Creating a sharp trigger pulse from a square wave

[k7elp60]

Is there a simple way to create a sharp trigger pulse from the leading edge or the trailing edge of a square wave. I recall a resistor and a capacitor connected, but I don't recall anything else.

 

[ChrisP58]

Yes. A series capacitor and a resistor to gnd. The capacitor couples the edge through, and the resistor resets the coupled signal back to gnd.

 

[k7elp60]

Yes. A series capacitor and a resistor to gnd. The capacitor couples the edge through, and the resistor resets the coupled signal back to gnd.

Thanks Chris.
If I put the resistor to Vcc then the trigger would be the opposite polarity. How do you select the value of the capacitor?

 

[JimB]

See the attachment.

Make the time constant CR small compared with the period of the square wave, and you will get +ve and -ve pulses as I have shown.

If you want just +ve pulses, add a diode, as shown in the second pic.



JimB

 

[ronsimpson]

Google RC time constant.
https://en.wikipedia.org/wiki/RC_time_constant

 

[Reloadron]

Is there a simple way to create a sharp trigger pulse from the leading edge or the trailing edge of a square wave. I recall a resistor and a capacitor connected, but I don't recall anything else.

Yes, as Jim B posted. You want a simple "Differentiator Circuit". That is the name.

Ron

 

[k7elp60]

Thank you all for your information, this information refreshed my old memory.
Thanks again
Ned