Small timer 'project'

I hope someone can help me with this project.

I need a very small switch device, no bigger than about 15 mm in diameter and up to say 25 mm thick, and powered by a small watch battery. The device would have one main function - when you press the switch, a light (say LED) flashes, at say 1 to 2 sec intervals for around 30 mins, then goes off. That's it. It would also be nice if it had a battery low function so that the LED would say flicker continuously for say 15 seconds if the battery was below a certain useable level.

Many thanks


Reply to
Barry Gower
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The circuit it's self is rather simple. The first requirement can be done with a 556 chip. The hardest part is your size requirement. Can you work with SMT?


Reply to
Tom Biasi

As Tom said: Surface-Mount Technology.

Selecting a part that reduces the size of *that* will be your biggest packaging problem.

What else would it possibly be?

The first thing you do when learning how to use a microcontroller is to get it to flash a LED. This one-chip solution fits your size requirements well. Enough said?

A battery-low indicator that uses up yet more battery power is so counter-intuitive. A microcontroller could use its onboard A/D converter to do this, however.

Isn't there a high school or community college full of nerds somewhere near you?

Reply to

Or learn to "roll your own"

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Reply to

there's plenty of small SMD switches out there.

?? 100% natural

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Reply to
Jasen Betts

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