucking coil until it nulled, and since it's an open center shell I could not return the wire directly to the ending point across the center . But.. I found out if I thread it through a spoke and double back same way that the main TX coil runs it has just a minor effect on nulling. The rest can be fine tuned with a small loop.

[6666]

Thanks for the CC tip, what is the blue wire at the bottom of picture in the spoke next to the white object ?

[dfbowers]

Do you test with deep null or not?

I'm in the process of building my second concentric now.. One thing that Carl mentioned a while back but didn't pay much attention to is that many coils will null at a slightly different place at different frequencies. I find this to be true... With my coils, rearranging the fine tuning loop will bring things back into check if the frequency is changed. I think I nulled my first coil at 18kHz but it will run just fine at 10kHz too at reduced gain.

For example, the circuit I posted for my analog version is only running a gain of 5 for the preamp . I can easily increase the gain of the preamp to 220 by adjusting the fine tuning loop, and the disc channel becomes extremely sensitive. As long as the RX signal does not get clipped things are fine.. I don't think that kind of gain is needed for this project though as it's very easy to match the disc channel sensitivity of the PI section, even at low gain, which allows some flexibility. My fine tuning loop only needs to be move 1/4 inch or so to adjust the null from 18K to 10.5K. See attached..

Another thing that I didn't completely understand in the past is probably what I think is referred to as "null phase". By over coupling or under coupling it changes where the sample must be taken. It can change as much as 20uS because the polarity from the phase change will flip as it goes from under coupling to over coupling. It doesn't matter at all though as long as the sample delay can be adusted properly. With the TGSL project it didn't seem to matter, but here it does.

Also, with potting these concentric coils I find it useful to do multiple smaller pours as when things cure, small adjustment can still be made. About the 3rd pour I will finalize the position of the tuning loop. It all looks ugly at the moment but will look fine when finished.
Don.

[6666]

One thing I noticed with Youtube. If you click on the gear symbol and change your video setting, you can change the resolution all the way to 1080p. That should clear up the video.
It took me a while to figure that out.
Don..

Thanks Don, did not know you can do that, will check it out,

WOW that 1080 makes a big difference, now on my 19 inch monitor with win10 PC, I can see the meter movement .
on my laptop 780 was as high as I could go before it locked up

[dfbowers]

Thanks Don, but having trouble seeing the meter movement, bit too far away, is that your home-made coil ?

One thing I noticed with Youtube. If you click on the gear symbol and change your video setting, you can change the resolution all the way to 1080p. That should clear up the video.
It took me a while to figure that out.
Don..