I'm working on a project where there will be an RF receiver running continuously and powered by a battery. To extend battery life I want to power the receiver with a timer, so the receiver will be powered for perhaps .25 seconds. If the receiver catches a signal then the receiver will remain powered until the signal is gone, but if it does not catch a signal then it will power off for .75 seconds. Can someone point me to a timer circuit that uses all off-the-shelf parts that will fill this need? I'm hoping to avoid the complexity of adding a processor and writing code and I'm hoping there are some off the shelf parts that can accomplish this. Thanks in advance!

 

Take a look at TimerBlox by Linear Technology.

Failing that, a CMOS 555 could be used, albeit with external components. Look for Bill Marsden's 555 blog here for ideas.

The term for what you are looking for is a retriggerable one-shot / missing pulse detector i.e. the timing is reset on any trigger. When the triggers stop it times out.

I'm hoping to avoid the complexity of adding a processor and writing code and I'm hoping there are some off the shelf parts that can accomplish this.

I don't know, this could be done in a jiffy with a 10F/12F PIC (if you are tooled up for it). Sleep the processor. Wake up on input change and start timer. Reset timer each input change. If the timer runs out, arm it for wakeup on change again and then sleep it.

 

my Yeasu radios do this already.