Question Raspberry Pi Console Power/Battery help

Discussion in 'Handhelds' started by Tech Flare, May 11, 2018.

  1. Tech Flare .

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    Okay so I am building a portable Raspberry Pi console, and my goal is to make it as close to the Nintendo Switch in form factor and function as possible. I've been thinking about how I want to go about this and I have come to a few conclusions:

    I'm going to use a 7" screen that runs on 12 volts (although I think it can run at as low as 3.7 volts)
    I'm going to use Linux Joystick Mapper to map two 'VR Controllers' into one controller so I can put one on each side
    I'm going to use Retropie to run the games

    My only problem is how to set up the battery circuit. The Raspberry Pi takes micro-usb for power, while my screen takes a DC plug for power. I tried hooking up a LiPo battery to an Adafruit PowerBoost 1000c and then running wires from the LiPo plug on the PowerBoost to the screen, but that fried the PowerBoost.

    So that's where I am at. I'm not very good with battery circuits, so any help will be appreciated.
     
  2. Stitches 2 and a Half Dollarydoos Staff Member . . .

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    "from the LiPo plug on the PowerBoost to the screen" I'm going to give you the benefit of the doubt and assume you meant to write: "from the output plug on the PowerBoost", and didn't just run wires straight from the battery input terminal to the screen.

    As for your problem, we need more info. Like:
    • What capacity is the lipo?
    • Where did you buy it from?
    • Was the lipo fully charged?
    • Are you sure the PowerBoost is legit?
    • Photo of your wiring please.
    • Model of your screen and where you got it from.
    • What gauge wire are you using?
    • Have you (carefully) probed the screen's driver board with a multimeter to find its 5v reg?
    • What specific Raspberry pi model are you using?
    • Photo of your wiring please.
     
  3. Tech Flare .

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    here are the answers to your questions:
    • My lipo battery has 3.7 volts.
    • I bought the lipo from Adafruit.com.
    • yes, I charged the lipo
    • yes i bought the powerboost from Adafruit.com
    • The powerboost was fried in the process, so i desoldered the wires. (With all due respect, my question was about a new solution to power my screen and raspberry pi. I don't see how this is relevant.)
    • I bought the screen off of Ebay. Model #QC750BG1
    • I used generic jumper wires with the tips removed. (probably not the best idea but its all i had)
    • The screen's driver board is labeled very well, so I didn't need to. (the screen only has 12 volt pins but when i soldered the 3.7 volt battery to it the screen still worked fine.)
    • I am using a Raspberry Pi 3 model B v1.2
    • again, i desoldered all my wires because the powerboost is fried.
    hopefully this answers your questions! Sorry it took so long.
     
  4. Stitches 2 and a Half Dollarydoos Staff Member . . .

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    Capacity mate, not voltage. The capacity of a cell is the number with "mAh" at the end, 2500mAh for example. You also didn't specify how to wired the powerboost to the screen. Did you wire the screen to the output pins of the Powerboost, or the battery input terminal?
    This is the model number of the LCD panel only, what driver board are you using with it? Can you post a photo of the board and panel?

    As for the Powerboost frying itself, it's possible that the driver board was drawing too much power from you undervolting the 12v line. These boards normally step the 12v input down to 5v, and then down again from 5v to 3.3v and 1.8v. Depending on the cheap 5v step down reg they put on that board, it's possible that it didn't like being fed such a low voltage. This could possibly lead to overdraw, which the Powerboost is supposed to be protected from, or perhaps even an internal short. That's the only thing I can think of. If you use a 12v supply to run the screen and board, there should be a number of 8 legged ICs on the board. If you check them with a multimeter you should find that one of them will have a leg that outputs between 4.5v and 5.2v. If you lift that leg off the board and solder a 5v carrying wire to the pad, that should run the screen with significantly less power.

    Unless you want to design and assemble a custom PCB using a 5v step up reg with a higher output current, I'm afraid the Powerboosts are your only safe option. ("safe" being relative to correct operation)
     

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