Adjustable frequency and duty cycle circuit .

[arg733]

Hi
I need an easy schematic for a pulse generator that i can adjust duty cycle ( 0% - 100% ) and frequency (1hz - 100khz or more) INDEPENDENTLY

I tried several circuits using 555s but duty cycle was affecting frequency and vice-versa and i could not get it to 0% and 100% duty. I tried everything i could thing of, i don't know what else to do.

 

[jackorocko]

You do realize that a 0% and 100% duty cycle is equivalent to 0Hz?

 

[Harald Kapp]

jackorocko,
you're right, of course, but that doesn't help, does it?

Here is a description: http://www.edn.com/article/480947-Circuit_produces_variable_frequency_duty_cycle.php
By the way: 0% and 100 % are ecluded explicitely, too.
Unfortunately, the linked PDF and figures do not exist (at least I get an error message).

An interesting circuit could be this: http://pdfserv.maxim-ic.com/en/ds/MAX038.pdf
but it is limited to 15 % ... 85 % duty cycle.

Another rather simple circuit is here: http://www.rmcybernetics.com/projects/DIY_Devices/homemade_signal_generator2.htm

Google's your friend


Harald

 

[jackorocko]

you're right, of course, but that doesn't help, does it?

No, but I am questioning why one needs a 0% to 100% duty cycle when they specify the need for a 1hz - 100khz freq. I guess what I was hinting at is are you sure you need 0% to 100% functionality and to what limits he could get away with? Didn't really see my post being that bad, but ok

 

[arg733]

Thanks

Thanks for the quick reply.
My original idea was to have a pot and trim it down to 0% (cutoff) but I can have a switch for this. So yes you are right, 0% and 100% is 0hz .
I should be ok with 15%-85%
Thank you very much.