Falling Edge Detector Design?

[AzeTheGreat]

I'm looking to create a pulse when a signal goes from off to on (only, not from on to off), but I can't find any falling edge detectors, and I don't understand logic gates quite well enough to make anything compact myself.  If anyone could help, that'd be awesome.

 

Edit: Never mind, I realized I was massively overthinking this.  I'll show what I did for anybody else who tries searching for this.  I used the Rapid Pulse Former from the Useful Automation Gadgets thread, with and gates to the original source signal. 

The Pulse former is the top right of the picture and emits a signal every time it is changed from off to on, or on to off.  The and gates to the original signal form the edge detectors.  The right one is a rising edge detector, since turning the signal on means it is powered, and the pulse goes through.  The left is a falling edge detector, since the source signal is inverted.

If there's a more compact version I'd be interested as well.

[KittenIsAGeek]

There's a thread somewhere that talks about logic gates.  Lets see... I think this is it:

https://forums.kleientertainment.com/topic/83723-useful-automation-gadgets/?tab=comments#comment-970441

I think what you are looking for is a D-Latch or an NS-NOR latch.

 

[Luminite2]

I think you have rising and falling edges backwards; a rising edge is from off to on. Here you go:

Set one of the filter gates to 0.1 sec (the minimum), and set the other one to whatever length you want the pulse to be. On a falling edge (on to off), nothing will happen because the two lines will be synced up, so the XOR gate will be false. On a rising edge (off to on), the gate with the longer delay will ensure that the lines have different inputs to the XOR gate for the length of the delay, resulting in the pulse you want. NOTE: if the input signal is short, it will cut the pulse short in this design. You can put a buffer gate between the input signal and the line split to extend input pulses.

[AzeTheGreat]

13 minutes ago, Luminite2 said:

I think you have rising and falling edges backwards; a rising edge is from off to on. Here you go:

Set one of the filter gates to 0.1 sec (the minimum), and set the other one to whatever length you want the pulse to be. On a falling edge (on to off), nothing will happen because the two lines will be synced up, so the XOR gate will be false. On a rising edge (off to on), the gate with the longer delay will ensure that the lines have different inputs to the XOR gate for the length of the delay, resulting in the pulse you want. NOTE: if the input signal is short, it will cut the pulse short in this design. You can put a buffer gate between the input signal and the line split to extend input pulses.

I don't see how I have them backwards?  The bottom right wire flashes green when I change the switch from off to on (rising), and the left pulses when I change from on to off (falling).

Ok, that's definitely a more compact rising edge detector, but it doesn't produce a pulse for a falling edge case.  But I suppose just inverting the signal would give a falling edge detector.  Thanks!