Building something from a concept (was: Need device suggestions)

[JeffM]

I need a remotely controlled

A cast-off TV remote
and an infrared detector / integrator triggering a flip-flop.

count-down timer (5 minutes)

That's 300 seconds.

that will light one LED with 30 seconds remaining

That's 270 seconds--9 parts out of 10.

and another when there is no more time left.

That's 10 parts out of 10--the last output of a CD4017.
The previous state was the 9th output of the decade counter.

To get the 30-second clock, use a chip with a binary divider chain
and an integral oscillator (CD4060).
Tweak this.
http://groups.google.com/group/sci.electronics.basics/msg/eb8d28562c582bb4?dmode=source

Ideally, it would:
4)[...]the first led would blink once per second for 30 seconds

AND the output of the 4017 with one of the lower-count pins of the
4060.

2) be compact enough to be unobtrusive on a podium or table top.

Essentially 4 chips and 2 LEDs. The battery is the biggest single
part.
The chip count goes down to 1 if you use a microcontroller.

and then both lights would glow steadily until reset by the instructor.

One more section of the AND gate chip.

Before you start any of this, you need to find a flesh & blood person
who has previously held the proper end of a solder iron.

 

[JeffM]

The soldering is the part I -can- handle ;-)

Actually, *solder[ing] iron* was a metaphor.

The rest of your response sounds incredibly intelligent
... but well beyond my experience / training.

Exactly my point: **Ideas** are a dime a dozen.

You need someone who
1) understands the concepts.
2) can translate them into hardware
3) is THERE to troubleshoot it when it doesn't work the 1st time

When I was a kid (several decades ago), I would have just trundled off
to the nearest electronics component store with the shopping list and
started piecing things together.

There are still some left where I am
--but today you don't even need to leave your keyboard.
http://www.digikey.com/
http://www.mouser.com/

I am probably reduced to cannibalizing toys and egg timers.

A *microcontroller* is the way these things are done nowadays.
Almost everything is done in software
(and when it needs to be altered, often you just tweak the code).
See if you can't find a local guy who does that.
Got a community college or high school nearby?
Maybe barter with him for something within your skill set.
Maybe he'll teach you a few of the tricks to boot.
..
..
WRT your posting style: NOT *3* hyphens.
http://groups.google.com/group/rec....phens.and-a-space+Like.so+automatically-*-*-*
http://groups.google.com/group/alt....60e24?q=2-hyphens-and-a-space+*-automatically