DC Barrel to Micro USB

[spadge_2356]

Hi All,

After my last thread I posted about having power issues, I managed to solve it by buying a better power supply for my USB powered hub.

I've been wondering this week, if I could use the Pi without the hub and just power it using the micro usb. Unfortunately the existing power supply (5v 3A) has a 5.5mm barrel connector. So I soldered together a female USB connector to a female 5.5mm DC Barrel so I could try and connect power this way.

It worked at first, however after it boots up into Raspbmc the Pi resets when the GUI tries to load up. I have read the forum posts that say DC barrel's sometimes provide intermittent voltage could this be the problem? If this is the case what can I do to fix the issue?

[Wheel_nut]

What are you powering "through" the RPi USB, GPIO and HDMI Connectors?

THe problem with powering all of your peripherals through the MicroUSB connector is that you are likely to encounter excessive volt drop through the F3 Polyfuse. Also, many MicroUSB cables have exccessively high resistance conductors and can give you reduced voltage at the TP1-TP2 test points on the board.

You would be better to power your RPi through either the GPIO connector or back-feed one of the USB A sockets.

[spadge_2356]

What are you powering "through" the RPi USB, GPIO and HDMI Connectors?

On this occasion I want to power the RPi using the micro USB port (not been able to do this without a USB hub which is what I'm trying to do now essentially). Connected to the Pi is the HDMI for the screen, RJ45 for ethernet, and a single USB peripherial (keyboard), and nothing else accept the micro USB.

THe problem with powering all of your peripherals through the MicroUSB connector is that you are likely to encounter excessive volt drop through the F3 Polyfuse. Also, many MicroUSB cables have exccessively high resistance conductors and can give you reduced voltage at the TP1-TP2 test points on the board.

I suspected as much from reading the previous topics in the forums so I tested the supply. The input voltage is actually 5.5v, and across TP1/TP2 the voltage is 4.6v, I'll measure the resistance across the polyfuse tonight to see if that's the problem.

You would be better to power your RPi through either the GPIO connector or back-feed one of the USB A sockets.

I agree, I already have a working setup where the power supply is plugged straight into the USB hub and from there a USB to micro USB cable to the power socket on the Pi. However it negates the purpose of my little experiment. I don't see why I can't do what I'm aiming to achieve? What does the powered USB hub have that my project doesn’t? Perhaps power needs to be fed into both USB and Micro USB for it to work?

[RaTTuS]

just power the RPi via the GPIO if you want to get creative - it bypasses the fuses - but makes for a smaller footprint.

[Wheel_nut]

I agree, I already have a working setup where the power supply is plugged straight into the USB hub and from there a USB to micro USB cable to the power socket on the Pi. However it negates the purpose of my little experiment. I don't see why I can't do what I'm aiming to achieve? What does the powered USB hub have that my project doesn’t? Perhaps power needs to be fed into both USB and Micro USB for it to work?

Instead of making up a 5.5mm Barrel to MicroUSB adapter, why don't you make up a 5.5mm Barrel to USB A Male connector and plug it into the spare USB Socket on the RPi. You would not need to power the MicroUSB socket at all as you would be back-feeding the USB socket and bypassing the F3 Fuse.

[spadge_2356]

I agree, I already have a working setup where the power supply is plugged straight into the USB hub and from there a USB to micro USB cable to the power socket on the Pi. However it negates the purpose of my little experiment. I don't see why I can't do what I'm aiming to achieve? What does the powered USB hub have that my project doesn’t? Perhaps power needs to be fed into both USB and Micro USB for it to work?

Instead of making up a 5.5mm Barrel to MicroUSB adapter, why don't you make up a 5.5mm Barrel to USB A Male connector and plug it into the spare USB Socket on the RPi. You would not need to power the MicroUSB socket at all as you would be back-feeding the USB socket and bypassing the F3 Fuse.

I know its been a while since I posted on this thread but only just got round to doing this. Unfortunately this doesnt work either I get kernel panic - not syncing, and EXT4-fs (mmcblk0p3); error loading journal. I cant understand why this wont work?

[spadge_2356]

ahhh just realised why I am getting errors now. I've managed to brick both my SD cards somehow. It did boot up succesfully on the first attempt but it rebooted and on the reboot it started giving me the errors.

Why cant I run the Rpi without a powered hub? I don't even have peripherals attached to it, yet I still need a 3A power supply, a USB hub and a USB cable from the hub to the micro usb power socket on the Pi just to get it running properly.