LCD screen gets hot and sucks power from Raspberry Pi

connectorlcdmicrocontrollerpowerraspberry pi

Has anyone else experienced LCD screens overheating, and drawing too much current? I was trying a GPIO project with my Raspberry Pi in an attempt to interface with an LCD screen but for some reason my PI's OS shuts down while the black dots on the back quickly begins to boil (I'm guessing these black dots are heat sinks), and on top of that no characters display (thanks to my Pi being knocked out).

I know my pinouts are all correct as I used another LCD that worked great. I'm using two of the generic Hitachi HD44780s for this project, but they're from different kits.

Project tutorial I followed for both screens:

http://www.rpiblog.com/2012/11/interfacing-16×2-lcd-with-raspberry-pi.html

NOTE:
This happens when I connect my ribbon cable up to the Pi (the ribbon cable facilitates the wiring for the GPS), otherwise I can't start my Pi. What I've been doing is starting with my ribbon cable disconnected, boot up, and then I try plugging everything back into my Pi. Of course this just leads to the power being sucked up, crashing everything, and heating up the LCD. I'm also not powering the backlight, so that doesn't seem to be source of the problem.

Do I just have a broken LCD?

Best Answer

It's hard to tell from your description (well-focused, properly cropped, well-lit photos would help) but ...

The "black dots on the back" are probably "Chip on board" (COB) packaging of an LCD controller IC. If that's heating up to near 100C ("boiling), you certainly have problems and are at or beyond the point of permanent damage.

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Photo©MikroLogika enter image description here
Photo©RedGrittyBrick

As I said in a comment, my best guess (and it's a guess because there is insufficient information for anyone to know the answer) is

  • You haven't wired up your circuit correctly and/or
  • The diagram you are following is incorrect and/or
  • Your module isn't like the one in the tutorial you are following.

These type of LCD module come in 3.3V and 5V variants. The tutorial you are following is drawing power from the Pi's 5V pin and is for a 5V module. Maybe your LCD module is a 3.3V variant. In which case it should not be connected to the Pi's 5V power pin.

Note: "The maximum permitted current draw from the [Raspberry Pi's] 3.3 V pin is 50 mA."

If you look at a datasheet for an example 3.3V LCD module you'll see that it claims a supply current (IDD) of 2.5 milliamps, the backlight current (ILED) is 19 millamps (mA) So if you are measuring over 1000 mA (1 A) - something is very very wrong.

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