What's the application this has a bearing on how / what and how fast you need to sense S -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Anand Dhuru Sent: 06 January 2007 08:14 To: Microcontroller discussion list - Public. Subject: Re: [PIC]: Phase failure detection Just as I suspected :( Andre's suggestion would be fine to check basic health of the phases, but would not indicate a wrong sequence, and/or would also get fooled by a phase signal 'manifesting' itself on another weak / dead phase. I recollect Russel had explained this phenomenon in some detail a while back. In which case, would not my original concept as described in the first post be the best approach? Or are there pitfalls here too? Regards, Anand ----- Original Message ----- From: "Steve Smith" To: "'Microcontroller discussion list - Public.'" Sent: Saturday, January 06, 2007 1:06 PM Subject: RE: [PIC]: Phase failure detection > Ahh but just checking the period doesn't reveal the direction of rotation > only that by comparison they are all there. > > There is another complication caused by the real world if the supply is > taken via a delta / star transformer and a motor is connected to the > secondary you are monitoring, a failure in the primary supply will not > change the period only the voltage (of two phases)as the motor will > continue > to run and help reinstate the third phase. > > It maybe necessary to monitor the voltage using a voltage sensing > arrangement depending upon application. You have to do this in a UPS to > ensure correct operation of the static switch under failure conditions. > > Regards Steve > > -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf > Of > Andre Abelian > Sent: 05 January 2007 18:07 > To: Microcontroller discussion list - Public. > Subject: RE: [PIC]: Phase failure detection > > Anand, > > if you compare together they may not be the same and > you will end up an error. This is what I would do. > connect all 3 phases thru optoisolater and mux connect > to pic CCP input and capture the speed. > > 1. select first phase capture and save it > 2. do same thing on all other 2 > > now you have 3 variables that you can decide what to do > with them. they may or may not be exact same values but > will be very close. > > Andre Abelian > > > > -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf > Of Anand Dhuru > Sent: Friday, January 05, 2007 8:32 AM > To: Piclist > Subject: [PIC]: Phase failure detection > > > > > Hi folks, > > I am building a circuit that needs to monitor the 3 phases in the mains, > and > > detect if (a) any one phase fails, and (b) if the phases are connected > improperly. > > After some search I found > http://www.picbasic.org/forum/archiv...hp/t-2134.html to be pretty close > to > what I need. > > What would be the best way to go about it? > > Would this logic work? > > Detect positive edge on phase 1 > Start Timer 0 > Detect positive edge on phase 2 > Read Timer 0 as variable 1 > Detect positive edge on phase 3 > Read Timer 0 as variable 2 > Stop + Reset timer > If Variable 1 is equal to (almost) = (Variable 2)/2 = 6.67 ms (for 50 hz) > then all is ok. > > Start again. > > Am I on the right track, or is there a better/easier way to do this? > > Regards, > > Anand > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.432 / Virus Database: 268.16.5/616 - Release Date: 04-Jan-07 > 1:34 PM > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist