Custom microUSB power cord for raspberry pi 3

Introduction

During my first plays with Raspberry Pi 3 I wanted to have a flexible ways of powering my board with different power supplies.

There are two ways to power Raspberry Pi 3:

  • using micro USB socket – the best way, but you have to use charger with mounted micro USB male plug at the end of power cable. The RPi is also protected by fuse and power protection circuit.
  • Using GPIO pin header – easy to power from a variety of different power supplies using standard 2.54 mm female connector. Unfortunately this connections (GPIO2 and GPIO4) are bypassing 5V protection circuit and fuse, so using this pins carries a certain amount of risk of breaking your RPi.

I bought an industrial power supply Mean Well MDR-20-5 with 3.0A output,
so I needed to make my own power cable to power my PRi that will use power protection circuit on board.

Required hardware

So I bought:

RPi 3 consumes up to 750mA when under stress (source) and can power USB devices with 1.2A (source). Suggested power supply should be rated with 2.5A.

22 AWG wire should be good for powering RPi, because it can handle up to 7A (Maximum amps for chassis wiring parameter form table)

Assembling

First thing is to find a micro USB male pinout (source):

Micro USB male connector pinout

1 VCC
2 D-
3 D+
4 ID
5 GND

Now It is easy, just soldering pin 1 and 5 to power cable.

But STOP, do not power the PRi yet, you should test If  wires are soldered correctly.

Testing

Use any multimeter  with continuity testing feature.

First connect new power cable to RPi.

Second connect one multimeter probe to your 5V wire end and test continuity with second probe on:

  • first pin of micro USB female socket on RPi
  • test points PP1 and PP2

Third connect one multimeter probe to your GND wire end and test continuity with second probe on:

  • fifth pin of micro USB female socket on RPi
  • test points PP3, PP4, PP5 and PP6
RPi 3 top view
RPi 3 bottom view

Sources:

RPi 3 power consumption

American Wire Gauge current limits

Micro USB male connector pinout

Raspberry Pi 3 test points