# Wiring a relay to a 3.3V Nano ESP32 **URL:** \ **Category:** General Electronics\ **Created:** [January 28, 2025, 3:42am UTC](https://forum.arduino.cc/t/wiring-a-relay-to-a-3-3v-nano-esp32/1347833 "2025-01-28T03:42:41Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![jim-p](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/jim-p/32/922840_2.png) [@jim-p](https://forum.arduino.cc/u/jim-p)\ **Post date:** [March 1, 2025, 10:07am UTC](https://forum.arduino.cc/t/wiring-a-relay-to-a-3-3v-nano-esp32/1347833/22 "2025-03-01T10:07:57Z")
> [@tech\_lemming](#): > > Again, I tested it by checking voltage with a multimeter (-) on 5V DC - via leg of a breadboard and multimeter (+) on IN connected to the 3.3V leg of the breadboard. IN was connected to the 3.3V leg of the breadboard. I measured approximately 3.3 V (a little less) with a 3V to 6V motor connected to the high voltage side of the relay. All that proves is that your 5V is 5V and your 3.3V is 3.3V It may seem like its working but eventually will fail if done wrong. Up to you which way you want to go, ---
**Author:** ![tech\_lemming](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tech_lemming/32/1128690_2.png) [@tech\_lemming](https://forum.arduino.cc/u/tech_lemming)\ **Post date:** [March 4, 2025, 1:25am UTC](https://forum.arduino.cc/t/wiring-a-relay-to-a-3-3v-nano-esp32/1347833/23 "2025-03-04T01:25:42Z")
Thanks Jim, I believe the relay modules I am using have the circuitry you first provided on the board (and more). However, hardware design is not my area of expertise. My background is systems analysis and design and software development. My experience is soliciting user requirements and modeling object-oriented applications using UML Then implemented the designs as n-tier applications, coded by myself and a team of coders. The n-tier applications consisted of Oracle databases to store and serve data and enforce data type rules, a Java middle tier on a java framework to enforce business rules and dynamically write DHTML GUIs, i.e. writing code with code. None of that involved designing hardware. The app I am currently prototyping is both software and hardware intensive, With respect to hardware I am strictly a hobbyist. In a way it is an n-tier application using HTML as the GUI, javascript to enforce business rules and .json files to store and serve data. The data type rules are enforced by Arduino's C++ and JavaScript. The system will be a hybrid of a local ESP-Now network with a main hub functioning as a Webserver. The main hub of the ESP-Now / Webserver is implemented on the Arduino Nano ESP32, chosen as it has 16mb of flash memory, though the Arduino IDE doesn't do a very good job of making partitioning the flash memory easily to partition the available 16mb flash memory for app0, app1, NVS and OTAdata and littleFS. Still working on getting that done. The Arduino documentation focuses on SPIFFS and is aa clear as mud. Wireless sensors are implemented with using Xiao Esp32. What I am saying is the hardware configuration issues are intense and poorly documented. The shift in the industry to 3.3V creates additional complications as we have been discussing. I am trying to avoid designing a schematic and having PCB board made as that is not where my expertise lies. My hands are full. I believe that if this relay board was reverse engineered it would solve the questions of whether or not it will be stable controlling 12V devises while using 5 volt coils and taking 3.3v input from the ESP32. Without having any expertise in hardware design it appears to me the tracings and components are obvious. I would think that with your expertise you could draw a schematic that would resolve the whether or not it is stable if used as the distributors and tutorials say it can be used. Several people have had the same question. While I appreciate kmin's input, the schematic he provided in his recommendation to remove the jumper and ground the common pin is not the schematic for this relay module. Can it be done and are you up for drawing a schematic to determine if the relay module I am proposing has the correct circuitry to be stable and not damage the ESP32? ![image](https://europe1.discourse-cdn.com/arduino/original/4X/c/f/8/cf803d1dff159b3782fe1bdc097273b8345148a2.jpeg) Thanks in advance!! ---
**Author:** ![jim-p](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/jim-p/32/922840_2.png) [@jim-p](https://forum.arduino.cc/u/jim-p)\ **Post date:** [March 4, 2025, 10:01am UTC](https://forum.arduino.cc/t/wiring-a-relay-to-a-3-3v-nano-esp32/1347833/24 "2025-03-04T10:01:45Z")
Does the seller of the relay specify that it will work with 3.3V? ---
**Author:** ![tech\_lemming](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tech_lemming/32/1128690_2.png) [@tech\_lemming](https://forum.arduino.cc/u/tech_lemming)\ **Post date:** [March 10, 2025, 6:16am UTC](https://forum.arduino.cc/t/wiring-a-relay-to-a-3-3v-nano-esp32/1347833/25 "2025-03-10T06:16:50Z")
Yes, we established that from the start but they said it was due to the optocoupler which you said does nothing. ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [September 6, 2025, 6:17am UTC](https://forum.arduino.cc/t/wiring-a-relay-to-a-3-3v-nano-esp32/1347833/26 "2025-09-06T06:17:49Z")
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