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Electronics => Beginners => Topic started by: slowaudio on January 14, 2014, 04:07:34 pm

Title: Edge Sensitive Schmitt Trigger?
Post by: slowaudio on January 14, 2014, 04:07:34 pm
Hey everyone. This is my first post, so apologies if I'm doing this wrong.

What I'm looking to make, for a lack of better terms, is an edge sensitive Schmitt Trigger. Essentially, what I'd like to do is create some sort of transition at an edge (perhaps from VDD -> GND) and keep that state until an edge hasn't been detected for some period of time.

I've tried Googling a few different things, but haven't come up with anything useful, as of yet. I'd appreciate any help.

Thank you.
Title: Re: Edge Sensitive Schmitt Trigger?
Post by: filip_cro on January 14, 2014, 04:18:12 pm
So you want to make edge detector? Or you want it to also have hysteresis? How? Please make basic waveform drawing for input and output.
Title: Re: Edge Sensitive Schmitt Trigger?
Post by: Rufus on January 14, 2014, 04:28:18 pm
You are probably looking for a re-triggerable monostable.
Title: Re: Edge Sensitive Schmitt Trigger?
Post by: Marco on January 14, 2014, 04:31:29 pm
There is a name for the circuit you describe, it's called a retriggerable monostable multivibrator (last term sometimes omitted). You can buy them as ICs, circuits using 555 or D-flip flops implementing it are also easy to find.
Title: Re: Edge Sensitive Schmitt Trigger?
Post by: slowaudio on January 14, 2014, 05:22:38 pm
You are probably looking for a re-triggerable monostable.

After a quick inspection, it appears this is exactly what I was looking for! I'm just a EE student, so I'm still learning, I really do appreciate it.

I knew I had come to the right place, thanks guys!
Title: Re: Edge Sensitive Schmitt Trigger?
Post by: zapta on January 14, 2014, 11:00:37 pm
Does this help?

http://www.nxp.com/documents/data_sheet/74HC_HCT123.pdf (http://www.nxp.com/documents/data_sheet/74HC_HCT123.pdf)