I am mikek's Blog

The personal blog of Mike Karthauser, who you may know from Brightstorm Limited or the internet.

Getting more power for the Pi

I’ve been mostly connecting to my Raspberry Pi via terminal on SSH.

As running x windows is desirable sometimes (to use scratch for example) we’ve pulled out the keyboard and mouse (an apple pair in this instance) plugged these into the Pi and then connected the video out to our Samsung HDTV.

Things aren’t so smooth this way. I’m getting issues with what seems like keys sticking down and the Pi not registering my key presses which is infuriating and makes even simple tasks like logging in impossible. A bit of a scout round the web and I find out I’m running out of power.

As the USB sockets on the Pi only put out 100mA then we don’t have enough power to run both mouse and keyboard off the socket. As I’m also running wifi off the USB then I suspect this is also limiting the power I can get for my Pi.

The solution here is to get more power into the system by using an external powered USB hub and connecting my mouse and keyboard into this.

I could also use a lower powered keyboard as per this post
http://elinux.org/RPi_VerifiedPeripherals#Working_USB_Keyboards.

The voltage drop is explained in this post

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=26&t=22413

.. is caused by the volt drop between your PSU and the RPi, across the RPI MicroUSB socket Polyfuse and then the cabling to your Hub and Keyboard. I use a POWERED Hub and then power the RPi by backfeeding the USB sockets. This way you circumvent the volt drop inherent in MicroUSB cables, the plug/ socket and the RPi’s Polyfuse. The repeating characters from the keyboad usually occur when the Voltage drops below ~4.7 Volts.

I’m off to rummage through my box of hardwear cruft to find an old powered hub to see if this sorts it out

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Filed under: raspberry pi

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