From PICLIST@MITVMA.MIT.EDU Fri Nov 15 11:05:29 2002 Received: from cherry.ease.lsoft.com [209.119.0.109] by dpmail10.doteasy.com with ESMTP (SMTPD32-7.13) id A579B0170; Fri, 15 Nov 2002 11:05:29 -0800 Received: from PEAR.EASE.LSOFT.COM (209.119.0.19) by cherry.ease.lsoft.com (LSMTP for Digital Unix v1.1b) with SMTP id <19.007DD184@cherry.ease.lsoft.com>; Fri, 15 Nov 2002 13:51:18 -0500 Received: from MITVMA.MIT.EDU by MITVMA.MIT.EDU (LISTSERV-TCP/IP release 1.8d) with spool id 7298 for PICLIST@MITVMA.MIT.EDU; Fri, 15 Nov 2002 13:51:13 -0500 Received: from MITVMA (NJE origin SMTP@MITVMA) by MITVMA.MIT.EDU (LMail V1.2d/1.8d) with BSMTP id 7754; Fri, 15 Nov 2002 13:49:15 -0500 Received: from pop017.verizon.net [206.46.170.210] by mitvma.mit.edu (IBM VM SMTP Level 320) via TCP with SMTP ; Fri, 15 Nov 2002 13:49:15 EST X-Comment: mitvma.mit.edu: Mail was sent by pop017.verizon.net Received: from djm ([151.199.100.101]) by pop017.verizon.net (InterMail vM.5.01.05.09 201-253-122-126-109-20020611) with ESMTP id <20021115184914.HUXF1423.pop017.verizon.net@djm> for ; Fri, 15 Nov 2002 12:49:14 -0600 References: <004b01c28c23$51b8ba40$6501a8c0@potshe01.pa.comcast.net> <006401c28ca1$b0a4aa40$6501a8c0@potshe01.pa.comcast.net> <009101c28caa$1eec0b30$0300a8c0@main> <007701c28cb1$6e1eaf80$6501a8c0@potshe01.pa.comcast.net> <001f01c28cb7$5f128bf0$0300a8c0@main> <00d201c28cbc$38655320$6501a8c0@potshe01.pa.comcast.net> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 X-Authentication-Info: Submitted using SMTP AUTH LOGIN at pop017.verizon.net from [151.199.100.101] at Fri, 15 Nov 2002 12:49:14 -0600 Message-ID: <003301c28cd7$b3344640$0a01a8c0@djm> Date: Fri, 15 Nov 2002 13:49:15 -0500 Reply-To: pic microcontroller discussion list Sender: pic microcontroller discussion list From: "Dennis J. Murray" Subject: Re: [PIC]: 16F627 brown out? question To: PICLIST@MITVMA.MIT.EDU X-RCPT-TO: Status: R X-UIDL: 277600713 X-Evolution-Source: pop://mailinglist%40farcite.net@mail.farcite.net/ X-Evolution: 00000793-0000 If I can offer my 2 cents worth (you get what you pay for)! I also ran into problems with a very low power PIC running @ 32KHz. that included short power supply shutdowns. In my case, part of the problem was the bypass cap across the chip (0.1 uf) held the chip running a split second longer than desired. Once that was resolved, I put the debugged chip in the final circuit and it wouldn't shut down at all on it's own, even WITH the battery disconnected! Turned out the PIC was getting enough power from the camera whose electronic shutter the PIC was trying to trip! Once the battery was removed, the PIC got its power thru the internal protection diode of the PIC's output port I was driving the camera with - and that was enough to keep the PIC running. (I know, Microchip has documented this as something to be careful with, but I missed it!) This is probably not your problem, just thought it may help. Good luck! Dennis ----- Original Message ----- From: "Scott Touchton" To: Sent: Friday, November 15, 2002 10:32 AM Subject: Re: [PIC]: 16F627 brown out? question > > As an experiment, try making the 300mS time much larger so that the > > processor is held at 0V power longer > > There be the other aspect of the problem. I have had about 50 of these fail > in the field. I have not been able to duplicate the problem in my lab. The > customer removes the battery, thus clearing the problem. This probably > means you are right... receiver was at 0V much longer than 300mS. I could > change the timing and put a bunch in the field to see what happens. > > I have one on my bench that got returned with the battery in it. Managed to > remove it from its case without disturbing power so I can make observations > and try some things. > > I like your suggestion, just can't duplicate the problem to test. I know if > I power down the on my bench it will power back up just fine (at least with > my luck it will). > > I have tried temperature and battery voltage variation to duplicate the > issue with no luck. > > > > crystal oscillator takes a while (1000 cycles if I remember right) before > > the chip is allowed to run. This is independent of the powerup timer, and > > would be over 30mS in your case. > > So that means the oscillator should be stabilized before the program is > released, right? > > > The 16F627 should draw under 10uA with a 32KHz crystal. Is it really > > worth it to shut down the processor completely for such short periods of > > time? > > Nope... total waste to power it down. This is all going away in my > redesign. I don't know why the engineer before me did it this way. > > > > > ***************************************************************** > > Embed Inc, embedded system specialists in Littleton Massachusetts > > (978) 742-9014, http://www.embedinc.com > > > > -- > > http://www.piclist.com hint: The PICList is archived three different > > ways. See http://www.piclist.com/#archives for details. > > > > > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.