| ??? 12/04/05 14:23 Read: times |
#104662 - Mains filtering Responding to: ???'s previous message |
Russell said:
I have some basic RC filtering.. The problem with filtering is the introduce of phase shift. So, eihter only high frequency filtering can be used, with doesn't introduce relevant phase shift, or a very well known phase is introduced and subtracted by software. You are totally right, to have a clean mains signal is important when using simple zero cross detectors. And it's obvious to have a mains filter if it's not. High frequency noise can easily be removed by a simple symmetric mains pi-filter consisting of 100nF/250V~/X2 caps and 40µH/2A triac chokes, resulting in a corner frequency of about 80kHz. At secondary side of transformer connecting 2.2nF in parallel to the red LED yields additional low pass filtering showing a corner frequency of about 14kHz without introducing relevant phase shift (delay). ..and some heavy filtering in the software by using a phase & frequency locked loop to cope with mains borne interference. How do you handle this, so that wrong triggers will not block up the restauration algortihm? Kai |
