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Vref doubt

 
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xxopiumxx



Joined: 01 Jul 2011
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Vref doubt
PostPosted: Fri Nov 30, 2012 7:38 am     Reply with quote

Regards,

I'm trying to read the frequency of a chain pulses with the CCP module.
The problem is that the max voltage of the pulse is 2.5v. Is there any way in which I could change the reference voltage of the comparator?

And, in another way, if I use the timer 3 -for example- to do the same reading the chain as external pulses, can I change the reference voltage in which the timer 'sees' the pulse?

Thanks for advance.
Mike Walne



Joined: 19 Feb 2004
Posts: 1785
Location: Boston Spa UK

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PostPosted: Fri Nov 30, 2012 7:58 am     Reply with quote

Probably.

But, you need to tell us more:-

1) PIC.
2) Compiler.
3 etc

Mike
xxopiumxx



Joined: 01 Jul 2011
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PostPosted: Fri Nov 30, 2012 8:47 am     Reply with quote

pic: pic18f2550
comp: pcwhd 4.084

thanks ^^
Gabriel



Joined: 03 Aug 2009
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PostPosted: Fri Nov 30, 2012 8:49 am     Reply with quote

Can't you amplify the signal? op amp? transistor? add a DC bias?

You say comparator but mention CCP (capture/compare/PWM).
Did you mean Schmitt trigger input level? Which one is it?

g
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CCS PCM 5.078 & CCS PCH 5.093
Mike Walne



Joined: 19 Feb 2004
Posts: 1785
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PostPosted: Tue Dec 04, 2012 5:47 am     Reply with quote

The PIC18F2550 has an analogue comparator module.

Use that to convert your 2.5V signal to a 5V signal.
Then feed comparator output to the CCP module.

Mike
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