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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-16x2-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?

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  • \$\begingroup\$ After a quick look I'd try removing pins 15 & 16 from the LCD (backlight) for a start - they can draw significant current and trying to drive one from an I/O line looks dodgy to me. It probably varies by module but most I've used need a current limit resistor as well (just like a LED). \$\endgroup\$ – PeterJ Aug 14 '13 at 14:52
  • \$\begingroup\$ Tried that before, I'm going to update my situation because it's really acting up. \$\endgroup\$ – Monte Carlo Aug 14 '13 at 15:05
  • \$\begingroup\$ You have a miswiring problem and/or you are overloading the power supply. Have you tried measuring current draw? \$\endgroup\$ – RedGrittyBrick Aug 14 '13 at 16:05
  • \$\begingroup\$ Monte Carlo Unrelated to this question - see this question and answer \$\endgroup\$ – Russell McMahon Jan 7 '14 at 2:46
  • \$\begingroup\$ @Russel McMahon Thank you so much! Previous comment on my original question claimed that lack of information would have closed my question. So I decided to prematurely clean up after myself. \$\endgroup\$ – Monte Carlo Jan 7 '14 at 3:15
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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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  • \$\begingroup\$ When I set my multimeter to the 10 A setting I get a reading a 1.03, is that 1 or 10 amps? Does that help with your comment? Also, those are the same black dots on the back. \$\endgroup\$ – Monte Carlo Aug 14 '13 at 16:25
  • \$\begingroup\$ That would be about an amp, which is much more power than this should be drawing, and way more than you should be trying to pass to anything through the pi. Something is clearly wrong. But even once you find and fix the problem, you probably don't want to power this through the pi. \$\endgroup\$ – Chris Stratton Aug 14 '13 at 16:42
  • \$\begingroup\$ @Monte: See last part of updated answer. \$\endgroup\$ – RedGrittyBrick Aug 14 '13 at 17:35

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