Oscillator Circuit - Double Pulse w/ Pause

Thread Starter


Joined Oct 9, 2011
Hi All,

New to the forum. I have only some hobby experience with oscillating circuits but this one is over my head.

I need an oscillator that will trigger two opto-couplers (H11D1). I need them to be triggered in the following sequence:

"opto 1 - pause - opto 2 - pause - pause"

The above sequence should be a 500 Hz cycle (1.67ms), with each pulse and pause of equal duration (approximately 0.33ms each in this case). The main point is to have opto 1 and opto 2 pulse for the same amount of time (with a slight pause between them) and a long pause between opto 2 pulses and opto 1 pulses (as noted above).

The attached image shows two options I've been working on. The first wave form would be supplied by a single oscillator while the second wave from would be supplied by two in phase 555 timers, though I have no idea how (or if its possible) to get them in phase.

Please let me know if anything is unclear as I may have not explained my goal very well, but I'll try to fill in the blanks.

One side note, I'd like to be able to adjust the frequency between 200Hz and 1000Hz, but this is not necessary. The main problem is with the oscillating circuitry.

Thanks for any help in advance.




Joined Dec 19, 2007
Use the 555 to trigger a CD4017 Johnson ring-counter. That will give you up to 10 time frame outputs. Diode-OR the selected outputs to your opto-couplers.

Though not the exact timing/sequence you want, the attached will give you an idea of the circuit configuration.



Last edited:


Joined Jul 17, 2007
Have a look at the attached. It's almost the same as Ken's, but it's customized for your application.

Range is roughly 200Hz-1kHz. With the pot set at roughly 1/4, you'll get around 500Hz.
I didn't have the H11D1 optos in my library, so I just threw in a couple of 4N27's. Adjust your IR emitter LEDs to suit your supply voltage and optos.

Note that I am NOT showing the mandatory 0.1uF and >1uF bypass capacitors across the 555's Vcc and GND terminals.