I like your version better, Steve! Attaboy!


At 11:09 PM 5/25/2003 +0100, you wrote:
>Try this or a deviant of it should work
>
>------+---E  PNP  C--------+--(vcc)
>       |---R---B            |
>                   |                |
>                   |               cap electrolitic (100Us hold up time min)
>                   R            |
>                   |           (gnd)
>                   +-----RA3 (open drain)
>                   |
>                  push button
>                   |
>                   |
>--------------+--------------(gnd)
>
>Operation as follows
>1 push button closed makes unit start
>2 make ra3 output and low
>3 change RA3 to input and check for 0v (once every 100mS for a short
>time(2us))
>4 read port if zero for two of three checks then
>5 prepare to power down
>6 do save
>7 RA3 input
>
>Circuit can also auto power down if u want it to
>
>Steve...
>
>
>-----Original Message-----
>From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU] On
>Behalf Of Tony Harris
>Sent: 25 May 2003 20:53
>To: PICLIST@MITVMA.MIT.EDU
>Subject: [EE]: Good soft on/off switch circuit??
>
>
>Hi all,
>
>I need to find a decent circuit to do a soft on/off.
>
>Basically, if turned on, I want my pic to boot up.
>
>If turned off, I want a second where it is still on so that I can store some
>data to eprom before being powered down.
>
>I'm thinking of using a no momentary pushbutton to control the system.
>
>My only other option is to use a regular switch and a large cap where if a
>given pin goes low, store the data to eprom, I'd rather the soft on/off
>switch if possible.
>
>Plus, I really don't want any power drawn in the off state - I'm just not
>sure how to do this.
>
>For those that are curious - no this isn't for any kind of school project,
>or for work - this is for my own knowledge and an experiment I'm doing.
>
>-Tony
>
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