Greetings colleagues. I would like help with the design of an oscillator with a variable frequency between 10 and 200 Hz and a duty cycle between 1 and 15%. I was searching but the post was already deleted because it was too old.

 

http://forum.allaboutcircuits.com/showpost.php?p=117641&postcount=6

 

Greetings colleagues. I would like help with the design of an oscillator with a variable frequency between 10 and 200 Hz and a duty cycle between 1 and 15%. I was searching but the post was already deleted because it was too old.

Was this oscillator using a 555?

 

hi ane.
Try this, Search on AAC for:
Bill Marsden's PWM circuit

E

 

Please try it from your location, at least not using vpn.

 

Was this oscillator using a 555?

It seems so, I'm not sure

 

https://forum.allaboutcircuits.com/showpost.php?p=117641&postcount=6
This is what it shows me for that page
-No input file specified-

 

This is what it says in the old post; but I don't access any.

--Actually, a 555 will do it, but not with that schematic. I've shown how to make duty cycle and frequency totally independent, it is pretty easy. See Figure 4.3 of LEDs, 555s, Flashers, and Light Chasers, it works extremely well and can do a full 100% with careful component selection.---

 

Yes

 

Now I'm browsing with the phone, but I don't think it's any different with the computer

 

the idea is to compare setpoint with triangular or saw tooth signal. then one can change the frequency of the triangular wave oscillator and since amplitude does not change, PWM output duty remains the same:

https://forum.allaboutcircuits.com/threads/bill-marsdens-pwm-circuit.44757/

of course one can can have more than one opamp or comparator available so one could replace 555 with it..

 

Greetings. Thanks for your time; but the circuit I am looking for is one that can vary the frequency and useful cycle, but after establishing the useful cycle, when the frequency varies it does not vary.

 

the idea is to compare setpoint with triangular or saw tooth signal. then one can change the frequency of the triangular wave oscillator and since amplitude does not change, PWM output duty remains the same:

https://forum.allaboutcircuits.com/threads/bill-marsdens-pwm-circuit.44757/

of course one can can have more than one opamp or comparator available so one could replace 555 with it..

I don't know why I can't see the diagram. Could you please share it if you see it. Maybe by looking at it you will understand better.

 

Greetings colleagues. I would like help with the design of an oscillator with a variable frequency between 10 and 200 Hz and a duty cycle between 1 and 15%. I was searching but the post was already deleted because it was too old.

AFAIK, posts on this forum are never deleted. Some of mine from 2006 are still here.

 

here is the image from link
R1 is used t ocontrol the frequency.
R5 is used to control duty cycle.
both controls are independent of each other.

 

Sorry if you don't understand something, I have little command of English and I use a translator most of the time. I'll show you what you show me

 

Example
https://forum.allaboutcircuits.com/blog.php?bt=682

 

here is the image from link
R1 is used t ocontrol the frequency.
R5 is used to control duty cycle.
both controls are independent of each other.

View attachment 327087

This diagram does not correspond because the useful cycle will vary as the frequency varies.

 

Look, in this link

https://forum.allaboutcircuits.com/...ycle-constant-while-changing-frequency.51975/

In comment #9 Wendy refers to the diagram, and from the title of the post and what I write I think it is the diagram that when varying the frequency in the potentiometer the useful cycle remains the same

 

Greetings. Thanks for your time; but the circuit I am looking for is one that can vary the frequency and useful cycle, but after establishing the useful cycle, when the frequency varies it does not vary.

What you want can be approximated with a single 555, but not over a 20:1 frequency range.

The circuit in #11 should do that. Here is the schematic as an image.



It also can be done without a 555, using a dual opamp (LM358) or dual comparator (LM393). You don't say if you need the circuit to run on a single supply or dual supplies. The first two schematics here cover both. Note that the second schematic can be improved.

https://www.homemade-circuits.com/op-amp-oscillator-circuits-explained/

ak