Modifying an Alarm Clock Using Mosfets

[menimitz]

I wasn't sure whether to ask this here or on another part of the forum, but this feels like a beginner's issue so here it goes.

I have an alarm clock that I would like to modify so I can control it with a micro-controller.  I eventually want to build my own alarm clock for this project, but don't have time at the moment to do that. 

I want to be able to switch the alarm mode on and off using the uC.  Below is a rough diagram of what I believe the switch does after cracking it open: 

(I can't seem to figure out how to post an image so...)
                     
             Sliding Switch 
                          ______  ON
Vdd_________/
                          ______ OFF


ON and OFF run under the 7-Segment Display to what I assume is a uC. 


How can I replace this switch with a transistor setup? 

I couldn't find common inside the clock, and most of the main pcb is covered by the 7-segment display which is held down with sonic welds I don't want to break. 

Any thoughts on how to switch this would be greatly appreciated.  I don't have any experience with mosfets but would like to use them more just to get acquainted with their use. 

Thanks for any advice here.

[PA0PBZ]

You can probably just switch it with a digital output of a uC, it's likely just a 1/0 input.
Can you see what kind of chip is in there? Maybe find a datasheet and see how the alarm is switched on and off.

If that is a dead end you can measure what the switch does (you have a DMM I hope), and if it looks like weird signals or voltages you can always use an analog cmos switch.

[menimitz]

I do have both a DMM and an old Tek scope I just didn't have a chance to take any real measurements yet. I guess my real question here is how do you switch a load using a fet in that configuration. I only know how to use them with the source connected to ground. Is it possible to use one in that crude circuit above.

This has really turned academic at this point because I think I may scrap the project in its current form anyway.