Beachmaster Digital

[Olly]

It is difficult for machines that detect AC to achieve good stability, because software filtering is not as good as the effect of op/AMP integrator, felezjoopi and other machines, stability is not as good as delta pulse,

I quite agree that it's relatively straight forward to filter out noise with analogue integration and filtering. If this is what you're after then there are many very good pulse induction designs on this forum that operate on this principle and I don't want to reinvent the wheel.

This is an experimental design where I'm trying to see what is achievable with direct sampling and if at the end of the experiment I find that it's just not feasible, then so be it - but I'm going to have fun trying it out along the way. It's half the fun of engineering isn't it

[jeep6789]

It is difficult for machines that detect AC to achieve good stability, because software filtering is not as good as the effect of op/AMP integrator, felezjoopi and other machines, stability is not as good as delta pulse,

[Olly]

External noise source

Hit a bit of a testing snag I'm afraid.

I've tried to make the preamp as fast as possible but am now running into serious external noise pickup problems.
Unfortunately I have one of those radar 30MPH speed warning signs just outside my house and it seems to induce an awful lot of noise into my coil.
This is what I measure directly across the coil with nothing else connected other than the damping resistor.


And this is what it looks like amplified 1000 times by my preamp.


This has not really been too much of an issue before as previous preamps have had a low enough cutoff frequency to not be too bothered with the noise.

I don't want to slow the preamp down, so perhaps it may be time to experiment with a figure 8 coil to try to reduce the noise pickup.

[jeep6789]

The 7805 is 1.5 amPs, but it heats up with a 1602 display, and the 1.8-inch LCD is even more power-hungry than the 1602

[Olly]

The 5V power chip is probably too small, because the display is a power hog

What do you base your observation on?
I have used this display with the Pico before and typical current consumption of both together from the 5V supply is around 50mA.
The +5V digital regulator can provide 250mA so even running the Pico to the max with both cores (Around 120mA) we should have enough overhead for the Pico/LCD combination as well as the audio amplifier.

[jeep6789]

The 5V power chip is probably too small, because the display is a power hog

[MartyJ1963]

Good luck in your tests! I'm sure there's a lot of others, besides myself looking forward to your test results. It's on my bucket list,,,got to learn Arduino code programming because I love the 'ANPI' developed by George and I'm sure your design is going to be a big winner too! Best regards, Marty.

[Olly]

Nice one Graham! Good looking boards,,,,and I like your Aerospace Avatar too! Regards, Marty

Cheers Marty, I hope the boards work as expected
Now starts the long-ish task of testing, developing the code and trying to characterise target decay curves (if possible).

[MartyJ1963]

Nice one Graham! Good looking boards,,,,and I like your Aerospace Avatar too! Regards, Marty

[Olly]

Are resistors and capacitors packaged in 0805

Yes, most of the resistors and caps are 0805, but there are a few which are larger e.g. the 47uF ceramic caps are 1206 and the power resistors are 2512.
The Tantalums are size A for the 10uF and size C for the 100uF.

[jeep6789]

Are resistors and capacitors packaged in 0805

[Olly]

PCBs arrived, initial checks look good - on to assembly and test - PSU first.

[jeep6789]

Good

[Olly]

Experimental Gerbers

I have been asked via private message whether I would release my experimental gerbers.
I have no problem with this at all, but with the following caveat : -

The project is still very much in the experimental stage and I haven't even received my boards back yet so I can guarantee nothing and I am not in any position to offer support as of yet.

Having said that, if anyone is interested in the experimental gerbers then here they are along with the latest schematic:-
optipulse_gerbers.zip
Beachmaster-Digital.pdf

The 1.8" LCD screen that I intend to use can be found in the UK at the "PI Hut".
https://thepihut.com/collections/pic...pberry-pi-pico

Regards,
Olly

[jeep6789]

Has anyone ever used a spider web coil? What are its advantages?