working with non 5V inputs

[rahulcet]

I wrote apgm in C 18 where in i use the PIC to sense teh frequency of variation of an input which unfotunately isnt TTL compatible. I use the Timer 1 module for getting the frequency. Will I get the same results as for a 5 V input. Please do help me fast. this is for my final year project.

 

[geko]

No one can answer that question unless you tell us what signal your are presenting to the input.

A schematic would be be best, or an accurate description at least.

 

[rahulcet]

the input is a square wave.

 

[russ_hensel]

Run it thru a circuit to make it ttl. What is this circuit? Depends on what the input is.

 

[rahulcet]

dear rus the input is square wave mate. can ya suggest something to make it 5 V. how about opamps?

 

[geko]

Yes an opamp will work - if the circuit you have is the one I'm thinking of.

 

[rahulcet]

Thanls Mate

 

[russ_hensel]

dear rus the input is square wave mate. can ya suggest something to make it 5 V. how about opamps?

All square waves are not created equal.

What is the frequency, the positive and negative peak, the source impedance.

And yes an op amp might be useful, but could be either too much or not enough.

 

[be80be]

A 4N33 or 4n35 Optocoupler would work