Arduino + Ramps + LCD

Hello everyone.
I want to make my 3d priter to run without USB conenction, only with powering my power supply. However, when i connect power supply without usb in my pc, LCD just lights all its pixels and wont work.
It seems that arduino wont get needed 5 Volts. My diode D1 on RAMPS is installed. What is the solution without powering arduino with 5Volts externally? Thanks
BTW: my 5Volt regulator shows 3Volts

Edited 1 time(s). Last edit at 04/04/2016 07:35AM by Capinho.

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Capinho
BTW: my 5Volt regulator shows 3Volts

Sounds like the regulator is faulty then. You can replace it, replace the mega2560, or rig an external 5V reg and feed it into the 5v line. It would probably also be a good idea to figure out why the regulator got damaged. Usual reasons are drawing too much current on the 5V line, perhaps by running servos without external power, or providing more than 12V on the input side which means it has to dump more heat for any given amount of current.

My Kossel mini runs 4 stepper motors, 4 endstops no external servos or anything. It is powered up with 12V power supply.

The graphic LCD panel pushes the 5V limit on the Arduino's 5V regulator and often cooks the chip. Try replacing the regulator with a non surface mount package type like an L7805 and add a small heatsink.

The reason the regulator gets so hot is that it has to drop 7V from the 12V supply to produce 5V out. Whatever current the 5V part uses is about the current with the 7V, so the regulator heats up. The regulator actually burns up more power than the LCD uses.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

The problem is not the regulator.
I have the same display on a Ramps board.
When no USB is connected the ramps board does not get the 5V unless the Arduino is powered through the DC jack.
For some reason the Ramps board (at least my v1.4) needs the 5V for the display from somewhere.
Powering the Arduino through the Ramps works fine but does not provide the 5V on the pins for the display connector

Quote
Downunder35m
The problem is not the regulator.
I have the same display on a Ramps board.
When no USB is connected the ramps board does not get the 5V unless the Arduino is powered through the DC jack.
For some reason the Ramps board (at least my v1.4) needs the 5V for the display from somewhere.
Powering the Arduino through the Ramps works fine but does not provide the 5V on the pins for the display connector

There are versions of the ATMega that will run down to 1.8V with varying restrictions, so the fact that the arduino still runs doesn't prove much. Did you measure the output from the voltage regulator?

Edit: I missed that bit about it working when you supply power through the jack. That's odd, I thought the Ramps 12V -> d1 -> mega injected the power at the same point as the barrel jack.

Edited 1 time(s). Last edit at 04/04/2016 10:29AM by JamesK.

That was my though as well but when I measured there was nothing.
So adding power to the Arduino itself solved the troubles for good.
Not 100% if it is a general design bug or just on the china clones like the one I use.
But with a fix that easy I don't really bother dissecting the circuit board to find out what happend to the power supply.