Make a very simple test for me

[_q12x_]

My last night progress:

The fv Counter is reading the output of the frequency divider and is reading 1/100 = (around) 8.5Hz
(The osciloscope reading is intermittent for this 8.5Hz output, not the same every time)
The osciloscope shown here is reading the output of the PWM at 850Hz

And now, Im building the board of the frequency divider:

 

[_q12x_]

Mister @marconi and @pc1966 , in my post #73 I had a problem:
"..I might have to make a second circuit that will split another 1/10 from this one that is 1/100 and in the final output will get 1/1000. And I expect it will be extremely jumpy at that Very High resolution. If it is a way of "average" all these jumpings, especially at 1/100 stage I am right now. That will give a good clear chance for the 1/1000 stage. Hmmm. But it is in plan. For now, I have to reach that 1/1000.. "
- Can you give me an answer to this problem?
I have an idea but I think is a bit too complicated.... and is incomplete as well.
I want to see what are your thoughts.

 

[marconi]

Impressive progress and great dedication.

 

[_q12x_]

deleted post ______

 

[_q12x_]

Impressive progress and great dedication.

True, true,
The same to you
haha

 

[marconi]

To use a 555 as a frequency divider of a known and constant frequency pulse train you have to make sure that the 555 is ready to be triggered again after n input pulses where n is the division factor.

This means that one has to ensure the 555 output (shown in green) has changed to zero after a further n input pulses (shown in yellow) since it was last triggered so the 555 is ready to be triggered again by first pulse of the next group of n pulses.

The way the 555 retriggerable monostable circuit operates to divide by n means that the time constant/period of the monostable 555 - x - must satisfy this equation:

(n x T) - t < x < (n x T)

What this says is the 555 output must transition to zero after the trailing edge of the nth pulse and before the leading edge of the (n+1)th pulse - that is in the gap between them when the input is zero.

Attached is an example for a divide by 3 scheme which shows the meaning of n, T, t and x.

It is probable better then for your PWM input to keep t short with respect to T so that there is a relatively big time gap between input pulses so that variations in the 555 timer function which creates the interval x will generally fall clearly after n pulses and nicely before the (n+1)th.

Or something close to this explanation - I am bit rushed.

 

[_q12x_]

So... no answer. Ok.
And I finished the board. it took me exactly 3h to make it (continuous work, no brakes).

Is the small right (card)board

Not bad !
Now I can make another division, 1/10 to get a total of 1/1000.
It would be nice if you could look over the "average" problem, but... you are busy as well I guess.
I will probably not implement it, but it will had give me a very clean result in the final stage....
As I said, we'll see after I finish the whole 1/1000 process then.

 

[marconi]

So... no answer. Maybe not the complete answer you were expecting but something for you to consider. The explanation suggests pointers on what you might do to 'tweak' your design so that division by n actually occurs in the real circumstances of the circuit when the input period T and pulse duration t are varying randomly and the monostable duration x is subject to random lengthening and shortening in time. In plain English/Romanian make sure the on to off ratio of the input pulse stream is less than 5%(say) and n is high.

 

[_q12x_]

I still don get it.... make me a clear circuit... or a continuation of the one that I have already, Like another module to add after the last 1/100 output (that Im actually measure with the fv counter).
Draw on paper and make a picture and post it.

 

[marconi]

I and you do not know whether the variation in division result is due to variation of the input from your PWM circuit or in your 555 divider circuit or both. All I can say is the variation becomes less significant if the mark-space ratio of the input is low and n is higher. That is how the mathematics works.

To do the averaging one would need to store values over an interval which can be done but at the moment I do not think you have the ics to do that. When my parcel arrives maybe but then you can do the division in a much more practical way to not bother.

 

[_q12x_]

I and you do not know whether the variation in division result is due to variation of the input from your PWM circuit or in your 555 divider circuit or both.

That is true. We cant know for certain. BUT...my very best guess, is this signal, created by the PWM is like a picture of 800x600. When you look at it from afar, from distance, it looks detailed and good to watch, and no problems, right? Now, when I add a magnifying glass, which is our "splitter"/ fv divider here, that is magnifying by 100 times in my practical case (1/100), NOW we can see the bloody pixels in that image. Right? So again, my best guess, the source of the signal is good to a point or to a magnification. After that is crapping itself down. But...
- Doesnt matter from where is the source !!! We must add a "silencer" / "a filter" that will let flow only the important thing.
Again, im not the math guy here so you'll have to understand this aspect about me. Im better at visual representation more than anything. Im trained on it all my life actually.
My idea that is not finished yet, but I will expose it as unfinished as it is, is the folowing: we dont go in the range of 10Hz to 6Hz where the fluctuations are the worst. We go a bit higher. Let's say to 20Hz just to be sure. Right? Now, from this "sure" position, we can start trim and cut and filter what we need and send out only a constant flow of impulses at 20Hz and the rest of fluctuations trim off or avoided somehow. And this is where my idea stops.
Actually it is in my plan to try a very simple approach, like we deal with 240V filtering, after all this is also a fluctuating current, right? and I will add a filtering capacitor in the output of this fluctuating crapping itself signal. It is in plan, I have to try it. This is the simplest idea I could think.

 

[_q12x_]

Hmmm. I managed to clean the output of the PWM and get a VERY stable output reading from the fv counter for the 1/100 level.
But I could not make it to 1/1000. I tried many ways.
First I hooked up the 1/100 board I just built to the breadboard with a 1/10. And it kept showing me the same output as the input. Very-Very strange. Logically you would expect another division. But noooo.
Then I said, blaimy, I leave only the breadboard circuit and tried to bring it down to 1/1000 as a single circuit. It didnt work because the fv counter can't count 0.x x x fv. It just stops at 0 and thats it. It actually jumps from 8 to 0. The most I could get it down was 2Hz, and I thought on a logical RC arangement of values to try for the 1/1000, that it wasnt working for the fv I had to test with, but MAYBE, it will work with the crystal.
Then I hooked up the crystal and ... nothing. I put it at 1/100 and it should have giving me something around 200kHz, what the maximum of this device could see, I was hunting for some variations at the border, but nothing. Then I tried a 14MHz crystal with also 1/100 model and it should had shown something. And it didnt. Then I tried my theoretical RC values for 1/1000 and nothing worked either. Also put both crystals and again, nothing. It was staying on 0 Hz all the time.
Then I measured the output of the circuit, oh, I used your circuit mister @marconi with 1 transistor, and it give me 4V, so it was an output from that, no doubt.
I made so many permutations today, I am tired.
Funny story: I unhooked everything from the fv splitter circuit but I touched the input wire with my fingers. And the fv counter showed a clear 50Hz - hahahaha, I dont even have to plug it on the mains, I am vibrating at this fv anyway. Now that Im thinking it should have been 5Hz since it supposed to be splitting. I noticed sometimes, in certain conditions, the output is equal with the input of the fv splitter.
Then, I had another bright idea, to check the maximum fv of the 555 ! And I checked the internet, and it says "500-kHz to 2-MHz ", ok, then I looked in its datasheet and it says:

and I didnt find nowere the fv of the 555 mentioned in its datasheet. This values here, the 100ns are the only ones I could find and I thought I can convert that into Hz, and I did, and guess what, 100ns = 10000000Hz = 10Mhz . I beat the internet with this finding, but still not good enough for my 20MHz crystal. So.... Im screwed with this experiment. Its a test anyway. But I am not happy that logic splitting didnt work. It should had. I was counting on it. Eh well, life lesson, never expect anything.

 

[marconi]

Deleted post and some extra words

 

[_q12x_]

How is your progress, signore @marconi ?

 

[_q12x_]

And, we are turning back to some of my previous ideas.
My greatest suspicion is that 555 circuit could not do its job do to a much greater fv in its input than he is designed to support and see.
So....my previous idea that someone here laughed at, was to make a discrete fv splitter. We need it for a couple of times, not the entire 1/1000 range.
- So I ask again, give me your best discrete circuit that is capable reliable to split a very high fv !
My plan is simple: I will split it a couple of time using discrete fv splitter circuits, and after is down under 10MHz as the datasheet of the 555 mentioned (or 2MHz as the internet says) after that, I will input my 555 fv splitter circuit. Simple. And this is a good plan. I will do the work anyway.

 

[marconi]

How is your progress, signore @marconi ?

Good morning. I had a day off yesterday. But I was thinking about whether:

a. to use an opamp or transistor to amplify the signal;

b. to pause on (a) and make a crystal oscillator instead using a 74HC04 as Lucien did from which one can produce a square wave very easily 5V-0V to drive the 74 series divider. This approach keeps things very simple whereas (a) would require more tinkering* around. Alas I do not have as much patience as you do so prefer to keep things simple these days. I have posted you some 74LS04s and 74LS00s so it may be possible to use these instead of the HC04s. I will have a rummage now in my shed for some.

*tinker around with - https://idioms.thefreedictionary.com/tinker+around+with

 

[pc1966]

The simplest divider I can think of would need at least 3 transistors (without resorting to odd devices like the unijunction transistor), two for the state memory (i.e. flip-flop) and a 3rd to try and steer it to change state on each edge. Others seem to have the same idea as here is an example of a T-flop (scroll down the page):

Flip-Flops Using Discrete Transistors

Flip-Flops Using Discrete Transistors: Hello everyone, Now we are living in the world of digital. But what is a digital ? Is is far away from analog ? I saw many people, which believes that the digital electronics is different from analog electronics and the analog is a waste one. So her…

www.instructables.com

But, as Lucian pointed out, they end up with RC time constants that limit the useful frequency range. The example on the link above would not operate anywhere close to 20MHz due to the high-ish R and stray capacitance, device capacitance, etc.

If you get a 74HC4060 then its input gate can be an oscillator or simply an amplifier for squaring-up the output of a transistor oscillator, and then you get the dividers all working as part of the deal.

 

[marconi]

q12x Here is 74LS00 crystal oscillator which you can make when the box of ics arrives. Now you have three circuits you can make to test your crystals with.

 

[_q12x_]

Thank you signore @marconi , very good progress so far. Don't forget to actually post the circuit for this last experiment with the 74LS00 in the video. Drawing on paper is the fastest way.
To mister @pc1966 , yes I found the exact same page. Its good that you mentioned that RC limiting problem, not reaching 20MHz. Then what would a circuit be not limited? Can you guys think on creating and also testing (having all that nice osciloscopes) such a circuit for me?
I was thinking, how the light measuring devices are functioning?
What circuits they have inside that actually measure such great fv values? Yes, visible light
Electromagnetic_spectrum

Maybe we can use something that they use, you know? That's my idea. A special sensor or a special circuit.
- The conclusion so far, is that I can Not build a discrete fv divider ? That sucks...
- To be totally sincere, I didn't put quite all my energy into discrete fv divider either, I choose the fastest routes as a coward as I am, using the 555's and next the IC's are about to come. It bugs me the 555 is not up to the task. Aaah.
- The 20MHz osc is the test osc ! I have other osc at different fv, some are greater some are less. I have one for ex at 40MHz. So our circuit must read up to 100MHz or more, to be able to deal with all the common osc values. I also have a lot of unknown values, which was the starting point for all this adventure here. Keep this little detail in mind all the time. FUN, right? Hahahahaha.

 

[marconi]

q12x Here is 74LS00 crystal oscillator which you can make when the box of ics arrives. Now you have three circuits you can make to test your crystals with.

Here is the circuit which uses three of four 2 input nand gates in the 74LS00. The fourth gate is unused so its two inputs are connected to 0V so that they do not float. The crystal is in the series resonance mode so low impedance at 20MHz.

I will look at the ics in the box to you and think about which one to use to do the division of fv and then construct the circuit. I am a bit slower off the mark than you are so be patient. I like to read the datasheets. I quick glance at the 74LS93 4 bit counter specification and it looks like it can operate the first divide by 2 stage with an input between 32 and 42 MHz so it might cope with your 40MHz crystal if the crystal test rigs will still perform at 40MHz. The last circuit using the 74LS00 was oscillating at 32MHz without the crystal in circuit - need to check again though to be sure.

https://www.ti.com/lit/ds/symlink/sn5400.pdf?ts=1653117913729