low voltage led for 3V coin cell

[tbender54]

I made a simple timing device with Picaxe 20M2 that operates off 3V coin cell. I want to have a red or yellow led come on when voltage drops below approx 2.5V.
It looks like I need a regulated supply to do this with Picaxe and thats out of the question.
Is there any way to do this with a few external components - does not have to be super precise.Space is limited in the device.

 

[(*steve*)]

There are voltage detector chips that will do this sort of thing. The only concern is that you're getting close to the forward voltage drop for a red LED, so it may not stay on for much longer if the voltage drops.

Something like this may do the job. (note the outputs vary and I have not verified that this will drive a LED, it's just a suggestion for a class of devices.)

 

[tbender54]

Thanks much.

Thanks I'll give them a try - certainly cheap enough!

 

[(*steve*)]

Just make sure that you get one that can either source or sink current when the voltage drops below the set point. Some can only do this when the voltage rises.

Like I said -- I didn't check.