A Simple but Surprisingly Useful Pulse Generator

[Ground_Loop]

I have a need for long period pulses to simulate real world events.  To that end, I had two pulse generators on my bench, HP8011A and HP8112A.  The 8112 is a nice instrument and serves most needs, but the pulse period only goes out to 1s.  My 8011 would go to 20s or so.  Anyway, my 8011 failed with really complex symptoms that I really could not justify spending the time to fix.  Still needing reliable long period pulses I set out to create my own.  I stripped the thumb wheels out of the 8011, grabbed a PIC24 and knocked out what is pictured below. It is very simple in that amplitude is fixed 5vdc and only the period and pulse width are adjustable.  If I need "fancy" pulses I can use it to trigger my 8112.  The PW is quite accurate down to 20us.  Below that, the micro overhead begins to kick in.  Period is equally impressive.  With period set to 900 seconds and a four hour run, my non-scientific observation was pulse count bang on 16 at the 0 second mark as observed against my bench digital clock.  I'm using a 8MHz crystal on the PIC instead of the internal oscillator.

[RoGeorge]

Nice! 
Reminds of the "darkroom timers" for developing photographic film.

[slugrustle]

That's a nice looking box.  How did you do the square cutout, and how did you do the lettering?

What are you using for the line driver?  I'm pretty sure PIC24s don't go to 5V.

[Ground_Loop]

That's a nice looking box.  How did you do the square cutout, and how did you do the lettering?

I drew up the panel and sent it off to Front Panel Express for fab.  The thumb wheel decimal is done with a paint pen.

What are you using for the line driver?  I'm pretty sure PIC24s don't go to 5V.

No line driver, It's a 24FV not 24F.