Bipolar PI design

[Detectorist#1]

Hi eduardo1979,
Congratulations for you and for Carl. How hot are the two stones in your youtube video? It is interesting - you not change the GB setting pot between waving of them.

[eduardo1979]

The error has disappeared, as using a 4066 as a demodulator with its corresponding level translators worked perfectly. The VCO was also modified and replaced with a 4046. The Threshold stage was also modified. In any case, this is a project that can be further improved. For now, it detects a gold wedding ring 30 cm in the air. It also detects gold nuggets, but at a shorter distance than the TDI. As a learning base, this project is very good, giving people the opportunity to try out a Bipolar PI. Carl has done a great job, as always.

[algan]

Perfect Eduardo and you act quickly. Now can you tell me what the oscilloscope diagram is with your project? Is there still the bug that Carl showed in the video or is it gone? Can you make a clip of the oscilloscope? Thanks.

[ivconic]

Excellent Eduardo!
Dunno why Carl is "complaining", the detector works quite alright!
(Carl is too modest)

[eduardo1979]

Hello everyone.
I've finally been able to finish the PI Bipolar detector. Everything works correctly, just as shown in the video. The sound is very similar to the GPX series. The Hi-Low discrimination is very good, as is the GEB.
https://www.youtube.com/@eduardofern...pez7868/shorts

Best regards,
Eduardo.

[Carl-NC]

Carl, apparently the frequency adjustment range is very wide, going from about 330Hz to as high as 1.8kHz.
A simple question: "is it safe?"

As the frequency increases you should also see the pulse width decrease. Because the relationship is non-linear, it actually burns less power at higher frequencies.

[ivconic]

One less dilemma, thanks Altra!

[Altra]

A short answer for PI, it will not work. There are always output protection diodes on motor controllers. These connect between the coil connections and power supply rails. These will divert the flyback energy to the power supply. For a continuous wave detector vlf or bbs it may work

[ivconic]

Ok, this is not directly related to the topic, but if I don't write here now; I will forget later!
I have a "crazy" idea. How about using a finished H-Bridge module instead of the proposed TX stage?
(of course, only one clock and possible reordering of samples will be needed).
This is an idea for "megalomaniacs"!
The module is based on BTS7960B. The specs are fantastic!

- High peak current capability of min. 33 A
- Path resistance of typ. 16 mΩ@ 25°C
- Low quiescent current of typ. 7 µA @ 25°C
- PWM capability of up to 25 kHz with active freewheeling
- Switched mode current limitation for reduced power dissipation in overcurrent
- Status flag diagnosis with current sense capability
- Overtemperature shut down with latch behaviour
- Overvoltage and undervoltage shut down
- Driver circuit with logic level inputs
- Adjustable slew rates for optimized EMI

How about that ha!

[ivconic]

The question "is it safe" refers to the case if I use the proposed mosfet transistors as well as the fact that it is an H-Bridge configuration.
Maybe it's a good idea to "fix" the frequency with a fixed resistance?
It's even easier and more precise to do it in code.
But for now, it's good to have the ability to adjust it for further experiments.
I am considering some "better" P-channel transistors for now.
Hey! This is so much fun!
The goal itself, the finished detector, is not as important as the great enjoyment of the journey to the goal!
Carl I haven't had this much fun building a detector in a long time! Thank you for the project!
Although I've been terribly lazy lately... I'm too curious to repeat the measurements with the big oscilloscope!
The 10k resistor trick on all 4 samples worked very easily on the GS4... who remembers that video.
But it doesn't work on this one.
I wonder if it's because of the oscilloscope, I'll have to try it on the big one!

[ivconic]

Carl, apparently the frequency adjustment range is very wide, going from about 330Hz to as high as 1.8kHz.
A simple question: "is it safe?"

[ivconic]

Although, it is difficult to clearly see the shift in the delay on such a small oscilloscope, but it is still roughly visible.
Yes, I noticed one thing; when I set the delay, upper oscillogram, TxP; moves, while the lower oscillogram (one of 4) stands still in place.
(the 10k trick doesn't work, so I can trace only one by one)
I might have to check everything on a big oscilloscope after all.
This little oscilloscope is surprisingly good... but not that good!

[ivconic]

Have you tried the frequency control or the delay control?

Video on #231 shows exactly that.
...

Oh sorry!
The video only shows the frequency setting!
I recorded the delay, but the recording turned out bad, so I deleted it.
Yes, delay works too.

[ivconic]

Flashing the chip apparently worked.
Everything behaves as it should.
But my problems never end!
I can't finish the detector until I find the 74HCT4053, because no store in the state has it! Ha, ha, ha!
I'm 101% sure I have at least 5-6 pieces on the old boards in the attic.
But it's such a big disorganized mess; that it will take me a couple of days to find them!
And now it's the weekend, the post office won't work, so I won't get the 74HCT4316 and a few more components until the middle of next week.
For example; I don't have 0805 capacitors, I haven't put any, they have yet to arrive.
Ok, I'm used to waiting.
I noticed that the two trimmers I put in, used ones, are not working well.
I will have to replace them with quality potentiometers (like in Carl's picture).
All in all... I'm satisfied! So far so good!

[Carl-NC]

Have you tried the frequency control or the delay control?