calculating the thresholds for this schmitt trigger circuit

[saksoook]

hello,
please i need help with analyzing this circuit it has a comparator with open drain output, so it acts as a schmitt trigger and i know that when the input is greater than the high threshold the output will be low (0 volt) but if the input is less than the low threshold the output will be high (5 volt) but the problem is i do not know how to calculate these threshold levels. you will find attached an image of the circuit. thank you.

 

[crutschow]

The threshold is when the voltage on the + input equals the voltage on the - input. So you just calculate the voltage at the + input when the output is at 0V and also when the output is high. That will give you the two threshold voltages.

I trust you know how to calculate the voltage at each junction on a series string of resistors(?).

 

[RCinFLA]

Output of comparitor is either pulled close to ground or open circuit (with 1k pull up to 5 vdc). You must overcome the latched state by exceeding the state bias on pin 2, + input.

As you have drawn it the two threshold points are 9.138v and 8.246 v. (the 8.246v assumes zero volts on comparitor output which won't be the case so the low threshold will be a bit higher. You need to look up the spec on V-low for a 5 mA output load on comparitor)

 

[saksoook]

Thank you all