S3 Will NOT Restart After Power Loss If 5V Pin Connected

Products & Technology
1

I am using a 2-channel SSR that requires 5V to operate. If the S3’s 5V pin is connected the S3 will NOT REBOOT after power is lost. Here are a few grabs:

no-port 5V-connected
no-port 5V-connected1953×842 235 KB

The above image shows that the port is missing because the 5V GPIO is connected to the SSR.

Screenshot 2025-10-18 at 15.20.20
Screenshot 2025-10-18 at 15.20.202146×840 226 KB

The above image shows that the port has reappeared because I disconnected the 5V hookup wire from the 5V GPIO.

Does anyone have a solution to this?

Thanks!

2

Here’s a grab of my board

IMG_1990 copy
IMG_1990 copy1920×1440 233 KB

The red lead is connected to the S3’s 5V GPIO.

Will search for 3.3V relays that I hope will fit on my enclosure board.

3

The XIAO_5V pin must be used as either a 5V input pin or a 5V output pin. When USB is connected, the XIAO_5V pin functions as a 5V output pin, so do not connect an external 5V power source. When USB is not connected, the XIAO_5V pin functions as a 5V input pin, allowing you to connect an external power source to supply power to the XIAO.
How is your wiring configured?

4

Thank you for getting back to me on this issue.

I am using the 5V pin as an output pin as shown in my hookup diagram shown next.

garden-watering-hookup copy
garden-watering-hookup copy1500×966 93.3 KB

As seen the 5V pin is powering the solid-state-relay (SSR). The circuit works as designed except when power is lost the S3 will not restart because the port is unavailable as I showed above. I think I can overcome this by using a buck-booster but would rather not if this problem can be resolved.

Thank you for your help.

5

XIAO’s GPIO operates at 3.3V, so the SSR control input must also be 3.3V. Alternatively, a 3.3V-5V level converter is required.

EDIT:
Looking it up on Amazon, I found the following description. It might just barely work with LOW=0V and HIGH=3.3V.

★High Level Module: 0-2.5V state low level relay ON, 3.3-5V state high level relay OFF; Low Level Module: 0-2.5V state low level relay OFF, 3.3-5V state high level relay ON.

6

Thank you for the feedback.

Yes, I know there are some relays that will work with 3.3V power, but I do not have one of those. I will try 3.3V-to-5V (buck) converter tomorrow and see if that will be sufficient to power the SSR.

I will report back tomorrow with the results. Thank you.

7
  1. The 3.3V control signal from XIAO appears to be amplified by the transistor circuit on the SSR board to drive the SSR. Therefore, it might work even if XIAO’s HIGH is 3.3V. You should be able to check this with the LED on the board—does the LED turn ON/OFF?
  2. The SSR board seems to require 160mA of current. What is the output current in amperes of the 5V power supply you are using?
    Please explain clearly and in detail what you did and what happened. I might be able to think of something.