pic vs cigarettes

[Jerson]

Well described. I think the 913 has the LCD driver built in and as such is suited for this kind of application. Tray fully opened switch - thats something which might be an issue. What if you want to cheat on the timer? hehehe You could open the tray just half way and take a cigarette. I'd rather have the switch close when the tray moves out from fully closed position.

Internal clock source will be just fine for this app. See 2 hours or 2hrs 1min dont really matter when it comes to avoiding a smoke.

Why do you need interrupts? You may need to clarify this more. If this is battery powered, it makes sense to use sleep mode and an interrupt to notify the switch changeover to your program code.

1" dia, possible.

[bogdan]

At the beginning I was thinking to use external interrupts (INTE bit)…but anyway the interrupts will occur only at the END (point 6) of the cycle, when the uC will be in the sleep mode and the box was already unlocked.

So, what about if I will use a reset circuit (pull-up resistor connected to the MCLR/Vpp pin + pushbutton switch connected to ground)… will not be the same for this application?…please take a look at the pictures

[Jerson]

Definitely a good idea. However, you should consider the SLEEP command to put the PIC in ultra low power mode while counting if you power this box by a battery OR you may get just a few hours of operation.

[nomad]

that's an interesting way to quit smoking.. *cough* I'll have to try it!