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How to test a Schmitt triggers

alec_t

Well-Known Member
Most Helpful Member
#3
Remember to connect the inputs of any unused gates to eithe the +ve rail or -ve rail, otherwise you may get weird results.
 

AnalogKid

Well-Known Member
#4
It would take 8 different oscillator configurations to test a part to see if the gate functions work, but that still would not do things such as characterize the different threshold voltages. Which parameter(s) are you testing for? And why?

ak
 

ronsimpson

Well-Known Member
Most Helpful Member
#6
What circuit do I require to test this Ic
Turn the question around.
How would you test a 2 input NAND gate?

upload_2017-12-26_7-5-48.png

Just google 4093 oscillator.
The oscillator idea is good. It test the Schmitt Triggers function but not the 2 input NAND function.

I would probably use two switches on the two inputs and a resister + LED on the output. Only test if it is a real 2-NAND. Not test the "Schmitt Triggers".

Why do you want to test? How good of a test do you need?
 

audioguru

Well-Known Member
Most Helpful Member
#7
In my career and hobby I bought probably thousands of ICs and never found a bad one. Maybe because I buy Name Brand parts from a local real electronic parts distributor not cheap junk from ebay, Amazon or Aliexpress.

I had an equalizer product manufactured and tested. All parts were from as above. 25,000 equalizers were made and only two failed. One had a bad electrolytic capacitor and the other had its quad opamp IC mounted backwards. The final tests were very detailed and all ICs performed perfectly. The ICs were not tested before assembly.
 
Thread starter #8
I am trying to repair my welder I have got it running but I can not get the welder to change from spot mode to weld mode.
I operate the switches but no change.
The only way I know is to test all components I do not have a circuit digram.
I know what voltage is on the feed motor.and and welding torch triger.
If you can help me to find the fault I would apperiate.
If you want more information then I will try to help you out.
I need to fix this welder
Greg
 

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schmitt trigger

Well-Known Member
#9
Just google 4093 oscillator.

Mike.
A simple and reliable way to test Vth(+) and Vth(-) and understanding the hysteresis concept, as long as one has a two-channel scope. Simultaneously monitoring input and output.
I've used this trick myself.

Another, if one has multifunction generator, is to apply a triangle wave at the input. And monitor it again with a two-channel scope.
 
Thread starter #12
Owing to the being a double sided do I draw each side seperate .
I have never done this befor but willing to give it a go with the forum's help
Where do I start and what side
Thank you
 

alec_t

Well-Known Member
Most Helpful Member
#14
Google "schematic capture MacOS"
 

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