Voodoo Main Discussion

[lamoiz]

tp3 tp10 et
another scale we can see changes in the amplitude of the two signals, simultaneously .. what does this mean?

[Qiaozhi]

tp3 tp10 [ATTACH]53825[/ATTACH] et
another scale [ATTACH]53826[/ATTACH]we can see changes in the amplitude of the two signals, simultaneously .. what does this mean?
[ATTACH]53827[/ATTACH]

The first thing I noticed about your images, when compared to Fig. 3-19, is that the PI preamp is inverted. The second thing I noticed is that you appear to have the scope ground connected to the negative terminal of the battery instead of the positive. TP1 should be used as the reference point.

[lamoiz]

The first thing I noticed about your images, when compared to Fig. 3-19, is that the PI preamp is inverted. The second thing I noticed is that you appear to have the scope ground connected to the negative terminal of the battery instead of the positive. TP1 should be used as the reference point.

I did the invertions on the jumpers. actually I made all the measurements with the mass of the oscilo on the positive .. oops.
Regarding the beeps beeps between the targets, I noticed that if the threshold is at 20, the beeps disappear almost completely, what does that mean?

[green]

Just wanted to add ,
A unforeseen benefit to this coil arrangement is very little coil edge sensitivity.
A beer can has to be within 4 inches to respond.

This may really help for target separation in a small version of the coil.

Be Well

Interesting your coil has low edge sensitivity. My figure8 coil detects almost the same edge distance as centered over one of the Rx coils. Coke can, Rx_(2)133mmID fig8. 24inches centered over one coil, 22inches from the side(same plane). Probably not good.

[Qiaozhi]

I did the invertions on the jumpers. actually I made all the measurements with the mass of the oscilo on the positive .. oops.
Regarding the beeps beeps between the targets, I noticed that if the threshold is at 20, the beeps disappear almost completely, what does that mean?

Is your preamp output now the correct polarity as shown in Fig. 3-19?
I don't know what's causing the beeps at the moment, but the preamp output looks clean. Let's make sure the preamp output is OK first before moving on.

[lamoiz]

Is your preamp output now the correct polarity as shown in Fig. 3-19?
I don't know what's causing the beeps at the moment, but the preamp output looks clean. Let's make sure the preamp output is OK first before moving on.

no, I don't understand anything anymore ... I can't reverse the output, moreover my oscilo is showing signs of weakness, it's not my best day pff, I don't even have 0v with r30, and the curve s reverse. it's a mess

[Altra]

no, I don't understand anything anymore ... I can't reverse the output, moreover my oscilo is showing signs of weakness, it's not my best day pff, I don't even have 0v with r30, and the curve s reverse. it's a mess

I don't know any details about this project, but it appears your coil wires are reversed in some way. That's why your pre-amp output is reversed.

[MartinB]

The first thing I noticed about your images, when compared to Fig. 3-19, is that the PI preamp is inverted. The second thing I noticed is that you appear to have the scope ground connected to the negative terminal of the battery instead of the positive. TP1 should be used as the reference point.

Hi George
I have notice that you have referred to TP1 as a reference point on more than one occasion. Looking at my board TP1 is not actually connected to anything else. Same on the Gerber files. Am I missing something? My board is REV-C from Silverdog

[surfdetector]

Hi George
I have notice that you have referred to TP1 as a reference point on more than one occasion. Looking at my board TP1 is not actually connected to anything else. Same on the Gerber files. Am I missing something? My board is REV-C from Silverdog

TP1 is 0 volts and is the ground point. If you test it there is continuity with the +12V @ PL11 pin 1

[MartinB]

TP1 is 0 volts and is the ground point. If you test it there is continuity with the +12V.

Thanks surfdetector,
Eyesight is not so good these days, even with spectacles. Had look with a magnifier and confirmed my error.

[Qiaozhi]

Hi George
I have notice that you have referred to TP1 as a reference point on more than one occasion. Looking at my board TP1 is not actually connected to anything else. Same on the Gerber files. Am I missing something? My board is REV-C from Silverdog

Thanks surfdetector for providing the answer.
TPI is connected to the ground plane on the bottom layer. As stated on page 28, TP1 (0V) is connected to the positive battery terminal.

[Qiaozhi]

no, I don't understand anything anymore ... I can't reverse the output, moreover my oscilo is showing signs of weakness, it's not my best day pff, I don't even have 0v with r30, and the curve s reverse. it's a mess

You can set the polarity of the PI preamp using the jumpers PL7 and PL8. To double-check, I opened my Voodoo detector and had a quick look. PL7 has pins 2 and 3 connected, and PL8 has pins 1 and 2 connected. You can also see that in Fig. 4-4. This means the first-stage is inverting, and the second stage is non-inverting. Unfortunately I stated on page 19 that it was the other way around for the Troy coil. Try swapping the jumpers over. That should solve the problem.

Sorry about that.

[MartyJ1963]

Hiya George,,,Can you tell me if I've labelled this diagram correctly please? I got a little confused when you mentioned the jumper pin changes of PL7 and PL8 so I just wanted to make sure my diagram is correct for my own building reference. Thanks, Marty.

[6666]

Hiya George,,,Can you tell me if I've labelled this diagram correctly please? I got a little confused when you mentioned the jumper pin changes of PL7 and PL8 so I just wanted to make sure my diagram is correct for my own building reference. Thanks, Marty.

All that should be on the silk screen.

[Qiaozhi]

Hiya George,,,Can you tell me if I've labelled this diagram correctly please? I got a little confused when you mentioned the jumper pin changes of PL7 and PL8 so I just wanted to make sure my diagram is correct for my own building reference. Thanks, Marty.

Yes, that's correct.