Zener Diode in Series

Hello, recently I’m trying to power up the ESP32 board with 3.3V according to the data sheet, Is it correct to connect it with a 5V Zener Diode and a Silicon Diode so that the 9V source will drops to 3.3V as below ?


Better to use a 3.3V switching regulator. It saves quite a bit of power.

Exactly, use on of these

All diodes, in detail Z-diodes, will have a lower voltage drop with lower currents. This makes them unreliable as voltage reducers. An improvement were a load resistor that assures a minimum current across the diodes, but this current is lost and wasted. Nowadays a switching regulator will provide stable voltage at high efficiency.

“9volt” smells like a 9volt (smoke alarm) battery.
They are totally inadequate to power an ESP32 board (~100mA).
A buck converter could reduce battery current draw, but still, a 9volt battery will have a short lifespan. Better power the ESP32, if you must, with four AA batteries on the 5volt/V-in/USB pin.
If you don’t use battery power, then power your ESP board with a 5volt cellphone charger connected to the USB socket.

Hi jremington, thanks for the reply, so does the diagram I draw works ? because i just trying to do it for a simple event for newbies like me and not for long term usage

Thanks for the recommendations

Hi DrDiettrich, from what i learned about Zener Diode, there are very stable as long as the current is whithin the breakdown range right ? And I also learned that zener diodes are used in voltage regulators. The diagram uses a zener diode and a diode in series, not using resistor. I’m just thinking to decrease the voltage into 3.3V to supply the Esp32, in that case is it working for short term usage without damaging the board and without short circuiting on the batteries ?

Hi Wawa thanks for the reply. Actually i have tried supply it with 2 AAs (3v in total) but it doesn’t work. The usb cable and power bank works. I even tried to put the 9V battery directly without regulating the voltage but I’m afraid it will cause permanent damage as the datasheet shows range of (3.3V-3.6V). And minimum current of 0.5A.

Since the purpose is to make a RC ship model, I try to make it without cellphone charger in case accidents happens.

After all, does the diagram i draw works in order drop the voltage from battery into 3.3V without damaging the board, diode and short ciruiting ? I believe the rest 3.3V will be manage properly by the esp32 board.

Hi Crossroads, as long as the power rating and maximum voltage rating satisfy the datasheet, it shouldn’t be a problem right ?

I thought a way without using Zener diodes, that is 3AA Batteries (4.5V in total) connected with 1 Silicon Diode and 1 Germanium Diode so that the voltage become Vsupply = 4.5V-0.7V-0.3V = 3.5V.

Is it correct to think like this ?
(As the zener diode usually have power rating lower than 1W, Esp32 requires 0.5A which is not very suitable for a 9V battery )

The bare ESP32 module requires 3.3volt, but you mention an ESP32 board.
All ESP32 development boards I know require 5volt. So what do you have.
ESP32 boards could run on four AA batteries.

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If you have a development board like this;doitesp32

Then this may help:

Tom… :grinning: :+1: :coffee: :australia:

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That implies you have some other power source on the ship to power servos, motors, etc. Why not power the esp32 from that?

@ yew_qi_ming,
I’m not a fan of diodes as regulators. The voltage drop across them can vary with current, and when the source voltage is large, then a lot of battery capacity is just wasted as heat across the diode and resistor.
Do it the right way, get a switching regulator, they are 85-90% efficient and will give you more run time from the battery. They are also very small.

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Ok got it

Actually i just trying to run it with two dc motors for the first time, but anyway i found there is a voltage regulator on top so within the range should be no problem, that means no need diodes.

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