Pulse Stretcher

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

How accurate?

Wow, Fairchild has the 4538 as obsolete. bummer. I've used the 4040 counter in the past to generate long pulse times. Fed by a slow running 555. Just what you wanted to hear ;)

Cheers

Sloppy. I can tune a fairly accurate master oscillator with a pot.

I'm leery of RC due to leakage. ...Jim Thompson

A low-pin-count microcontroller makes a dandy delay element, depending on the frequency of the master clock. If you have other slow functions that can be dumped into it also, it can be cost/space effective.

Use an up/down counter (7490?), count up fast during the pulse, count down slow afterward.

Or use a micro to do the same thing (if you're not making custom silicon). Is a SOT-23 package too big?

You didn't say much about your environment. If you are building a board rather than a chip, long delays are simple in software.

Assuming you want to use a counter...

Make a counter that is big enough. Load it with a magic number. After N cycles, it will overflow. Add glue around the edges to make it do what you want.

Suppose you have an active low load signal. Wire that to the pulse-out FF. Set the pulse-out with the pulse-in. Use the carry-out the top to reset the pulse-out FF. It will sit there reloading itself until you poke it again.

Maybe one of those single ripple counter ICs available (now) or umpteen years?

n ____|____ / \ | . . . | +-+-------+-+ CLK>---------------|> | +----+ | DIV n | IN>------|S Q|-+--|E TC|-+ | | | +-----------+ | +-|R | | | | +----+ +--->OUT | +-------------------------+

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

I believe that one of the new Linear Tech parts in the 'timerblox' family will do this. The one shot version goes 1uS to 34 Seconds with one resistor change. Your choice of triggering options.

Oppie

Thanks, John F !!!

I knew it was simple. I was just having a brain freeze :-) ...Jim Thompson

"Jim Thompson" schreef in bericht news: snipped-for-privacy@4ax.com...

Well, the basic idea is to use the pulse to be streched to set a flipflop (asynchronously) and to start the counter. When the counter overflows it resets the flipflop and stops the counting until the next pulse appears.

petrus bitbyter

If you want to use a counter, try a 74HC4060.

Tim.

JT says "I'm leery of RC due to leakage" which puts him as out of touch with analog design as he's out of touch with digital. Hmmmm.... what's left?

No, he doesn't understand counters.

He'd better use a spring timer.

John

Silly rabbit, it's still Winter!

Larkin has become our resident ignoramus. Behaves like he's doped up like Greasy. Shun him. ...Jim Thompson

People were skiing in shorts yesterday. It was, like, 40 degrees. You didn't really need gloves.

John

Isn't a "pulse stretcher" the thing that the paramedics use to put the injured pulse onto the ambulance?

Thanks, Rich

It was in the 40s here the other night.

Spring ahead, tomorrow night.

We had a little frost this morning. The Cherry and Pear trees have already finished blooming.