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Most commen octal buffer with schmitt trigger

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Pax Writer

New Member
Hi experts

I hate to have to ask this rather lame question, but somehow I haven't been able to come up with a good answer on the rest of the net...
I'm building a project where I need an octal buffer with a schmitt trigger.
The inputs are hooked up to phototransistor switches and the outputs will trigger the interrupts of an ATMega8 through two wired-logic OR-gates. The whole circuit is run on 5V just to clarify.
Finding such a chip doesn't seem to be a problem, however, I want to use the most commonly available chip, so I never have to worry about the supply running out (at least a while ahead). In my prototype, I'm using a 74HC7541, but my local supplier doesn't have it.. In fact I'm not quite sure where I have mine from...
Anyway, which chip would you suggest?

Thanks in advance.
 

ronsimpson

Well-Known Member
Most Helpful Member
Digikey.com has 6,000 parts (74HC7541)

You could try using the 74hc7540. It is an inverter. You will need to invert in software.
 

Pax Writer

New Member
Hi

Thanks for the tip. I live in Denmark and prefer to use Danish suppliers to cut the shipping costs, but I'll look at digikey and check out how much I'd have to bleed to get a bunch of theirs.

Pax
 

Hero999

Banned
Have you tried searching for an octal buffer?

You can make it into an schmitt trigger by adding a couple of resistors per buffer.

EDIT:
What would be the point of that? You want a simple IC solution.
 

Pax Writer

New Member
@Ron: Thanks, I just commenced the catalogue download. The page is a little slow from my terminal, so this'll probably save me time in the long run :)

@Hero: Did you just edit an answer for your own post? :) Well, you are right, I prefer a simple solution, although this project will eventually have a PCB designed for it. Saves time on mounting and parts. However, I am surprised at how hard it apparently is to find a common, non-inverting buffer with schmitt trigger. I thought the problem would be to decide which to use. The easy thing would be to simply use gates because they have high enough impedances in their inputs to look like buffers for the uCPU inputs in the other end, but the problem is that I still don't quite know if I'll need 2 2-input OR-gates or 2 4-input OR-gates. Once my proto is complete I'll know. So far I guess I'll have to make do with the 74HC7541 and the diodes...

Thanks for your answers.
 

ericgibbs

Well-Known Member
Most Helpful Member
hi Pax,
I posted a reply yesterday, it must have gone into a 'black hole'!:eek:

According to my datasheets the HCT64X series have schmitt inputs.
I realise that they are octal transceiver buffers, but they offer an alternative solution.
 

Pax Writer

New Member
Hi Eric: I didn't see that mail, sorry :) However, your idea is not bad. Being transcievers, I bet the direction of the IC is determined by one or more pins which could be tied to the relevant net (GND, +5V) to keep them going one way. I'll download the datasheet and take a look. Thanks a lot for your time :)
 

mneary

New Member
For decades, some form of 74xx244 has been awfully common. Schmitt trigger, but switching point is kind of loose and the hysteresis is fairly small.

At work, I use a lot of 74HC14, but it's only 6 sections.
 
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