AMX TX

[ivconic]

If I didn't see it 16 years ago, it's certainly because I didn't see much interest in it, otherwise I would remember it.
Just because I don't write a lot of posts doesn't mean I don't look at posts....
And I may have several accounts who knows... My first design 30 years ago now approx
Come on, I'll stop bothering you
I'm going to have to calm down because here I am on my 39th message!

You don't bore me a bit, on the contrary; I'm so glad there are still people alive here!
Yes, I think you hit the spot; many (like you) just keep quiet and watch what's going on.
And they can't even write anything.
If you followed the initial posts on the topic of the AMX project (God kill me if I know why they called it that)...
well, if you followed the initial posts; then you probably read that we debated a lot about the choice of hardware.
In the beginning it was a question of direct sampling or analog integrators.
For direct sampling, "heavy machinery" should be picked with a lot of resources.
And that is a technology inaccessible to many, for one reason or another.
That's why I advocated another approach, analog integrators and the signal "chewed" to the end, and only then introduced into the MCU.
In that case, even a more modest ADC would get the job done. Modest MCU too.
And at the very beginning it was said that we would vote for one of the options.
Suddenly one day I come to the forum and see that they have already "voted" and chosen the first option; direct sampling.
How did you vote? Where? When? Who?
I don't know, but I see that the second option has been removed and that the first one, direct sampling, has been selected.
Then we continued the debate about the choice of ADC chip. There was no consensus there either. Because the megalomaniacs prevailed.
And while you slapped your palm against your palm; silence... after weeks of heated debate... suddenly silence.
Carl shows sporadically and says that the work is already underway!??? "Works"? What "works"?
And so... I had to make an extra effort and risk getting on many people's nerves;
in order to "pluck out" a couple of rather incoherent pieces of information from Carl.
I know Carl from before, it's difficult with him.
When you provoke him enough;
then there is no better person than him and his explanations are somehow the best and easiest to understand and learn from.
But you have to put in a lot of effort to get there, play the fool and get on everyone else's nerves.
So now, you too were provoked enough to show up. What have you been waiting for? Didn't you have anything to write long ago on these topics?
Do I always have to be the only "bad, boring and avoidable" one here?

[Asgard]

I posted all that 16 years ago man! How come you didn't see that until now!??

If I didn't see it 16 years ago, it's certainly because I didn't see much interest in it, otherwise I would remember it.
Just because I don't write a lot of posts doesn't mean I don't look at posts....
And I may have several accounts who knows... My first design 30 years ago now approx
Come on, I'll stop bothering you
I'm going to have to calm down because here I am on my 39th message!

[ivconic]

Ivica, you walked into that one!

Oi Quasishohi!
Without my nagging and bothering no one here would have posted a word for weeks!
I was deliberately silent for a couple of weeks, I was making an experiment that way; and in those few weeks,
no one published a single word on these topics!
Think about such things, son... (I am trying talk like a London hobo)
Even you showed up here and you weren't there for long. I rest my case with this.

[ivconic]

I'm not American but I think if you kick everyone out you'll be on your own.
And so I wonder why you haven't sent us the right schematic yet, since it seems that alone you go faster than with the others?

In the spirit of this topic, I will answer you like this;
where are you rushing?
Slowly!
We are still young!
Life is ahead of us!
If you are in a hurry;
imagine a Nucleo dev board that will arrive in 10 days (and I told my son to send it to me about a month ago),
add to that TX from Paul-moodz&Carl and RX from .... who posted that?
Not important.
So add all those, put togather and there you have the schematic!
The schematic part is on the xyz topic, post #12/3, the second part is on the zyx topic, post #14650... etc.
I posted all that 16 years ago man! How come you didn't see that until now!??
I see... with your 38 posts so far... you really have the right to be comical!
You have nothing else left anyway...

[Qiaozhi]

With me, you would all be fired immediately!

I'm not American but I think if you kick everyone out you'll be on your own.
And so I wonder why you haven't sent us the right schematic yet, since it seems that alone you go faster than with the others?

Ivica, you walked into that one!

[Asgard]

BTW... it seems that anyone who sets foot on American soil; become super slow, lazy and lose the sense of obligation and given word...
My son, "speedy Gonzalez from NY", just informed me today that he just sent two Nucleo boards in the mail yesterday...
And that they will reach me in about ten days...
10 days! In 10 days I will forget what I wanted with those boards!
Actually I already forgot! Because I ordered him to buy it for me before.... I don't remember how long!
I don't know how you Americans even survive that way and with that lifestyle!??
With me, you would all be fired immediately!

I'm not American but I think if you kick everyone out you'll be on your own.
And so I wonder why you haven't sent us the right schematic yet, since it seems that alone you go faster than with the others?

[ivconic]

BTW... it seems that anyone who sets foot on American soil; become super slow, lazy and lose the sense of obligation and given word...
My son, "speedy Gonzalez from NY", just informed me today that he just sent two Nucleo boards in the mail yesterday...
And that they will reach me in about ten days...
10 days! In 10 days I will forget what I wanted with those boards!
Actually I already forgot! Because I ordered him to buy it for me before.... I don't remember how long!
I don't know how you Americans even survive that way and with that lifestyle!??
With me, you would all be fired immediately!

[ivconic]

Wake up man! This has been extensively discussed since Paul first posted the circuit here. That was 21 months ago! You will see that his sims use 1.25V or so. Mine are usually at 1.6V to get 0.5 amps, and with the diode kicker scheme it should be a little more than 2V.



Right now I'm planning on direct sampling, so a preamp and an ADC. I may do a backup plan with 8 analog demod channels.

Yup!Exactly!
You will slowly understand the point of my displeasure. Take yoour time.
You said it yourself;
21 months... and we still haven't seen half a second of video demos anything made and alive... of anything written so far.
21 minutes later; and I won't remember anything I wrote here.
Because I have 4 different things waiting on my desk that I need to do today. All are complex and all require full focus.
What I remember photographically are photos, schematics, pcbs and video demonstrations of devices that I liked how they worked... only!
...
Additional confusion arose when you mentioned the IRF740...
Even if it is a fet with a line level on the gate, and it is not, what voltage then comes to the gate?
...
So moodz's name is Paul!?
Hi Paul!

[moodz]

... and just to keep the pot bubbling. It would be nice if you could just use a constant current source for the TX circuit but you cannott because the source impedance of a current source supply is too high. ( try it and see what happens :-) )

So instead we use a controlled impedance current source with a current splitting scheme but instead of wasting the power feed it back into the power supply. ( in this case 1.5 volts ).

By doing this can achieve 0.6 amp peaks ( 1.2 amp peak to peak ) with 0.8 watt consumption and tilt correction. Loss in the power supply section was 32 milliwatt. Peak flyback was 700 volts.

The power supply is substituted as below. ( previous current boost coil removed ).

This now allows the use of practically any coil and should be on a par with Carl's solution ( which is very good also ).

[Carl-NC]

It's typically around 2V depending on FET & coil resistances. ...The buck regulator is only for the TX. It does not power anything else.
2 volts? Is it typo or 2 volts indeed? You are powering TX part with 2 volts?
I am confused here!?!?!?

Wake up man! This has been extensively discussed since Paul first posted the circuit here. That was 21 months ago! You will see that his sims use 1.25V or so. Mine are usually at 1.6V to get 0.5 amps, and with the diode kicker scheme it should be a little more than 2V.

In this kind of circuit the TX and RX are very independent of each other...
I know that. I asked from different reason; to sum up the overall number of samples (ADC channels) needed for what you planned.

Right now I'm planning on direct sampling, so a preamp and an ADC. I may do a backup plan with 8 analog demod channels.

[ivconic]

It's typically around 2V depending on FET & coil resistances. ...The buck regulator is only for the TX. It does not power anything else.

2 volts? Is it typo or 2 volts indeed? You are powering TX part with 2 volts?
I am confused here!?!?!?

In this kind of circuit the TX and RX are very independent of each other...
I know that. I asked from different reason; to sum up the overall number of samples (ADC channels) needed for what you planned.

[Carl-NC]

What is the voltage coming out of the buck regulator?

It's typically around 2V depending on FET & coil resistances. See Paul's simulation schematics.

What exactly are the fets?

I don't know yet. I've been simulating with IRF740s which work in sims because the breakdowns are not modeled.

What does "Cextra" mean and what is its role there?

Post 102: "So we can control the flyback with capacitance, which is why my schematic has a place for C_extra."

What does ADC1 and ADC2 mean , what is the purpose of those two samples? Is it "It requires sampling the flat-top at 2 points" ?

Yes, in the previous schematic I used an integrator to control the loop voltage. But now I need to sample the flat-top at 2 points to get tilt. I could do this with analog circuitry but it's easier to do it in code.

Method you described as short voltage boost with fet and the diode, actually a sort of "chopping" the voltage... any sideffects?

Don't know yet. Certainly it increases power consumption.

Will it affect the reception signal?

Should not.

Will "It requires sampling the flat-top at 2 points" correct any possible sideffects?

Don't know yet. Likely this will require some filtering to control "tracking" speed as the ground changes.

Without accompanying RX circuitry it is tough to see the whole picture.

In this kind of circuit the TX and RX are very independent of each other; there is nothing on the RX side that affects the TX side. And a decently complete RX AFE has been posted in the RX thread. At some point I'll merge them for making a PCB.

How exactly many different sampling points will be overall?

On the TX side (which is all we are considering in this thread) there are 2 sample points per half-cycle. On the RX side there will be multiple samples, which have nothing to do with the TX sampling.

What are your intentions with so many different samples?

On the RX side? Hopefully to distinguish curvature differences between eddy, magnetic, and viscous responses.

Would be good to see the "plan" explaining the use of so many different samples.

I don't have this clearly mapped out yet. Mostly it is experimental: build it & figure it out.

What are the energy losses and how they affect the quality of the reception signal?

TX losses? See post 102. It is uncertain how much they affect the RX, but it is probably a Good Idea to hedge our bets, assume they do, and correct for them.

Instead of chopping the common buck reg. output; will it be better to dedicate separate power source for TX stage?
(Is it common voltage output coming from buck reg. or it is actually dedicated power source only for TX?)

The buck regulator is only for the TX. It does not power anything else.

[ivconic]

"...Needs compensation of energy losses to guarantee the constant current..."

This is what I don't understand well.
What are the energy losses and how they affect the quality of the reception signal?
Instead of chooping the common buck reg. output; will it be better to dedicate separate power source for TX stage?
(Is it common voltage output coming from buck reg. or it is actually dedicated power surce only for TX?)
Man can't tell this without insight in whole circuitry.

[ivconic]

What is the voltage coming out of the buck regulator?
What exactly are the fets?
What does "Cextra" mean and what is its role there?
What does ADC1 and ADC2 mean , what is the purpose of those two samples? Is it "It requires sampling the flat-top at 2 points" ?
Method you described as short voltage boost with fet and the diode, actually a sort of "chopping" the voltage... any sideffects?
Will it affect the reception signal?
Will "It requires sampling the flat-top at 2 points" correct any possible sideffects?
Without accompanying RX circuitry it is tough to see the whole picture.
How exactly many different sampling points will be overall?
What are your intentions with so many different samples?
Would be good to see the "plan" explaining the use of so many different samples.

[Carl-NC]

Sorry for being gone so long, last few weeks were hectic including 2 travel trips. First, here is the missing sim as best I can re-create it. This shows the tilt at ~0.65mA, but I recall it being closer to 1mA before. In any case, it's in the ballpark of the calculation.



Second, I have been looking at some tilt correction methods, including what Paul posted. I had never considered using an additional boost inductor to correct the energy loss in the search coil, I thought that was rather clever. However, one thing I don't like about it is that it wastes a lot of TX energy in the process. Early on, I thought about giving the VTX supply a short voltage boost right after the polarity transition and I figured out an easy way to do this. Simply add a series diode to the supply and place a shorting switch across it. At each transition, briefly short the diode to boost VTX. It requires sampling the flat-top at 2 points, and the micro can handle all the work.



This method also wastes power because the regulator voltage has to be increased to account for the normal drop of the Schottky. That will be around 0.25W for Ip=0.5A. My goal for the total TX power is 1.0-1.2W for Ip=0.5A. Note that this method should work over a very wide range of TX coils which is another goal. Here is a plot of slope correction for exact correction, and +/- 10ns on the pulse width.



So the correction granularity will depend on the micro clock. The plot above suggests that a 100MHz micro will get you within +/- 10uA of perfect.