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Blue wave on scope is used to measure the time.
Orange wave is used to display the discharging capacitor voltage.
Green wave is used to display the output.
If we close the switch, capacitor is fully charged and Opamp output is HIGH.
After closing, if we open the switch, capacior discharged through resistor.
Therefore, capacitor voltage(Vc) is slightly decreased.
If Vc < 1V , Opamp output is LOW.
To reach Vc < 1V ( Out=LOW ), we'll wait 5seconds.
Capacitor Discharging Formula
Vc= Vsupply x e^-(t/RC)
Let Vc=1V, Vsupply=5V and C=1uF
By substitution,
At t=5secs , we'll get R=3.106 M ohms.
Thank You.
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