I am wanting to calculate the hysteresis of a non-inverting Schmitt Trigger using a LM358 on the circuit below:
According to the resistor/voltage divider, the voltage drop across R1 will be about 8.16 volts and the reference voltage at node A will be about 3.84 volts (12v minus 8.16v)
The voltages at node B will vary between 0 volts and 6 volts.
I have found the links below to calculate the voltage high and voltage low outputs.
1. http://www.pcbheaven.com/drcalculus/index.php?calc=st_nonsym_sp
2. http://hyperphysics.phy-astr.gsu.edu/hbase/Electronic/schmitt.html#c2
3. https://howtomechatronics.com/how-it-works/electrical-engineering/schmitt-trigger
Using the boxes in link 1 and using values of 'Supply voltage' = 5 volts, R1 = 10k, R2 = 10k, R3=10k
I am getting:
V High= 3.333333 Volt
V Low= 1.666667 Volt
and using the same values 'Supply voltage' = 5 volts, R1 = 10k, R2 = 10k, R3=10k in link 2
I am getting:
the trigger voltage will be
= 3.3333 Volts
and it will hold until the signal drops to
= 0 Volts
When I enter values into these input boxes on these websites I am getting different results or am I missing something!?
So if I use the boxes in link 1 for my circuit ..that is Supply voltage = 12, R1 = 10k, R2 = 4.7k, R3 (RFB) = 220k
I get.. **** = the same, ~~~ = different
V High= 3.953673 Volt ****
V Low= 3.781774 Volt ~~~
whereas when I enter the values in link 2 I get...
V2 = 3.953 volts ****
V'2 = 3.6098 volts ~~~
Also I do not understand what the '||' means in the formulas in link 3
look under Non-Symmetrical Schmitt Trigger
can someone enlighten me?
So basically what is the correct formula?
According to the resistor/voltage divider, the voltage drop across R1 will be about 8.16 volts and the reference voltage at node A will be about 3.84 volts (12v minus 8.16v)
The voltages at node B will vary between 0 volts and 6 volts.
I have found the links below to calculate the voltage high and voltage low outputs.
1. http://www.pcbheaven.com/drcalculus/index.php?calc=st_nonsym_sp
2. http://hyperphysics.phy-astr.gsu.edu/hbase/Electronic/schmitt.html#c2
3. https://howtomechatronics.com/how-it-works/electrical-engineering/schmitt-trigger
Using the boxes in link 1 and using values of 'Supply voltage' = 5 volts, R1 = 10k, R2 = 10k, R3=10k
I am getting:
V High= 3.333333 Volt
V Low= 1.666667 Volt
and using the same values 'Supply voltage' = 5 volts, R1 = 10k, R2 = 10k, R3=10k in link 2
I am getting:
the trigger voltage will be
and it will hold until the signal drops to
When I enter values into these input boxes on these websites I am getting different results or am I missing something!?
So if I use the boxes in link 1 for my circuit ..that is Supply voltage = 12, R1 = 10k, R2 = 4.7k, R3 (RFB) = 220k
I get.. **** = the same, ~~~ = different
V High= 3.953673 Volt ****
V Low= 3.781774 Volt ~~~
whereas when I enter the values in link 2 I get...
V2 = 3.953 volts ****
V'2 = 3.6098 volts ~~~
Also I do not understand what the '||' means in the formulas in link 3
look under Non-Symmetrical Schmitt Trigger
can someone enlighten me?
So basically what is the correct formula?
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