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Support Forum » Initial project fail

June 03, 2010
by keithka
keithka's Avatar

Got my kit today, wired up the first project. First time I attached the battery, the voltage regulator got hot, so I unplugged the battery. Then I realized I'd grounded pin 23 rather than pin 22, so I fixed that, but I promise everything else is right now. Anyway, when I connect the battery, the screen blinks about 4 times/second - no characters, just a bit of light from the whole screen.

My meter shows a steady 4.942v between the red & blue rails, so I'm inclined to say the battery & voltage regulator are good. What are the odds I fried the MCU in a few seconds of having pin 23 grounded instead of pin 22?

To make connecting things easier, I'm using about 6" wires between the display and the breadboard, but the picture shows much shorter wires in use. Maybe that lets a little more noise in, but surely it's not that sensitive. Or is it?

June 03, 2010
by keithka
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pictures here

Thanks in advance

June 03, 2010
by keithka
keithka's Avatar

Woo hoo! I'm in business. Operator error.

Constructive suggestion - the picture on page 29 of the PDF that shows how the pins are numbered on the LCD somehow left me with the impression that 14 is the last (leftmost in the picture) pin. Maybe it would help to have a comment that there are 16 pins total, and pins 15 and 16 aren't used.

June 03, 2010
by mongo
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Actually, 15 and 16 can be used. They are the backlight for the LCD. Because of the drain it adds to the power supply when using the 9V battery, it is suggested not to use it.

June 04, 2010
by hevans
(NerdKits Staff)

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Hi keithka,

Thanks for the suggestion. We will consider making that picture more clear in a future iteration of the guide. Glad you figured it out though. Hope you are enjoying your NerdKit!


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