Battery indicator that makes LED blink

[yeeshkul]

Friend of mine has some sort of a distortion that has this indication - the ON/OFF LED starts blinking when the battery goes low. Does anyone have an idea for schematics?

[GibsonGM]

Neat idea, yeesh...I think you could drop this ckt right onto a board as-is and have it do the job, if you have enough space.  You'd need to have a 2nd LED for the indicator with this one...to make the existing one blink would take a couple of more steps to achieve. 
Might have to change the voltage divider & diode (maybe a 5.1V zener?) to customize it.
It's the 6th one down on this page:

http://www.ece.uvic.ca/499/2001b/group06/schem.html

[GibsonGM]

On second thought, the same thing can be achieved really simply, with one LED that functions like a normal indicator light until the battery goes to about 7.4 volts.  I found this ckt on the web and modified it a bit so it's more useful...playing with the cap value and that threshold resistor set the level where the LED starts flashing.  Insert the ckt at the stomp switch where your typical LED would go:

[yeeshkul]

Thank you for your reply G. By the way which one of those two may have a lower current drain?
Cheers

[Paul Perry (Frostwave)]

Thanks for that GibsonGM!
that zener is a 4.7V 0.5W if anyone is wondering.

[kusi]

hi,

here is a alternative circuit with a Schmitt-Trigger! This circuit is used in the ARTEC-Pedals.



(the toshiba 4S584F is a SMD-Device!)

regards,
kusi

[yeeshkul]

what is the diode in this one? Zener 4.3V?

[joelap]

What places sell that Toshiba IC?  Would any Schmitt trigger work?

EDIT: datasheet for the toshiba found if anyone's interested.

http://www.toshiba.com/taec/components2/Datasheet_Sync//164/7400.pdf

[GibsonGM]

No prob, Yeesh.  This is actually a neat concept...I realized after I'd posted that the LED in my 2 tranny post will only flash when the batt. is low, and doesn't stay ON, and THEN flash when things run down!  So we need to come up with something that's normally HIGH, and then goes LOW with a voltage of maybe 7.5V.  More complicated that it seemed at first, lol.  Something to do with using the transistor(s) to source the current, maybe.  I wonder how Kusi's ckt operates?
I'd like to use this one myself, so I'll see if I can find anything else out there on the net and post it if I do!