16 X 2 LCD W/ KEYPAD FOR ARDUINO

Modification needed before use

I ordered two of these for some projects where I need a display and some simple inputs.

I opened one and tried it with the sample LCD code in the Arduino IDE. Backlight came on and it appeared to be working. I couldn't see any text though. So I adjusted the contrast trimmer pot, which I thought was freely spinning (it wasn't), but that led me to a post about some faulty designs on this type of 16x2 LCD shield.

Someone wrote a sketch to test if the backlight circuit was a faulty design -- and these shields fail that test. I had to desolder the LCD board from the shield and then cut a trace between Pin 10 and the transistor under the LCD (and add a 510-ohm to reconnect the pin to the transistor).

Without this modification, you can burn out pin 10 on the Arduino, if the pin is set a certain way, as the transistor will pull too much current from the pin in certain states. Post to explain the issue:

https://forum.arduino.cc/index.php?topic=96747.0