Long Duration Timer

[Hello]

I need a timer circuit building block to incorporate into a device I am building. It needs to provide a delay of at least 15 minutes, draw as little current as possible, especially when "off", operate from 12v DC (with delay duration largely independent of small supply flutuations), and have an input trigger that becomes inactive once the delay is started (unlike the 555).
The CD4047 fits the bill nicely, except for the delay obtainable directly. I have considered coupling it to a counter chip. Also, I have considered the EXAR family of chips, but they appear to have become dated or discontinued and somewhat unavailable (and also relatively expensive per single unit).
I would appreciate hearing what some of you folks have done and ideas you have in this regard. Thank you!

[Tweetldee]

You need to give more information about your requirements. Stuff like:
What does the trigger look like? Is it a pulse? what is the polarity? Voltage levels? Does the delay trigger on rising edge or falling edge?
What is the maximum current the delay block is allowed to draw?
What does the output of the delay block look like? Voltage level? Polarity? Current source or sink? Current levels?
Define the "off" condition.<p>If you can define these parameters, then mayne someone can help you with your circuit.<p>Dave M

[Chris Smith]

The 555, 556, or 558 should do the trick. One is a single 555, the other is a dual 555, the third is a quad 555.

[n7hqk]

Stuff a PIC in the circuit... A simple timing loop will allow you to delay from millisecs to months! one of the 8 pin flash versions like the 12F629 is around $1 in low quanities and needs only a power supply & filter cap for external parts. Check out www.melabs.com for a slick programming package...<p>Good Luck!