Hello I have an power source say like solar panel with of output of 30 Volts . It should be fidin to the esp32 I/O pins . Now how can it be more safest way to do that other then the voltage divider. If the solar voltage goes beyond 30 Volts then what ? To add 3.3V zener diode to voltage divider or something else can work ?

 

I am using the following voltage divider which gives output of 3.3V at 30Volts . But when is am connecting the zener diode then the output will be around 2.5V only . What's wrong I am doing?

 

hi _mr,
What model type is the 3.3Vz?
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Yes that's the 3.3V model.. Right now I am using the development board but in future I will use only chip

 

Hi mr.
Consider the effect of leakage current in low voltage Zeners.
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Try lower values of resistors

 

7.8K and 1K Voltage divider will be ok to have 3.3V zener diode? Or it will be too lower?

 

hi mr,
What is the source resistance of the voltage driving the top of the 7k8?

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Update:
The reason for asking, is that by using lower value resistors, the resistive load may pull down the Vsource voltage if the source resistance is high.

 

What's the source resistance means ? I have an solar panel output to voltage divider and zener diode in parallel which is fed in to controller chip.

 

hi mr,
As your voltage source is a solar panel, its output resistance will be low, so the 7k8 and 1K will not load the panel.

What is the measured voltage across the 3.3V Zener with those values?
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While measuring the voltage through multimeter without connecting the chip it's readings is 30v input and 2.5V at the Output point of voltage divider with 3.3 V zener Diode connected. I am using 2 3.9K 1% Resistors in series and 1k 1% Resistor.