Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Improvised symbol for Schmitt trigger

Status
Not open for further replies.
R1=Vhys*R2/Vcc

Hi,

Using that formula, the hysteresis voltage would be:
Vhys=Vcc*R1/R2

and with R1=1M and R2=3M and Vcc=15 we get:
Vhys=15*1/3=5v

so the low trip point is Vcc/2-Vhys/2=7.5-2.5=5v and the top trip point is 7.5+2.5=10v.
This means the inputs do not get recognized as a logic high until the input reaches 10v.
After that, a low will not be recognized until it reached down to 5v.
So to see any change an input would have to go to around 11v and down to around 4v to make sure.
That is assuming that the output goes all the way to zero and all the way to 15v when it switches.

Try again and see what happens. It also may not work as well like this with only one feedback path, we might have to use two separate Schmitt Triggers on the input for correct operation to keep the trigger action independent for each input channel.


The purpose of Schmitt Trigger inputs is to help prevent false triggering from slowly increasing or decreasing signals. A slow signal on a regular gate could make the input seem ambiguous to the gate and thus cause the output to jump up and down while it moves through the threshold region. The hysteresis means that once it switches, it stays at that logic state until the input again changes more drastically which would normally mean a real signal not just noise.
 
Heck, I can't even read about them. How about posting the datasheet? Apparently, the robo-responses indicate I can get 5000 from China at very low cost. ;)
Of course, I don't know what I would do with all of those DIP parts with nothing inside.
John
 
Hi,

Yikes. Could i have posted the wrong part number all along? My sincerest apology. Try 74HC7002.

Heck, I can't even read about them. How about posting the datasheet? Apparently, the robo-responses indicate I can get 5000 from China at very low cost. ;)
Of course, I don't know what I would do with all of those DIP parts with nothing inside.
John

https://www.ti.com/product/sn74hc7002
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top