I've been following adafruits RPi tutorials (and bought their starter kit)

I had an Sparkfun LCD Kit lying around. (It has an HD44780 controller LCD, a 10K trimpot and a 16 pin male header)

I soldered the header to the LCD, not all that well. I followed the tutorial step by step. This page has the wiring and I started bit by bit.

Symptoms : When I connected the trimpot and turned the knob a random bunch of boxes go dark and then they just slowly lighten and disappear. Even when it happens is intermittent. Sometimes I turn the knob, nothing happens, sometimes it lights a few boxes and on their own they dim out.

Below is what is looks like.

This is the schematic of the whole connection. I doubled checked it a couple times. Nonetheless I ran the code the show stuff on the LCD and it just blinks a little randomly.

  1. Is something wrong with the LCD? I messed the soldering?
  2. Is there a possibility of my connections being wrong?
  3. Could the trimpot be the wrong way in? (I tried both ways)

Could you help me narrow this down please?

LCD connected to Raspberry Pi

  • \$\begingroup\$ This sounds like a bad LCD... (to me, at least) \$\endgroup\$
    – apnorton
    Jun 22, 2013 at 19:50
  • \$\begingroup\$ @anorton ah, yea I'm a completely newbie here. If you think that is it then I will probably have to wait a day or so and try with a newer LCD :'( \$\endgroup\$
    – gideon
    Jun 22, 2013 at 19:52
  • \$\begingroup\$ Well... wait for another opinion first--I'm a complete newbie, too, to RasPi, but I do have experience with dying hardware... :) \$\endgroup\$
    – apnorton
    Jun 22, 2013 at 22:08
  • \$\begingroup\$ you could try connecting VO to 5.0v directly, this should give you the lowest brightness and you should see all the boxes... \$\endgroup\$
    – mux
    Jun 23, 2013 at 3:08
  • \$\begingroup\$ Quick check: Do you have the 3 Volt or the 5 Volt version of the LCD? The datasheet indicates that both types exist. \$\endgroup\$ Jun 23, 2013 at 7:03

1 Answer 1


Looks like a bad LCD. You can try resoldering your connections to the LCD, they look poorly done. The joints should look like this: http://smartduino.com/wp-content/uploads/2012/11/SMRTM501.jpg

See this guide for troubleshooting bad solder joints: http://learn.adafruit.com/adafruit-guide-excellent-soldering/common-problems

  • \$\begingroup\$ Thanks for your answer. Unfortunately I realized only while soldering that my soldering iron tip was just too bit for something like this. Half the time I ended up soldering two tips together. I'll get one of those fine tipped soldering irons and try again. \$\endgroup\$
    – gideon
    Jun 23, 2013 at 5:52

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