ESP32 Forum

Hi,

my current heating control is based on:
- Wemos D1 Mini
- 8 x Channel Relay Board
- 5 x DHT22 / AM2301

Because I need to add more sensors, I want to replace the Wemos D1 Mini with a ESP32.
Therefore I bought this board:
https://de.aliexpress.com/item/1005004387911208.html

I want to add:
- 2 x KY-025 Reed Sensor
- 2 x IR Read Head to read my 2 Power Meters (https://wiki.volkszaehler.org/hardware/ ... tl-ausgang)
- 1 x RS485 Module (https://www.makershop.de/module/kommuni ... 5-adapter/)

The setup will be powered by a 5v /2A Power Supply.
The DHT22 / AM2301 will be powered by 5V directly from the Power Supply and will be connected via Level Shifter to the ESP32 GPIO.

The 5 new sensors will have a maximum cable length of 5 meters.
I planned to power the 5 sensors with 3.3v from the ESP32 Board.

What is the maximum power output of the 3.3v Pins? I am currently not sure what the sensors will consume.
Or should I use the same setup as for the DHT22/AM2301?

Br,
Wolf70

The total current drawn by all the sensors and components connected to the 3.3V pin should not exceed this maximum current output. If the total current exceeds the maximum limit, it may lead to instability or malfunction of the ESP32 board.

It would be best to calculate the approximate power requirements or measure the actual current consumption of each sensor. Once you have the power consumption values, you can add them up and ensure that the total current drawn by all the sensors does not exceed the maximum current output of the 3.3V pin.


If the sensors have their own power requirements and can be powered independently, you can use a separate power source (such as the 5V power supply you mentioned) to power the sensors. This will ensure that the ESP32's 3.3V pin is not overloaded.

If the sensors require a higher voltage than 3.3V, you can use voltage regulators (e.g., step-down voltage regulators) to provide the appropriate voltage to the sensors. This will allow you to power the sensors directly from the 5V power supply while ensuring they receive the required voltage.

I planned to power the 5 sensors with 3.3v from the ESP32 Board.

What is the maximum power output of the 3.3v Pins?

The ESP32 module does not provide 3.3V power. The 3.3V is supplied by the relay board to the ESP module; hence, the relay board and its voltage regulator determine how much additional current you can draw from its 3v3 rail.
Check the LDO on the board and its spec'd max. current @ 5V input, subtract 200-300mA for the ESP module and you get an estimate of how much headroom the 3v3 has.