ESP32 Forum

Posted: **Sun Jul 06, 2025 10:52 am**

I'm using an AHT20 sensor on a battery-driven board.
As already recommended here I power the sensor with a GPIO pin. After powering I wait 50ms by calling v
TaskDelay( 50 / portTICK_PERIOD_MS );
to get the sensor up.

One hint for hidden power consumers:
On one board I needed to call rtc_gpio_isolate() for a connected onboard LED before going to deep sleep. Without that the LED showed "some light".

Posted: **Mon Jul 07, 2025 4:46 am**

What LCD?!
How much power?
If you want to actually completely switch off power (3.3V) of external devices (which you can't power directly from a GPIO pin like the AHT10), the easiest way is indeed to just hook up a P-channel MOSFET to 3.3V and a GPIO output ("high-side switch").

The LCD I have used is JHD202C, a DS3231M RTC module, AHT10 sensor and we have to save as much power as possible.

Posted: **Mon Jul 07, 2025 11:14 am**

What LCD?!
How much power?
If you want to actually completely switch off power (3.3V) of external devices (which you can't power directly from a GPIO pin like the AHT10), the easiest way is indeed to just hook up a P-channel MOSFET to 3.3V and a GPIO output ("high-side switch").

The LCD I have used is JHD202C, a DS3231M RTC module, AHT10 sensor and we have to save as much power as possible.

Also which specific MOSFETs can be used?

Posted: **Mon Jul 07, 2025 5:35 pm**

Also which specific MOSFETs can be used?

Any P-channel MOSFET with a V[th] significantly less than 3.3V (or greater than -3.3V depending on the convention used) which can conduct enough current for your needs at V[gs] = -3.3V.
The AO3401A, for example, with a V[th] of -0.9V (typ.) is cheap, available, comes in SOT23 (=small but hand-solderable), can switch a few amperes, and has ~50-60mOhm of R[ds] at -3.3V of V[gs].

(Just remember to not leave the FET's gate floating while sleeping.)

Posted: **Thu Jul 10, 2025 6:42 am**

Also which specific MOSFETs can be used?
Any P-channel MOSFET with a V[th] significantly less than 3.3V (or greater than -3.3V depending on the convention used) which can conduct enough current for your needs at V[gs] = -3.3V.
The AO3401A, for example, with a V[th] of -0.9V (typ.) is cheap, available, comes in SOT23 (=small but hand-solderable), can switch a few amperes, and has ~50-60mOhm of R[ds] at -3.3V of V[gs].

(Just remember to not leave the FET's gate floating while sleeping.)

so in the deep sleep mode, the power consumed must be in microamperes. how to manage that using ESP32Devkitc V4 and a MOSFET?

Posted: **Thu Jul 10, 2025 6:49 am**

power consumed must be in microamperes. how to manage that using ESP32Devkitc V4 and a MOSFET?

Not going to happen -> viewtopic.php?t=46102#p149079

Posted: **Wed Jul 16, 2025 12:04 pm**

power consumed must be in microamperes. how to manage that using ESP32Devkitc V4 and a MOSFET?
Not going to happen -> viewtopic.php?t=46102#p149079

so according to you is it not possible to bring the consumption down to microamperes using standard devkit boards? since most of them use a AMS1117 LDO?

Posted: **Wed Jul 16, 2025 12:45 pm**

power consumed must be in microamperes. how to manage that using ESP32Devkitc V4 and a MOSFET?
Not going to happen -> viewtopic.php?t=46102#p149079
so according to you is it not possible to bring the consumption down to microamperes using standard devkit boards? since most of them use a AMS1117 LDO?

I'm powering my boards with an external battery pack and a low power Step-Down Voltage Regulator (Pololu 3.3V, 500mA D24V5F3). It's connected to the 3.3V pin of the board, so the build-in LDO will not be active. But there can be other components on the board using some power.

Posted: **Thu Jul 17, 2025 4:52 am**

Not going to happen -> viewtopic.php?t=46102#p149079
so according to you is it not possible to bring the consumption down to microamperes using standard devkit boards? since most of them use a AMS1117 LDO?
I'm powering my boards with an external battery pack and a low power Step-Down Voltage Regulator (Pololu 3.3V, 500mA D24V5F3). It's connected to the 3.3V pin of the board, so the build-in LDO will not be active. But there can be other components on the board using some power.

But in my case I am using an LCD display as well which requires 5V so I don't think this would work for me

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