First of all, thank you so much for your interest in my question.


The following is a schematic diagram I drew up to represent my Raspberry Pi Pico WH - LED lamp project. I am controlling one 12V LED (LED1), four 5V LED strips (LED2, LED3, LED4, LED5), one Temperature and Humidity Sensor (DHT22), and one 3V LED (LED6) using my Raspberry Pi Pico WH. One 12V LED and four 5V LED strips are used as my lamp lighting. One 3V LED is used to indicate that the Pico is connected to Wi-Fi. I am running a webserver inside the Pico, so I can remotely turn on and off individual LEDs (LED1, LED2, LED3, LED4, and LED5) as I wish + read the temperature and humidity measurements.

I have provided all my components in the "Components" section below and also given links to the items where appropriate. All the components are assembled on a breadboard.

I am using a 230VAC-IN, 14VDC-OUT power adaptor to power up the whole project (e.g., an old Samsung monitor power supply). I then use a buck converter to step down from 14VDC to ~5VDC to power up the Raspberry Pi Pico WH and four 5V LED strips, and another buck converter to step down from 14VDC to ~12VDC, to power up the 12V LED.

I would like to point out to you the following values in ammeter AB1:

When? Current flowing through AB1 Ammeter
LED1, LED2, LED3, LED4, and LED5 are Off & LED6 is On 90mA
Just the 12V LED (e.g. LED1) & LED6 are On 170mA
LED1, LED2, LED3, LED4, LED5 and LED6 are On 930mA

Also, when all the LEDs are on, the values for AA1 & AA2 ammeters are as follows:

Ammeter Current flowing through the Ammeter
AA1 350mA
AB1 170mA


In general, the lamp works as expected, whether all the LEDs are on or off. I can remotely turn on and off individual LEDs (LED1, LED2, LED3, LED4, and LED5) as I wish + read the temperature and humidity measurements.

However, on a number of occasions during the day, I noticed the Pico restarts regardless of whether any of the LEDs (LED1, LED2, LED3, LED4, and LED5) were on or off.

I have been through my code on numerous occasions and still haven't found a reason for this restarting issue. I am not entirely ruling out potential issues in my code. However, I would like to ask all electronic experts on StackExchange platform: do you find any issues in my schematic diagram below? I would be very much delighted to hear your feedback.

Please let me know if you need any other information in order to share your findings. I am happy to provide :)


schematics diagram

Thank you very much

  • \$\begingroup\$ I don't have the time to dive into the datasheets. But one thing sticks out immediately: you need to connect the [-] pin of your +12V buck converter to GND. \$\endgroup\$
    – Velvet
    Commented Mar 26 at 8:48
  • 1
    \$\begingroup\$ Also, you might want to read Rules and guidelines for drawing good schematics. Main points: GND should point downwards; add reference designators for all components (e.g. buck converters) \$\endgroup\$
    – Velvet
    Commented Mar 26 at 8:49
  • \$\begingroup\$ @Velvet Thanks for your reply. Its not necessary to connect the first buck converter's [-] to the ground. Because the 12V LED [-] is grounded anyway, it therefore completes the circuit. Did you mean to connect the MOSFTE's source pin to the first buck converter's GND? I will take note of the rules and guidelines for drawing good schematics. However, on the basic layout and flow, I can see GND1 is pointed upwards. Thank you \$\endgroup\$ Commented Mar 26 at 9:16
  • \$\begingroup\$ @Velvet I have updated the schematics to point GND to down. Thanks \$\endgroup\$ Commented Mar 26 at 9:26
  • \$\begingroup\$ Does the pico reboot when running via usb but not on your board? There’s a fair chance that the reboot is caused by code and it might not be the code you wrote. Pare it down until the reboots go away. \$\endgroup\$
    – Kartman
    Commented Mar 26 at 11:02

1 Answer 1

  • As noted in comments, the regulator absolutely needs to be grounded down. Ideally with the shortest path back to the supply ground as possible.

    You cannot place arbitrary diodes and passives in the ground path of a voltage regulator, as your comment indicates you think would be fine. Otherwise it may not work as expected/at all and even if it did, it would drag EMI noise all over the circuit.

  • LEDs require current limiting in the form of series resistors. If these are LED strips rather than LEDs, they might have that built-in. But in that case you probably should pick a different schematic symbol.

  • As for why the MCU is rebooting, there is usually an option out of reset to check the reset cause. Clock failure, low-voltage detect or similar.

    I assume that the "Rasp Pi Pico" in your schematic isn't actually a MCU but a system level PCBA with everything on it. That's not particularly helpful for trouble-shooting - I would never assume that all the various hobbyist boards out there are correctly designed to begin with, so you may have to dig into the board itself. For example there ought to be decoupling and/or bulk capacitors at the supply pins.

  • \$\begingroup\$ Thanks very much for your answer. I will certainly consider grounding the regulator. Yes, those LED strips do not need additional resistors (sorry for the confusion). Do you find anything else that is odd in my schematic diagram? \$\endgroup\$ Commented Mar 26 at 16:15
  • \$\begingroup\$ @AnjanaSilva I think you are going to have to peek closer at the system reset. Measure the reset pin with your scope when you can reproduce the problem. And also look at reset causes from the software side - if there is for example a low-voltage supply occurring then you likely have a supply problem. \$\endgroup\$
    – Lundin
    Commented Mar 27 at 7:47

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