External 5v power supply for Ramps.

I've been reading that the 5v outputs on the ramps board is powered from the arduino, and if I use a 12864 LCD it will probably damage the voltage regulator on the mega.

So if I have an external 5v power supply(atx psu), how do I replace the 5V that comes from the arduino with the 5V that comes from the psu?

PS: I still want ramps supplying the Arduíno with 12v, I just don't want ramps to get the 5v from the mega, which will cause it to overheat.

Edited 1 time(s). Last edit at 12/05/2017 05:17PM by vitorbrazil.

Not sure if that's someones theory or what, I ran my 12864 off my ramps with no mods for many months before the ramps power connector fried.
My original mega is still fine and I could have just replaced the ramps but I had an MKS Gen 1.4 in the drawer so I started using that instead.

"PS: I still want ramps supplying the Arduíno with 12v, I just don't want ramps to get the 5v from the mega, which will cause it to overheat."

Thats seem somewhat silly.

The 12v on the ramps is feed to the mega where it is directly connected into the voltage regulator which generates the 5v
The mega doesnt use 12v anywhere else

So remove D1, and apply you 5v supply to any vcc pin and gnd from your supply to gnd on the ramps (an unused endstop is good for this)

But if you insist

I would cut the 5v line between aux1 and aux2 and apply 5v and gnd to the 5v and gnd pins on aux2
(this powers the SPI 5v and AUX4 5v lines from a separate supply)


You can see the 5v track on the front of the PCB along the he bottom right of this picture

Edited 1 time(s). Last edit at 12/05/2017 07:01PM by Dust.

Pardon my ignorance, so if I cut the D1 pin, and apply the 5v supply(5v and ground) to any vcc pin and gnd on the ramps, it will supply the entire 5v rail on the ramps board and also provide 5v for the arduino without going through the voltage regulator?

D1 as in diode 1 (under the X and Y pololu modules) you need to remove that (or just cut one leg of the diode)


Other wise yes. That will deactivate the mega voltage regulator and use your 5v for all 5v on ramps and mega.

That's perfect, exactly what I need , last question, if I do this, can I connect the arduino usb to my pc while it is being powered from the 5v pin?

By the way, vcc is any 5V, right? Can I connect like in the image (vcc and gnd or 5v and gnd)?

Edited 2 time(s). Last edit at 12/06/2017 10:32AM by vitorbrazil.

The board has some bad labeling...

the 3 pin next to reset says vcc, 5v and ps-on. but the 5v is only to power the 5v line of the servo pins, ie you can't use that. Similarly you can't use the 5v pins on the servo plugs as it doesn't tie into the main 5v. (this can be changed by putting a jumper from vcc to +5v, which is what the 3 pin connector is for)


most other pins 5v and vcc are interchangeable

yes you can use all you have outlined.

What would happen if I just connected the 5v supply to ramps without removing D1?

then the voltage regulator and the new supply will fight each other, The fractionally lower one (since two identical supply's is unlikely) will get back fed the difference. That supply will be unhappy with this, either heating up or dying

After doing this, can I connect usb while having the power supply on a 5v pin?