crutschow
ok thank you i will change the comparator to increase the % dutycycles!

 

crutschow
ok thank you i will change the comparator to increase the % dutycycles!

Do you mean change to a circuit using comparators?

Below is an example circuit for that:

 

Hello im actually on another project i will response you as soon as possible!
thank you!

 

crutschow

Hello i have tried this way for a clock in of 195hz on pin 2 monostable mode! i have still no pwm out put here is my schematic

 

crutschow

Hello i have tried this way for a clock in of 195hz on pin 2 monostable mode! i have still no pwm out put here is my schematic

Since you randomly seem to be changing the circuit and not following what I have said, I have no further comments.

 

why? ive tried with your drawing post 40 and its the same result maybe my 555 is wrong! i was trying to have an external clock! and see if it vary! sorry for disturbs

 

ive tried with your drawing post 40 and its the same result maybe my 555 is wrong!

Most likely you have an error in your wiring or part's value.

i was trying to have an external clock!

Where did you get a clock frequency of 195Hz?
My simulation shows a clock frequency of ≈1.38KHz.

And why does your circuit have a 1k resistor and 10nF cap at the 741 output when mine doesn't?
As I previously mentioned, a capacitor at the 741 output can cause oscillations.

If you can't carefully follow what I say or what is on a schematic, then I'm spinning my wheels here.

 

crutschow

ok (i asume a was off topic) (i am trying with a monostable pwm method!) i have tried alone and need some explanations
the clock frequency is from a 74HC4060 with 16mhz xtal and a 4017 output of 195,3hz!
now if its possible i would like to put this frequency like reference frequency on a 555 monostable pwm(if somthing wrong just tell me) the shematic post44 is an advice from one who told me to put a 10nf between pin 5 of the 555 and ground! i have done it and there was no results! what is your opinion?
regards

 

is an advice from one who told me to put a 10nf between pin 5 of the 555 and ground

That advice is if there's no other connection to pin 5.
But, if you want to heed his advice, than you don't need mine.
Take your pick.

For a 195Hz clock try changing C4 to 100nF and R3 to 20k.

 

Hello sorry for my incompetence but on post 42 what is (mode-in?)
can i put an external clock on this circuit?
thank you

 

on post 42 what is (mode-in?)

Mod_in is the modulation input that controls the PWM duty-cycle.

can i put an external clock on this circuit?

No.

 

Is there an other circuit that can hold an external clock?

 

Here is single chip solution (pot external) that includes external clock and stable V to Duty Cycle control circuit.

Takes maybe 10 - 15 lines of code.

Board to dev on $ 10. https://www.cypress.com/documentati...oc-5lp-prototyping-kit-onboard-programmer-and

IDE ( PSOC Creator) and compiler free. https://www.cypress.com/products/psoc-creator-integrated-design-environment-ide





What is external clock frequency range ? What resolution do you need duty cycle ? 16 bits enough ?
That would mean duty cycle resolution 1 part in ~ 65,000. Note system noise would probably cut
that down to something like 1 part in 10,000, or .01%

Note right hand window, resources used versus left. Most are left for doing additional tasks.



Regards, Dana.

 

danadak

ok dana look like easy to use!
thank you

 

and if i want to synchronize the lm 339 pwm with a fixed frequency is it possible?

 

In the PSOC there are also sync comparators that can be used -



The output is updated on the clock edge.

If you just want to stick with LM339 circuit use a clock sync circuit at the output of the LM339 -

http://www-inst.eecs.berkeley.edu/~cs150/sp12/agenda/lec/lec16-synch.pdf




Regards, Dana.

 

ok, thank you Dana

 

After some thought I realized the LM339 circuit could be synchronized to an external pulse.
Below is the simulation of the modified circuit with a sync input.
The free running frequency of U1 should be about 5-10% lower than the sync frequency for reliable synchronization.

To allow for component tolerances you likely would have to make R1 a pot to get the desired free run frequency.

 

@MATT838383 You may want to look into small Picmicro's, you most likeley could have achieved the result with a single 8 pin micro in less time than the posts have taken!
Max.

 

Ok crutzshow thank you for this detail (synchro input) i will try this example and give you a result soon!