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I'm running a Raspberry Pi 3B+ on a 24V 3.3Amp LED Driver. I'm converting the 24V to 5.1V for the Pi using an MP1584EN DC-DC Buck Converter with a rated output current of 3Amp. I power the Pi though the Micro-USB using a a connector with only the +DC and -DC contacts connected.

My questions is this. My Raspberry Pi boots and operate correctly but the PWR LED is not on. It flashes on boot but is not on during normal operation.

Is something wrong?

  • The MP1584EN has an adjustable output voltage that's determined by the voltage divider connected to the FB pin. When you say its output is 5.1 V, does that mean you've measured the output voltage at 5.1, or you've calculated it to be 5.1 V? – Seamus Aug 6 '18 at 12:53
  • Yes, I connected to the unit to my multimeter and adjusted the output via the potentiometer until it reached 5.1V. So I have measured it to be 5.1V. – Sam Aug 6 '18 at 13:02
  • Just trying to cover all the possibilities here: 3 questions: Q1: Where did you take that measurement with a load connected; i.e. on the RPi, or at the output of your PS? Q2: Was the RPi powered on when you took this reading? Q3: Are there any other loads on the LED driver other than the MP1584EN... anything that may cause its output to change (and therefore input to the MP1584EN)? It is a regulated supply of course, but that regulation is subject to limits. – Seamus Aug 6 '18 at 19:20
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When using a buck converter, I much prefer supplying power to the 40-pin extension header.. I originally used the micro-USB but eventually got annoyed at the mechanical instability of that connection. I now apply 5.1V to pin 4 and GND to pin 6. I no longer use the micro-USB for anything.

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Your module is not suppling 5V it is less than 4.7V

See Raspberry Pi Power Limitations

  • I am open to the possibility but according to my Multimeter (<1 Year Old) it is definetely 5.1V? – Sam Aug 6 '18 at 13:03
  • If the voltage (measured between pin 2, 6) is 5.1V the LED will be ON. NOTE this is HIGHER than recommended MAXIMUM. See link for detailed possibilities - possible high resistance cable. – Milliways Aug 6 '18 at 14:32

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