Delay a pulses freq. by x% (5v, 50%, variable frequency)

[[email protected]]

Hello,

I'm looking for advise on how to delay a pulse that may vary in
frequency.
Would like to delay its frequency by a specific percentage (ideally
adjustable delay percent).

Are there any simple circuit schematics I could follow to do this ?

I'm looking for a simple, cheap, and small way to do this.

Thanks for any help!

 

[[email protected]]

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Delay it with respect to what?
---


---
You can the increase the pulse frequency, and you can lower it, but you
can't "delay it" without respect to a certain instant in time.

Are you perhaps looking for a way to vary the width of the pulse as its
frequency varies?
---


---
Maybe, if you can describe what you want, or your application,
accurately.

JF

Hi John,

Sorry for the lack of details here.

Delay it in respect to the original frequency.
Basically, decrease the frequency by a given percent.

Basically, if I have a pulse train at 500Hz, I would like to be able
to change that by, say, 10%, so the output would then be 450Hz.

And, as the frequency of that pulse train changes coming into the
circuit, it would always output 10% lower than the incoming frequency.

I hope that explains it a little better.

Thanks!

 

[[email protected]]

I assume that the "50" in the subject line refers to the duty cycle of
the input and output; if so, how close does the output have to be to
50%?

BTW, what you want to do is called "frequency translation" or "frequency
shifting", not pulse delay.

Anyway, for a 50% duty cycle in and a 10% translation down, input here's
one way to do it:

1. Use an up-counter to continuously determine the half-periods of the
  incoming signal.

2. As each edge comes in, store the accumulated count in a register
 (let's call it CNT1) and reset the counter so it'll start counting
  again from zero.

3. Divide the contents of CNT1 by ten, add that number to CNT1 and store
  the sum in CNT2.

4. Load a down-counter with the contents of CNT2 and have it count down
  using the same clock as the up-counter.  When it gets to zero have it
  toggle a "D" type flip-flop and reload itself with the contents of
  CNT2

That way CNT1 will refresh itself on its own terms, as will CNT2, the
down-counter will generate half cycles which will be 10% longer than the
input's and the flip-flop will automatically assemble a square wave
which will be 10% lower in frequency than the input signal.  

---

Even simpler:

Vin>--+---------A  _
      |      EXNOR Y--[R]--+--[Y = MX + B]--+--[VCO]--+-->Vout
      +--[R]-+--B          |                |         |
             |             |                |         |
            [C]           [C]               |         |
             |             |                |         |
GND>---------+-------------+----------------+---------+-->GND

JF

Hi John,

Thanks again for your continued assistance.

Would it be possible for you to post the components you recommend to
do this with the least amount of parts ?

I'm looking to build this in a small footprint (small as practical).
(I am more familiar with analog components than digital.)

 

[[email protected]]

Hi John,

Thanks again.
And sorry for not supplying all the info you need.

Input freq range would be from 0-1500Hz.
The output should be from 0-20% less than input freq.
Resolution, accuracy, and in/out fidelity should be as good as
possible/realistic.
Ideally, the out would be the same as in, except just the change in
freq.

For the smallest footprint, you need to abandon your dependency on
analog and go digital.

Agreed, that is why I am here picking your brain for help

Thanks!

 

[neon]

0- to 1500hz WHAT ARE TALKING ABOUT zero frequency is a short ,dc whatever but not a frequency ever. LM555 can do all of this pluss more look it up. and it is very cheap and gubs of info on it.

 

[[email protected]]

Hi John,
Sorry for the delay in replying to your post.
I'll try below...

The frequency will come from a rotating wheel generating the pulses.
The wheel will vary in speed from stopped (=0) to higher speeds
(=1500).
I guess the circuit somehow needs to be able to handle this.

The output should be from 0-20% less than input freq.

In this case, perhaps the circuit just stops pulses on the output.
Same as the input.
No pulses in, no pulses out.

---
I don't know what that means; you're the one who has to write the spec.

10%? 1%? $1000?, $10?
---

Well, basically as good as possible while ralistic.

Ex:
10% = 5 parts and $30
But
1% = 30 parts and $180

Then I'll take 10%

But,for example if the difference between 10% and 1% is just a matter
of higher tolerance parts and minimal price difference, then I would
go for the 1% design (or less %)

Yes, it would be 50% duty cycle.



Thanks John!
Sorry again for trying your patience with the lack of info you need.