Student Circuit Help! LED flasher/Countdown Circuit.

[Wintermute42]

Hi everyone,

I am building a indicator system at the moment to cause an LED to flash whenever someone removes a box from its position. The box sits upon a switch and when removed, completes the circuit and powers up the LED flasher, which will stay flashing even if the box is replaced until someone presses the reset button. I've got this stage working so far using the following circuit: http://i.imgur.com/yha9rgY.png.

However I would also like to add a Countdown so that the LED flasher would also be activated if the reset switch has not been pressed for a set amount of time (say 10 mins) using a microcontroller. My thoughts are that the microcontroller would be programmed to simply count down from 10 mins as soon as it is powered (whenever the circuit is not broken by the second switch) and then set off the LED after the time is up, until the reset switch is pressed.

This way the LED will flash in the following cases:
1- The Box is removed. (Turned off by Reset Switch)
2- The reset switch has not been pressed for 10 minutes (Turned off by reset switch)

I'm relatively newbish at this sort of thing, so any help at all (especially in the form of circuit diagrams) would be extremely appreciated! (Also no need to worry about the microcontroller programming in this case).

Thanks guys!

[pebe]

The micro would be the best solution. Can you do the programming?

[Poline]

When I was a student and planned to work at an electronic engineering company I used google and wikipedia to study circuit diagrams. It's difficult to help distantly, but the best way out is to use the SE.