Powersupply for Raspberry Pi

Discussion in 'General Electronics Chat' started by nerdegutta, Oct 20, 2014.

  1. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    Hi.

    I'm working on some Raspberry Pi ideas, and I've made a schematic of what I think might work as a powersupply.

    I'm planning on using a 12v 5.0Ah or a 12v 33Ah battery.

    Rpi_sch.png Rpi_brd.png

    I'm not quite sure about the powerpins on the USB part.
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    What is wrong with using almost any 5V mobile phone charger? Or the supply that came with the Pi?

    My supply - from CanaKit (Pi Kit supplier) is 1 amp at 5.1 volts but 0.5 amp works if you are only using a mouse and Keyboard as USB input devices.
     
  3. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    Nothing wrong with that, and I will use it when I have access to it. I'm planning on using the RPi in the forest. Off the grid. :)
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    If you're planning on drawing 1A from the 5V supply then the regulator would have to dissipate 7W. It would need a LARGE heatsink. Your circuit board doesn't seem to make allowance for any heatsink. The 1N4004 will be running at its rated maximum; not good practice.
     
  5. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    I read somwhere that is uses something between 500-800mA. Adding a heatsink, will not be any problem. Of course that mA is dependent on what I'm hooking up to it. For now, its only that Pi Cam.
     
  6. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    If the Pi does not draw more than 1 Amps, you are fine but as said before a large heat sink is advised.
     
  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    DO NOT POWER UP WITHOUT CONFIRMING USB PIN LAYOUT.
    Do some research on Pi. I do not eat any RPi :p so I cannot confirm
     
  8. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    OK, so I'll make room for a heatsink. How about the USB connection. Have I managed to read the datasheet right? Regarding the +5vdc and gnd?
     
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Share the DATA. I will check right now
     
  10. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    This:
    subpinout.jpg

    I got an USB A PCB mount. The one on the top right corner.
     
  11. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    I thought Pi Data...sorry.
    Jen, I am at home so I cannot confirm with DVM as the USB power connections reverses depending on USB port orientation.
    The Data you posted is the same type used on the laptop I am on right now. So I am not going to say you are right cause I am just not sure your USB PCB jack is a reversed pin one or the common types used.
    I can test tomorrow with the DVM at work shop if you like but I need to see a picture of the USB jack u planned to use
     
  12. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    OK, this is my USB:
    myUSB.JPG
     
  13. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Aah. OK
    So the Pi works through a PC USB Port, right ?
     
  14. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    Yes, well that's a truth with modifications. A PC USB cannot deliver enought AMPS. Oh, well perhaps the 3.0 standard can. My plan was to connect it to a battery, 12v, and run the power through some caps and a LM7805 and som caps again. Right now I'm using an old cellphone charger with 700Ma ratings on it.
     
  15. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Cell phone chargers and Laptops have same pinout.
    So you wanna confirm the positive pin, still ?
     
  16. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    Guess I've managed to connect the +5 to the right pin... A second pair of eyes couldn't hurt... :)
     
  17. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    OK then, I will confirm tomorrow with the DVM. Compare your jack to that of a PC or charger.
    Till then ta ta...!
     
  18. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    Thank you.
     
  19. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    One more thing.
    I normally use a 100nf and a 10uf at input and output of the 7805 for decoupling.
    Adding a 10uf might be good. The decoupling caps should be as close as possible to the 7805. The 100uf can be used at output only as you are using a battery as the source.
    Bring the 100nf close to the Regs at Input and output (like as close to 7805 pins). Then place the 10uf. And if you prefer you can add a 100uf at the USB Port pins and the cathode pin of the protection diode.
     
  20. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Crap...I forgot. Do add a 1 Amp fuse before the Diode. A fast acting one.
    Remember you are gonna using a Battery which can burn the Regulator with a smile

    I guess you need to re arrange the PCB layout to add a Heatsink. Cause @700mA, the 7805 will get hot to touch u know.
     
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