Post by thread:Zero crossing detection circuit.

Bruce, What you want to do is run the pseudo sine wave into the input of a comparator. Ground the inverting input and feed the signal to the non-inverting input. The output will be a 0 to Vdd square wave of the same frequency. If you use a single supply rail-to-rail type you should be in business. You could also use an op amp connected as a comparator if you can't get your hands on a 'real' comparator. If using a PIC, you can use the signal to bump TMR0, or you can use the edge to produce an interrupt. Hope this helps. Fr. Tom McGahee ---------- > From: Bruce Turrentine <spam_OUTTurrbieTakeThisOuTAOL.COM> > To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU > Subject: Zero crossing dection circuit. > Date: Thursday, June 25, 1998 10:40 AM > > I am working on an automotive timing circuit that uses a toyota reluctor pick > up. It's output is a pseudo sine wave that changes in frequency and amplitude > as the rpm changes. The ideal point to in the wave to send a position > interrupt is as the wave passes zero. I've tried running it through an op amp, > letting the wave swing from a 5v pedestal, and computing the midpoint between > the two peaks but this eats up too much time is an "after the event has come > and gone" solution. Anybody have a suggestion? > > Bruce