afbase
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AC 115V adapter to USB 5V, 700ma

Mon Jul 16, 2012 1:38 am

Does anyone recommend a well built AC adapter for power to Raspberry pi's?

I have one for my cell phone (LG adapter), but it is old and the output is 5.1V, 700ma. Secondly, i have two Pi's (perhaps a third one as well).

My concerns for power are these:
1) the first pi will be for a server. It will need a SD card, ethernet cable, and a USB stick or hard drive
2) the second pi will ultimately be for computer vision. a camera as visual and perhaps ethernet to other devices for communication.

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mahjongg
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Re: AC 115V adapter to USB 5V, 700ma

Mon Jul 16, 2012 2:16 am

5.1 Volt shouldn't be a problem. and 700mA is normally enough for a PI and simple low power USB devices, but if its old maybe the electrolytic capacitor in it has dried out, and it capacity has deteriorated. There should be no ripple on the regulated 5V when loaded at 700mA, or all kinds of crazy problems can occur. Its also reported that its better to have a double isolated PSU, not one with a safety ground.

afbase
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Re: AC 115V adapter to USB 5V, 700ma

Mon Jul 16, 2012 3:33 am

mahjongg wrote:5.1 Volt shouldn't be a problem. and 700mA is normally enough for a PI and simple low power USB devices, but if its old maybe the electrolytic capacitor in it has dried out, and it capacity has deteriorated. There should be no ripple on the regulated 5V when loaded at 700mA, or all kinds of crazy problems can occur. Its also reported that its better to have a double isolated PSU, not one with a safety ground.
  • I have no idea what a double isolated PSU is. Can you link me to one? Would you give me a brief summary of what it is.

    Secondly, I found this device on Newegg. Does this work as a PSU for a R-Pi? Link

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pluggy
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Re: AC 115V adapter to USB 5V, 700ma

Mon Jul 16, 2012 7:21 am

You'd be hard pushed to find a phone charger / similar PSU that isn't double insulated (or isolated if you like) - I've certainly never seen one. In this part of the world they have a square in a square symbol marked on them.

Image

Since this forum insists on shrinking posted images, here a full size link :

http://www.pluggy.me.uk/photo/doubleinsulated.jpg

http://en.wikipedia.org/wiki/Appliance_classes - see under 'Class II'
Don't judge Linux by the Pi.......
I must not tread on too many sacred cows......

afbase
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Re: AC 115V adapter to USB 5V, 700ma

Mon Jul 16, 2012 1:36 pm

pluggy wrote:You'd be hard pushed to find a phone charger / similar PSU that isn't double insulated (or isolated if you like) - I've certainly never seen one. In this part of the world they have a square in a square symbol marked on them.
Thanks for your reply. Now I know what to look for. :D

Ocean20
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Re: AC 115V adapter to USB 5V, 700ma

Wed Jul 18, 2012 3:54 am

You could use an Apple mains power adaptor that accepts between 100 VAC to 240 VAC and outputs 5 VDC @ 1 amp then connect a USB cable that terminates in the right sort of mini USB connector to plug into the rpi power port. If you go to https://lh5.googleusercontent.com/-BcLK ... +micro.png there is a picture on the right that shows the correct connection for the rpi power port.

itimpi
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Re: AC 115V adapter to USB 5V, 700ma

Wed Jul 18, 2012 7:48 am

Ocean20 wrote:You could use an Apple mains power adaptor that accepts between 100 VAC to 240 VAC and outputs 5 VDC @ 1 amp then connect a USB cable that terminates in the right sort of mini USB connector to plug into the rpi power port. If you go to https://lh5.googleusercontent.com/-BcLK ... +micro.png there is a picture on the right that shows the correct connection for the rpi power port.
Your picture is correct - but you talk about a mini-USB when you mean micro-USB (they are different). Just thought I should clear this up in case anyone uses the wrong search term when looking for a suitable cable.

RichA
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Any idea why the USB instead of minidin?

Thu Jul 26, 2012 9:42 pm

I presume there is a need for more than just +/- leads?

khh
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Re: Any idea why the USB instead of minidin?

Fri Jul 27, 2012 7:39 am

RichA wrote:I presume there is a need for more than just +/- leads?
No, the raspberry pi does not have the communication part of the micro-USB socket connected to anything. You just need a microUSB that can output 700 or more mA. Personally I just got the recommended 1200 mA PSU from RS Components when I ordered it (convenience), but it shouldn't be hard to find a suitable one in any electronics store.

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Jim JKla
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Re: AC 115V adapter to USB 5V, 700ma

Fri Jul 27, 2012 7:48 am

If you want to run a Pi as a server you only need a powerlead and a network 10baseT Ethernet you can do all of you setup/maintainance over an ssh connection theres info on the wiki for the Wheezy Beta in noob understandable language.
Noob is not derogatory the noob is just the lower end of the noob--geek spectrum being a noob is just your first step towards being an uber-geek ;)

If you find a solution please post it in the wiki the forum dies too quick

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