Signal synthesis for simple PI detector

[Altair]

I am a bit struggling with my oscilloscope, trying to monitor what's happening on Atmega output pin.
Yes there is a single shot, occasionally appears on the screen.
Seems my oscilloscope is not capable to measure such tiny moments.
Or... i might be doing something wrong.

Anyway; i will return to this later. Right now i am buried in bedlam of tasks which must be solved within next few weeks.
So my posting here will be random and occasional.
But this subject is very interesting and deserves special attention.

Could be you have some problem with trigger... try to set correctly your trigger channel, level and slope to catch the signal.

[ivconic]

I am a bit struggling with my oscilloscope, trying to monitor what's happening on Atmega output pin.
Yes there is a single shot, occasionally appears on the screen.
Seems my oscilloscope is not capable to measure such tiny moments.
Or... i might be doing something wrong.

Anyway; i will return to this later. Right now i am buried in bedlam of tasks which must be solved within next few weeks.
So my posting here will be random and occasional.
But this subject is very interesting and deserves special attention.

[Altair]

Dang! Blast!
COOL!
I will take time tonight to try to completely understand that!
Hell interesting!
THANKS!

My pleasure, a little contribute to your huge effort to all projects!
I have used that in my MD experimentation with great success!

[waltr]

You have a few good threads here on using Arduino for Timing in a PI detector.
These are readily available, I even have a few, and easy to code and use.

Good stuff.

[ivconic]

Ivconic,
take a look on this:

https://wp.josh.com/2015/03/05/the-perfect-pulse-some-tricks-for-generating-precise-one-shots-on-avr8/

Dang! Blast!
COOL!
I will take time tonight to try to completely understand that!
Hell interesting!
THANKS!

[Altair]

Ivconic,
take a look on this:

https://wp.josh.com/2015/03/05/the-perfect-pulse-some-tricks-for-generating-precise-one-shots-on-avr8/

[ivconic]

I agree; hardware part is weaker point here, need improvements.
As for code, when interrupt occurs; Atmega fires up the sequence which is pretty correct in timings.
I stopped there because i didn't solve the problem of "third" pwm pin which i'll need if later want to add second channel on detector.
If you analyze the sequence; you'll notice the schedule:
100uS + pot adjusted delay + 42.8125uS + 25uS + 42.8125uS + 42.8125uS = 253.4375uS + pot adjusted delay.
Plenty spare time till 1666.667us. That time can be used to play with LCD, other free pins on Atmega etc.
It's the Atmega328 architecture. I could use only those 2 pins internally tied to active timer.
I guess it is solvable. But i stopped than and never continued later.
But one thing is for sure; when sequence fires up: all the calculated times are pretty correct.
So, "9uS" are real 9uS within the sequence, unfortunately not real in hardware.

[homefire]

"'' Was it real 9uS on hardware? I do seriously doubt that. ""

The processor is doing way more then just a timing simple loop. Any other functions are causing inherent delays. All of those commands ( Execution Times ) need to be added in the over all time train.

Add up the propagation delays through all Fets and Op Amp, Transistors.

Your actual realized timing may have been a Multiple or a Fraction ( If it jumped Timing ) of your set 9uS ?

[ivconic]

"...value = analogRead(A0);..."

And on schematic is A3 used for pot reading.
So...
Correct in code:
"...value = analogRead(A3);..."

Reason for this is because i had "trillion" of versions on each of my works i did so far.
Sometimes you learn through the work. Sometimes you make skim decisions and later you forgot to correct in documentation.
But it is not a problem at all. Everything is later easy to adjust in code.

[ivconic]

Digital part is quite alright, providing pretty precise timings.
I simply replaced 40106 with Arduino and performed series of testings.
It is the "hardware" which needs a bit of improving. To be able to provide properly what's coming from digital part.
I hadn't enough time to do that. At the time.
So i got situation to adjust "1uS" sample delay at digital part. Precisely.
But i seriously have doubts that hardware really follows that.
It was back than, several years ago. Since that i did nothing on that subject.
I even had short video, posted on Yotube... than removed, by me... can't recall the reason why...
Now i can't find that video on my backup disks.
Point is; code is tested and alright. Providing quite precise timings.
Task; to work around the hardware and improve it for shorter delays.
As i recall; i got significant detection improvements on small targets at 9uS adjusted delay.
Was it real 9uS on hardware? I do seriously doubt that.
This is now open project. Public domain. More conversant people can join and try to improve the hardware part.
Welcome!

[ivconic]

Output Transister a MPSA 13 ?

I believe so. I had MPSA14 at the time.
BC517 will do the same.

[homefire]

Output Transister a MPSA 13 ?

[ivconic]

Nice but What Processor???
The processor block in the schematic is blank.

I used a PIC16F88 for my Hammer Head which does what yours does.
A processor is a great way to go for PI detectors instead of all the timer chips and allows easy changes to timing.

Atmega328P. Pinout is for Arduino UNO, Mini Pro, Nano...
Arduino IDE is the compiler.

[waltr]

Nice but What Processor???
The processor block in the schematic is blank.

I used a PIC16F88 for my Hammer Head which does what yours does.
A processor is a great way to go for PI detectors instead of all the timer chips and allows easy changes to timing.

[ivconic]

Pay attention on this: "LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);"
And the value "0x27".
It is the address of adapter used to drive parallel LCD16x2 via I2C.
Not all similar adapters are having the same address.
You'll have to find out the proper address of I2C adapter you'll use.
How?

http://www.geotech1.com/forums/showthread.php?24921-I2C-device-scanner&p=252737#post252737