-----Original Message----- From: Ricardo Seixas To: PICLIST@MITVMA.MIT.EDU Date: Wednesday, 15 October 1997 5:35 Subject: Sensing Low Battery Condition (Thanks!!) > > > I'd like to thanks all that replyed to my question. > In this circuit I'll use the method described by Mike Smith >to store "battery used time" since I'm using nicad. > Using one or two EEPROM locations I can create a counter that >increment every minute and, when a determined count (time) is reached >I can display a message with a safety margin to recycle the battery. > When the battery is recharged I can press a button before turn-on >the device then, at power-up the start routine check the button and if >pressed reset the counter. > Another thing that flashed my mind is to use the EEPROM counter as a >safety device so, when a preset used time (or number of power-up's)is >reached the user at the next power-up MUST press a pre-determined sequence >in the buttons, otherwise the device becomes useless. > To increment the counter on EEPROM every minute is no problem since >1x10^6 cycles (EEPROM safety margin) = 694 days, 24 hours a day and, the >circuit is used 2 or 3 times a day (one hour max.). > Note, this is note a comercial device. > Now, another question ... > > Do nicads self-discharge when not in use ? > If yes Then > this method becomes half useless > End If > Loop > Yes, somewhat, but the specs sheets should give you enough data to include this effect. Use a sleep system / RTC to keep track of time. MikeS