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.