Wow, you guys rock! Thank you to everybody for the replies.
I took a trip to RadioShack to get a few supplies in order to try out Boncuk's circuit as it sounded like it used the least amount of power so far. I bought the only N-channel MOSFET that they offered, specifically the
IRF510. I built it according to the schematic and.. IT WORKED!
In practicality, I found that 10 seconds was a bit too short and that 20 seconds would be better, so I raised R1 to about 1.5mΩ (up from 470kΩ) which kept the LED lit for around 25 seconds. The capacitor discharge time takes around 30-60 seconds, which isn't a big issue.
I have a few questions:
1. The circuit would not light the 2v LED with a single 3v coin cell battery. Using two batteries (for a total of 6v), it worked fine. I am assuming that this is due to having a 2v LED and a 2v Transistor in the circuit, thus requiring a minimum of 4v. What alternatives can I use to get it down, so that I can power this circuit with a single 3v battery?
2. Why is R1 needed? Wouldn't it be the same thing if I combine R1 and R4?
3. Can I scrap R2 as R1 and R4 is already limiting the input voltage?
Now, I love Diver300's idea of using a Single gate schmitt trigger as it would eliminate two components to solder. Is anybody able to supply a Digi-Key or Mouser part number for the correct component in a
through-hole design? I'm not quite sure what I'm looking for here.
And, last question: If something like this is used, what kind of "standby" current will it use after the LED has extinguished? I'm not quite sure what this would be referred to in the data sheet.
Again, thank you to
everybody for all of the help - I couldn't be doing this without all of you and it's highly appreciated!