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SOLVED GPIO connection, is 5V pin needed?

Discussion in 'Hardware Support' started by siz, 4 August 2016.

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  1. siz

    siz New Member

    Messages:
    25
    Hardware:
    RPi2
    Hey,

    I have ordered a 5V 10A adapter and a 4M 30 leds/m WS2801 strip, and I am doing some initial research.
    When looking at diagrams for a RPi with no video caption, it's:

    [​IMG]

    Atm my OpenELEC RPi 2 system is connected to my TV's 900 mA USB for power, so it starts automatically and switches to the RPi which I prefer. If I follow the above diagram when I receive the gear, then the RPi gets powered through the GPIO.

    However, can't I just ignore the +5V and GND to the RPi GPIO? Then just connect the MOSI and SCLK to the strip, and the led strips GND and +5V to the DC adapter? Or do the led GND need to be connected to RPi also?

    Thanks in advance :D
     
  2. TPmodding

    TPmodding Administrator Staff Member Administrator

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    1,890
    Hardware:
    RPi1/Zero, RPi2, RPi3, +Arduino, +nodeMCU/ESP8266
    Yes you are right, you can ignore the 5V but the connect the GND. But i woul recommend you to use the 5V from the DC Adapter, cause 900mA are to low for the RPi...if you dont see the rainbow dice on the right corner than are the 900mA enough
     
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  3. siz

    siz New Member

    Messages:
    25
    Hardware:
    RPi2
    Thank you, I will take that into consideration :D
     
  4. siz

    siz New Member

    Messages:
    25
    Hardware:
    RPi2
    One more thing. In the official tutorial, the LED strip end's 5V+ and GND gets connected back to the DC, is this a necessary step? regular LED strips do not need this.
     
  5. Brindosch

    Brindosch Active Member

    Messages:
    658
    Hardware:
    RPi1/Zero, RPi2, RPi3, +nodeMCU/ESP8266
    It is recommended to attach power at the end again, as voltage drops slowly until the end. Which result in a brightness shift.
     
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  6. siz

    siz New Member

    Messages:
    25
    Hardware:
    RPi2
    Seems logical. Thanks for the input :)
     
  7. siz

    siz New Member

    Messages:
    25
    Hardware:
    RPi2
    Got my ws2801 leds today, still waiting for the dc adapter :) I soldered the start strip with a 4 pin JST SM female connector and the 2 next with 4 wires. The end of the last strip where Gnd and 5V go to DC, isn't fine that I just soldered those two to the start strip's Gnd and 5V?

    [​IMG]
    So Gnd and 5v loop around, and Ci and Di stop at last strip. Instead of them directly going to dc adapter, as they get connected via the jst female connector to 5v and Gnd. Then I will solder a male jst connector to dc and RPi.

    Properly an obvious question, but been some time ago I've worked with electricity, so just wanna be sure :D
     
  8. siz

    siz New Member

    Messages:
    25
    Hardware:
    RPi2
    Any ideas to the above question?

    Received the needed cables for the last jst connector, I want to solder it and be ready, so when I get the dc adapter I just need to plug it in.
     
  9. penfold42

    penfold42 Active Member

    Messages:
    746
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    Yes
     
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  10. iiidefconiii

    iiidefconiii Member

    Messages:
    106
    Hardware:
    32/64bit, +Arduino
    This with an extra adapter at the end or like the picture from siz?
     
  11. siz

    siz New Member

    Messages:
    25
    Hardware:
    RPi2
    No extra adapter.
     
  12. iiidefconiii

    iiidefconiii Member

    Messages:
    106
    Hardware:
    32/64bit, +Arduino
    Could you please clarify like no you need an adapter or no you don't need an adapter xd
     
  13. siz

    siz New Member

    Messages:
    25
    Hardware:
    RPi2
    I have one adapter for the led going to 5v and ground at the start of my strip, then on the end of my strip 5v and ground are connected as shown in the picture (so 5v and gnd are looped on the strip).
     
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  14. iiidefconiii

    iiidefconiii Member

    Messages:
    106
    Hardware:
    32/64bit, +Arduino
    I never did this. Will do this soon thank you