How measure frequency of signals other than squarewaves with timer capture?

J

jmur

New Member

• Apr 24, 2010

• #1

Im using timer capture on an lpc2106 to measure frequency of signals by basically counting the number of rising edges captured in 1 second. This works fine for squarewaves but not for any other signal types.
Is there way to measure the frequency of other wave types with timer capture?

Regards,
J

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Apr 24, 2010

• #2

Simply square the wave before you apply it to the chip.

 

J

jmur

New Member

• Apr 24, 2010

• #3

*Sounds* easy, I would need a circuit though that can output a square for a square, triangle, rampup or rampdown input, is this possible what kind of circuit would you suggest? maybe a comparator would do the job?
Regards,
J

 

Last edited: Apr 24, 2010

Nigel Goodwin

Super Moderator

Most Helpful Member

• Apr 24, 2010

• #4

Exactly, a compartor - or just an over driven amplifier. How do you think frequency counters work?.

 

Smartie

Member

• Apr 24, 2010

• #5

Maybe a voltage comparator?

 

U

upand_at_them

Active Member

• Apr 24, 2010

• #6

Zero-crossing detector?

 

J

jmur

New Member

• Apr 24, 2010

• #7

I used a lm358 as a noninverting comparator with vref set at 50% of the input vpp, works fine.
Regards,
j