Arduino 5V regulator dies just by unplugging the USB cable?

Genuine Arduino Mega 2560 and RAMPS 1.4.
The PSU was on and the USB cable was plugged in. However, the pc failed to recognize the Arduino (which happens sometimes), so I wanted to unplug the usb cable and plug it in again. When unplugging the usb cable I heard a quiet bang and the LCD went out. Now the LCD does not work when the PSU is on. If I connect the USB cable, the display lights up but is not very bright.

If I plug in the cable, turn on the heated bed and hot end, the display gets even dimmer (0,3V voltage drop when turning on all heaters). So this means that when the USB is connected the 5V regulator probably kinda works because the display brightness changes when the input voltage changes. However, without USB the LCD is completely dark....

I am probably going to buy a cheap arduino clone and replace it but I am still trying to find out what went wrong.. How did I manage to fry an Arduino by unplugging it?

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Self-sourced Mendelmax 2.0-based Reprap Machine -- Ramps 1.4 & Mega 2560 -- DRV8825 (Z@1A, [email protected], [email protected], E@1A) -- genuine E3D v6 direct setup -- 350W custom silicone heated bed -- ABS 1,75mm -- Marlin 1.1.0-RC7 -- Cura 15.04.6

The load on the 5vdc regulator on the Mega was too much and it finally did a rapid release of the magic smoke when you unplugged the usb. The LCD puts the current load on the Mega at or above it's limit.


When the LCD setup was first released, the adapter had a voltage regulator on it and used AUX1. When it was copied, that regulator and AUX1 use was eliminated.

As stephenrc says. See #1 at [reprap.org].

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Cant the 5V side be supplied by the 5V rails on ATX supplies? I seem to have escaped this problem so far, but when i got second arduino/ramps I noticed it wouldnt work from 12v alone, I never noticed on the other as its always connected to PC, hopefully I can free the chains with a better board in future.

Quote
MechaBits
Cant the 5V side be supplied by the 5V rails on ATX supplies?

Yes, if you are using an ATX supply then you can do that. There is a diode on RAMPS that you can remove to prevent it feeding 12V to the Arduino's 5V regulator.

Edited 1 time(s). Last edit at 07/13/2016 03:24AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

There is one thing which is still unclear to me. The voltage regulator is only needed when there is no external 5V power source (through the 5V input or usb). However, I had the usb cable almost constantly plugged in, so the 5v regulator wasn't supposed to overheat...

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Self-sourced Mendelmax 2.0-based Reprap Machine -- Ramps 1.4 & Mega 2560 -- DRV8825 (Z@1A, [email protected], [email protected], E@1A) -- genuine E3D v6 direct setup -- 350W custom silicone heated bed -- ABS 1,75mm -- Marlin 1.1.0-RC7 -- Cura 15.04.6

...and one more question: Could I replace the AMS1117 5.0 with something more... durable?

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Self-sourced Mendelmax 2.0-based Reprap Machine -- Ramps 1.4 & Mega 2560 -- DRV8825 (Z@1A, [email protected], [email protected], E@1A) -- genuine E3D v6 direct setup -- 350W custom silicone heated bed -- ABS 1,75mm -- Marlin 1.1.0-RC7 -- Cura 15.04.6