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From what I've seen of articles and videos online, everyone seems to be using the 3.3V GPIO pin. I have an LCD screen which requires a 5V power supply and I wondered whether it would be safe to use the Raspberry Pi's 5V GPIO pin? If you can't use it, what is it there for?

I have a 16x2 KS0066 (apparently compatible with HD44780) LCD screen Picture of LCD screen

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    As long as the LCD does not need more than 200ma (assuming you are using 1A supply on model B) then you are fine to use it as supply. Model B can peak at 800ma so 200ma is safe to use as spare from the 5V Pin. If you need more use another power supply/board to connect direct to the power supply if it is more than 1A – Piotr Kula Aug 20 '12 at 15:21
  • I bought this before I knew what I was doing: oomlout.co.uk/lcd-display-16-x-2-p-212.html The technical specifications seem to indicate it will draw 1.2mA@5V. – Mark Ingram Aug 21 '12 at 7:32
  • I think the 5V pin gives you less than 5V because it is subject to use by other resources, however the 3V3 is consistently 3V3. I am not with my Pi until weekend but use a multimeter (if you have one) and you will see you don't get the full 5V. – AnthonyBlake Aug 21 '12 at 9:06
  • @AnthonyBlake because the 5V is not regulated on pcb but supplied by external power. 3v3 is regulated from the 5V rail. A slight voltage drop will not affect this LCD screen. – Piotr Kula Aug 21 '12 at 9:57
  • @ppumkin ah okay, I am quite new to electronics so I didnt know if that would have an effect. – AnthonyBlake Aug 21 '12 at 10:09
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There is a brilliant tutorial at Adafruit how to connect a 16x2 LCD to the Raspberry Pi using the 6 I/O pins.

enter image description here

As this is just a small LCD screen and you said in your comments it only uses 1.2mA you will be perfectly fine to use the +5V GPIO Pin to power the LCD .

When you want to use more peripherals though you would have to look into using an I2C interface instead.

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    the link works perfectly fine for raspberry pi model b 2 if all the pins are correctly configured. Thanks @ppumkin – ravi.zombie Jan 18 '16 at 8:47
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Go for it! You should, of course, look at the schematic and note their is a 1A fuse on the supply; depending on your USB peripherals you will be limited to between 200 - 500mA. If this is not enough, you could power the Raspberry Pi via the 5V pin.

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It should be fine. The backlight is the main power user, and it's typically only 20mA in addition to the 1mA that the LCD part uses.

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