Timed delayed door alarm - refrigerator

Projects General Guidance
1

I'm trying to develop a time delay alarm unit, like those used on refrigerators when the door is left opened. My skill level is novice. I want it to be self-contained (battery) with a low battery led using a reed switch. The sound is important. It can just be a noisy piezo but needs to be an nice (but insistent beep). Attached is a rough approach that I'd like to refine to a nice small unit. It might make sense to alter an existing alarm (see attached wireless sensor - maybe replace the wireless aspect with a speaker). Couple of questions.

  1. Overall are there any suggested improvements to the design for streamlining so that the starting point is stronger (maybe using a microprocessor)?
  2. What design changes to incorporate the beeping sound I'm looking for? Presumably I'd want the ability to adjust the input to vary the sound. And the speaker needs to be compact.
  3. Any thoughts on modifying an off the shelf product such as a jasco GE 45132?
  4. Does anyone know an electronics-fabrication guy in the Raleigh-Chapel Hill, NC area who could assist?

Example Embodiment - Schematic (7-11-2010).jpg
Example Embodiment - Schematic (7-11-2010).jpg1700×2200 213 KB

45131webd2.jpg

2

Arduino, or the Mini or Nano variants certainly could do this.

A microcomputer gives you flexibility to do things like have the audible alarm change over time, becoming more insistent, then snoozing for a few minutes if no response, etc.

If you're interested in ideas like this in the long run, then learn Arduino.

Around RTP, try these guys: http://groups.google.com/group/trianglearduino