Can I plug Arduino Mega USB input (to supply power) and RAMPS 1.4 power input at the same time?

This is because when I plug the PSU into the RAMPS 1.4 alone, the LCD keeps restarting and it just gets stuck at the Marlin logo but if I plug the USB to the Arduino Mega alone, it works perfectly fine except the motor won't move (maybe not enough power) or maybe there is any other suggestions?

  • 1
    $\begingroup$ Considering the amount of questions and problems with the RAMPS shields, I'd advise you to buy a proper control board and a decent power supply. The RAMPS shields are pretty outdated nowadays. $\endgroup$
    – 0scar
    Commented Mar 8, 2022 at 17:41
  • $\begingroup$ Can you suggest the proper control board? $\endgroup$
    – Michael
    Commented Mar 8, 2022 at 18:16
  • $\begingroup$ Any 32-bit board, look at the BTT SKR boards. $\endgroup$
    – 0scar
    Commented Mar 8, 2022 at 19:02
  • $\begingroup$ "any other suggestions?" - Disconnect the heated bed (in order to reduce the current draw) and hopefully that will solve the immediate issue. Then use your second PSU to power the heated bed separately, using an external MOSFET, as per this previous answer. You shouldn't need to provide a separate USB power supply once you have done that. $\endgroup$
    – Greenonline
    Commented Mar 9, 2022 at 6:29
  • $\begingroup$ But I didnt install any heated bed. $\endgroup$
    – Michael
    Commented Mar 9, 2022 at 7:00

1 Answer 1


Yes you can, that is the purpose of diode D1 on the RAMPS board.

It should be noted that if the RAMPS 1.4 does not have diode D1 then the Mega2560 will/can not be powered via the RAMPS board and it is necessary to power the Mega2560 separately, for example via the USB.

See Power for the Arduino Mega board on the RAMPS 1.4 RepRapWiki page:

Power for the Arduino Mega board

The RAMPS 1.4 has a 1N4004 diode labeled D1 which allows 12V to feed and power the Arduino Mega 2560 board. This diode is installed in most pre-assemble boards, thus the Arduino board is powered by the Ramps by default.

When the RAMPS is not powered or if the diode is not installed or cut/removed, the Arduino gets its power from USB or a power supply connected to its 2.1mm (center positive) power jack.

The Arduino provides a Vin connection to connect an external power source that can be from 7V to 12V, remember the diode D1 can not be connected if you plan to power the Arduino using its Vin.

Where to find the D1 diode (note that D2 is shown at the left, not

The Arduino Mega is not rated for voltages higher than 12V. If your board has a 1N4004 diode soldered in Diode D1 (which is the case with most assembled board), do not apply more than 12V in the 5A connector of your Ramps, refer to RAMPS 24v for more information.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .