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KVL rules here. The zener branch (R1 and D1) will be at the same voltage as the capacitor branch (D2, R2, and C1), which will be 9V.

If you want the zener to limit the cap voltage, you need to move D2 to the midpoint junction of R1 and D1.

^{simulate this circuit – Schematic created using CircuitLab}

Don't forget that D2 will eat a few hundred millivolts, meaning your cap voltage could end up as 1.6V or so.

R2 is redundant with a charge resistance of 100.1k. I would use a 6.8 volt zener or two white Leds in series to charge C1 and drop R1 and diode and keep R2=100. The brightness of led shows charging and no current is wasted when charged. It is not precise and voltage may rise to 3V when dim.

KVL rules here. The zener branch (R1 and D1) will be at the same voltage as the capacitor branch (D2, R2, and C1), which will be 9V.

If you want the zener to limit the cap voltage, you need to move D2 to the midpoint junction of R1 and D1.

^{simulate this circuit – Schematic created using CircuitLab}

Don't forget that D2 will eat a few hundred millivolts, meaning your cap voltage could end up as 1.6V or so.

Once you get the basic idea of how the zener clamp works, you can start playing around with the resistor values (hint: is R2 really necessary?) and see how the performance is impacted.

KVL rules here. The zener branch (R1 and D1) will be at the same voltage as the capacitor branch (D2, R2, and C1), which will be 9V.

If you want the zener to limit the cap voltage, you need to move D2 to the midpoint junction of R1 and D1.

^{simulate this circuit – Schematic created using CircuitLab}

Don't forget that D2 will eat a few hundred millivolts, meaning your cap voltage could end up as 1.6V or so.

KVL rules here. The zener branch (R1 and D1) will be at the same voltage as the capacitor branch (D2, R2, and C1), which will be 9V.

If you want the zener to limit the cap voltage, you need to move D2 to the midpoint junction of R1 and D1.

^{simulate this circuit – Schematic created using CircuitLab}

Don't forget that D2 will eat a few hundred millivolts, meaning your cap voltage could end up as 1.6V or so.

R2 is redundant with a charge resistance of 100.1k. I would use a 6.8 volt zener or two white Leds in series to charge C1 and drop R1 and diode and keep R2=100. The brightness of led shows charging and no current is wasted when charged. It is not precise and voltage may rise to 3V when dim.

KVL rules here. The zener branch (R1 and D1) will be at the same voltage as the capacitor branch (D2, R2, and C1), which will be 9V.

If you want the zener to limit the cap voltage, you need to move D2 to the midpoint junction of R1 and D1.

^{simulate this circuit – Schematic created using CircuitLab}

KVL rules here. The zener branch (R1 and D1) will be at the same voltage as the capacitor branch (D2, R2, and C1), which will be 9V.

If you want the zener to limit the cap voltage, you need to move D2 to the midpoint junction of R1 and D1.

^{simulate this circuit – Schematic created using CircuitLab}

Don't forget that D2 will eat a few hundred millivolts, meaning your cap voltage could end up as 1.6V or so.