??? 12/04/05 19:01 Read: times |
#104668 - Extreme care?? Responding to: ???'s previous message |
Erik said:
If you feed the comparator, say, 220V with a resistor and a zener, you can get excellent zero crossing detection with very little noise suspectibility. Very nice, Erik. But remember, we want to have galvanic isolation to mains, we want to detect zero crossings of both polarities and we want to make the job with a very low unipolar supply voltage (+3.0V). How looks your recommendation now? You can, of course, make something work with a small hystersis if you take extreme care in layout Again, a hysteresis of 20mV is no problem, if you use proper ground routing and filtering. Requirements and efforts are less than getting an 8bit ADC to work, which shows a LSB of about 20mV. And for this job "extreme care" isn't needed either. Kai |