Having trouble finding a good power supply for the raspberry pi 2

Question

Hi. I just got my raspberry pi 2 a few weeks ago and I'm having trouble finding the best power supply for it. I've tested a few I acquired over the years along with a few other miscellaneous ports.

Below are the various results I've come up with when the USB drive is plugged in. max_usb_current=1 is enabled.

1 - Generic 5V 2A adaptor (Red light blinks on pi, hard drive light stays solid then starts to blink. No sound is heard from drive. Drive is not recognized.)

2 - LG 5.1V 0.7A adaptor (Pi shuts down completely. Drive is not recognized.)

3 - Kyocera 5V 0.8A adaptor (Red light blinks on pi, hard drive lights starts to blink, beeping sound is heard from drive. Drive is not recognized.)

4 - Generic 4.5v-6.5V 0.7A adaptor (No red light on pi, hard drive light stays solid then starts to blink. No sound is heard from drive. Drive is not recognized.)

5 - Plugged into Sanyo TV V/A = ? (No red light on pi, hard drive light blinks momentarily then mounts. Connection to drive is not stable and disconnects after a few minutes or immediately after trying to access it.)

6 - Plugged into computer's USB port V/A = ? (No red light on pi, hard drive light blinks momentarily then mounts. Connection is stable and reliable.)

Yes, I know that last one would work but I thought I'd list it anyway. 4 and 5 seem to be the most interesting to me.

gdstew · Answer

You did not specify but it needs to be a 2.5" hard drive. The biggest problem with supplying a hard drive with power is when you first turn it on. It takes a lot more current to "spin up" the disks in the drive than it does to keep them spinning. I have a 160 GB 2.5" hard drive that takes 1.1 A to start up and about 400 mA (0.4 A) when reading or writing to give you some idea of the difference. Another very common problem when using USB chargers that require a separate USB "data" cable to supply the power is that the cable does not use wire that will carry that much current without dropping voltage due to the resistance of the wire. Most USB cables I have seen use 26 or 28 gauge wire (the smaller the gauge number the thicker the wire, this is usually printed on the cable but it may also be only on the packaging) and it seems fairly constant that longer cables (6') use the thinner wire and short cables (3') use the thicker wire. If you are in the states I have found that MCM electronics has a 5V 2A power supply for the Raspberry Pi that uses 22 gauge wire for $4.99 that works fine with the previously mentioned 160 GB hard drive. @Clem A USB keyboard should use less that 80 mA (0.08A) and a mouse probably about the same. I'm not sure how much current is needed for wireless keyboards and mice but it should not be much more.

gdstew · Answer

It's a little expensive but it should work just fine. I have bought several items from Adafruit and have found them to be good quality products.