PIC backup power supply: switchover ???

[xnihilo]

My method for the backup is 'simple'-ish. Used it a number of times, works for me...
+5v normally powers the whole circuit except for the PIC. It also trickle charges a 3 cell pack of NiMH batt's thru a blocking diode and a current limiting resistor (I also have a jumper that adds another resistor in parallel if I need to do a manual fast charge for awhile, i.e. I let it run too long on backup). This 3 cell pack directly feeds the PIC. I tap off the main +5v line into a normal port and keep an eye on it. If I lose the main +5v line, I shut down other peripherals, drop the clock speed, and start napping until main power comes back up. A single PIC running off 3 AAA 650 mAh NiMH cells can run a long time in sleep / low power mode. Even looping on the internal low speed clock (~37Khz) draws so little current that the thing can 'sleep' for a solid week before I have to worry about.

Skimask, the "crazy flying tiger"...
Remember I'm in a project where I use a gun and a mag for a DIY lasergame.
I have a pic in the gun and a pic in the mag. When the mag is in the gun, it gets its power from it. When player needs to switch to the next virtual mag, he removes the 'physical' mag, clicks on a switch to cycle through his virtual mags and then reinserts the mag in the gun. I need some power supply in the mag while it is out of the gun, it cannot sleep because player interacts with the pic inside the mag while it is away from the main power supply. See?

[skimask]

Skimask, the "crazy flying tiger"...

?????

I need some power supply in the mag while it is out of the gun, it cannot sleep because player interacts with the pic inside the mag while it is away from the main power supply. See?

So don't sleep! Sounds to me like the 'mag' is going to be fairly simple anyways. It'll take a LONG time to deplete a few AAA batts.

[xnihilo]

So don't sleep! Sounds to me like the 'mag' is going to be fairly simple anyways. It'll take a LONG time to deplete a few AAA batts.

->Who is talking about depleting batteries? It is only for a short time (while the mag is pulled out and reinserted a few seconds later) and during this time, the PIC in the mag has to continue running.
Let me explain, when I'm talking about BACKUP it is not like the one for the CMOS in a PC.
I need to switch temporarily from a supply from the GUN (good battery with a voltage regulator) to another one (3 mini batteries onboard the mag).
The mag still needs to run when I remove it from the gun unit. I want to use small wristwatch batteries to supply power to the mag while it is out of the mag.
Do you understand?

By the way, mag is not simple at all, the managment of this little ******* fills all the 1048 words of the PIC...

[skimask]

->Who is talking about depleting batteries? It is only for a short time (while the mag is pulled out and reinserted a few seconds later) and during this time, the PIC in the mag has to continue running................
By the way, mag is not simple at all, the managment of this little ******* fills all the 1048 words of the PIC...

Yes, I get it... And again, how much power do you think a PIC uses just sitting there? Just use the blocking diode and those watch batteries. It'll take awhile to drain those out and if you're careful, it could take QUITE AWHILE to drain them out.

And as far as how simple the 'mag' is...it doesn't matter if the PIC is empty or full, it's still going to draw the same current. It's sounds fairly simple to me...
Either the mag really is just that simple, or you're making it entirely too complicated.
But then again, I'm not trying to zap or fry anybody either...