Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

digital pulse analysis

Status
Not open for further replies.

spyghost

New Member
hi,

i would like to ask for your suggestions on how to go about this kind of problem:

i have an external pulse that is fed into a circuit. the pulse frequency is varying, but the duty cycle is constant. the circuit simply counts the number of pulses that come.

given this kind of setup, one may simply tweak or cheat the circuit by adding more pulses, which is not favorable. this addition of pulses may be done by simply pulling a high signal low or pulling a low signal high.

if i know the rate of change of the pulses, how would i be able to determine if the next pulse that comes in the circuit is a valid pulse or not? what i am only after is checking if the pulses arrive faster than normal....

thanks!
 
spyghost said:
hi,

i would like to ask for your suggestions on how to go about this kind of problem:

i have an external pulse that is fed into a circuit. the pulse frequency is varying, but the duty cycle is constant. the circuit simply counts the number of pulses that come.

given this kind of setup, one may simply tweak or cheat the circuit by adding more pulses, which is not favorable. this addition of pulses may be done by simply pulling a high signal low or pulling a low signal high.

if i know the rate of change of the pulses, how would i be able to determine if the next pulse that comes in the circuit is a valid pulse or not? what i am only after is checking if the pulses arrive faster than normal....

thanks!

Timer setting based on known pulse frequency.

1) init timer
2) see pulse #1, start timer
3) see pulse #2, is timer expired?
YES, so pulse is legit. Goto 1
NO, so pulse is too soon(discount) Goto 1
 
Optikon: Since the frequency is varying, that is not going to work, in fact, depending on the amount of frequency variation, it may not be possible to determine when a pulse is early. Of course, there may be other factors, not given, which could be employed.
 
Russlk said:
Optikon: Since the frequency is varying, that is not going to work, in fact, depending on the amount of frequency variation, it may not be possible to determine when a pulse is early. Of course, there may be other factors, not given, which could be employed.
so, how would it work?
 
Russlk said:
Optikon: Since the frequency is varying, that is not going to work, in fact, depending on the amount of frequency variation, it may not be possible to determine when a pulse is early. Of course, there may be other factors, not given, which could be employed.

Ahh yes. You are correct, I didn't catch that. IF the freq is varying, there is no way to know unless you have some predictable method of knowing how it will vary - a relationship of some kind there..

I find it hard to believe that the frequency is truly random. There should be something that can be used for prediction.. spyghost will have to tell us what the source is, I suppose... :roll:
 
Many years ago, I worked with a "pulse time sorter" which was a servo system that used a shift register as a delay line and would track a pulse train as long as it did not change period too quickly.
 
I'm not sure I understand what you want, but it appears that you want to know if a pulse arrives earlier than normal.

If that is the case, I suggest that you start a timer (set for the minimum time between normal pulses) when a pulse arrives (or ends) and if a pulse arrives before that timer expires, then it is an extraneous one.

Len
 
ljcox said:
I'm not sure I understand what you want, but it appears that you want to know if a pulse arrives earlier than normal.

If that is the case, I suggest that you start a timer (set for the minimum time between normal pulses) when a pulse arrives (or ends) and if a pulse arrives before that timer expires, then it is an extraneous one.

Len

Well, I think the current understanding is that under "normal" conditions, the pulse frequency would vary in an unknown way. This is why I think the current conclusion is there is no way to decide whether or not a pulse is extraneous.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top