hello, so I'm using a Ramps 1.4 with an Arduino Mega 2560. When I plug the usb in Arduino, the lcd works perfectly, but if I use an external Power Supply, the LCD starts working in low contrast; I already measured the LCD's output voltage and I measured 5v in one pin but the other one I measured 0,09 V on its pin. I already tried changing the flat cable, the Arduino and even the Ramps 1.4 and still nothing works. Can someone help me please? (sorry for my bad english, I'm still learning)
Your topic does not indicate a problem with IDE 1.x and hence has been moved to a more suitable location on the forum.
1 Like
That calls for schematics. There's a hardware/wiring mistake somewhere.
This is actually a common voltage issue with the LCD. When operating it on a USB cable, you're only supplying about 4.5V due to the Arduino’s internal protection circuitry. However, when using an external power supply, the LCD gets the full 5V (or sometimes a bit more). This voltage difference can have a significant impact on the display contrast, which is normal.
The fix is simple: use a screwdriver to adjust the contrast potentiometer. If you plan on using both power sources, you’ll need to find a compromise setting that works for both voltage levels
I tried to adjust the contrast potentiometer but it didn't work.
At this point you need to post an annotated schematic showing exactly how you wired it. Be sure to include links to technical information on each of the hardware devices.
This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.