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2784Re: [Raspberry_Pi_4-Ham_RADIO] RE: Preparing to purchase Raspberry Pi

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  • Tim McDonough N9PUZ
    Feb 7, 2014
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      In addition to the current capability of your power supply you need to be aware of how much current your peripherals try to draw through the R-Pi. The power input line connected to the micro USB power connector has an inline PTC (polyfuse) rated at 1.1A 6VDC.

      A schematic of the R-Pi Rev. 2.0 boards is available here:


      In most applications I have not needed a powered hub either. However, I do have one R-Pi on my network that has no mouse, keyboard, or wireless but it does have an external 1TB USB disk drive. I ended up using a powered hub for the drive because the disk would not always initialize and come online.


      Tim N9PUZ

      On 2/6/2014 2:33 PM, Max Harper wrote:
      The statement "You will also need an external USB powered hub for the keyboard and mouse.�� The pi USB port is limited in current." is questionable. No, you can't draw the 500ma that USB is speced for, but that usually is not the real problem. I have seven Raspi and don't use a powered hub on any of them. I have all kinds of devices connected to them. Some have un-powered hubs where I needed more ports. They are all powered with a power supply from Adafruit and I don't have the problems that I read about daily. This supply is set at 5.25V to make up for the voltage drop in the cable.
      The Raspi should have had an onboard regulator. It would have eliminated most of the power related problems. Trying to run one off of a cheap cell phone charger that has poor regulation is where most of the problems begin. There is a difference between a charger and a power supply.
      Max KG4PID

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