thanks for the help guys! The circuit with the schmitt triggers works well, I even tried it with regular buffer inverters (74hc04b) works almost as good. Haven't tried the 555 method yet.
I should've mentioned why I need this. I want to use a simple beeping metronome (arion um-70) to control the tap tempo function on a digitech jamman looper. I'll be using the circuits output to switch an NPN transistor or an opto-coupler that will be connected to the tap tempo input on the looper.
Anyways, perhaps someone is curious how the input and output signals look like on a scope. I've sampled the wave-shapes at different points in the circuit at different resolutions. The schematic has the sampling points (1-6) labeled and the pictures are labeled accordingly.
Opto-C = LTV827
R1 = 10K
R2 = 4.7K
Diode = 1N4148
Cap = 22µF
next: one pulse/beep magnified 250 times:
next: after the opto-coupler