<p>I want to run two stepper motors using Arduino Mega 2560 and RAMPS 1.4. But, somehow I burned the Arduino while I was connecting the motor and plugging the board to the computer.</p>
<p>Can I plug external power supply and USB connection to the computer at the same time?</p>
<h3>Additional info from comments</h3>
<p>I am using RAMPS 1.4 with Polulo red stepper drivers and Arduino Mega R3. I am only using two Nema 17 stepper motors and not using any hotbed or anything else other than the two stepper motors for the x and y axes. I am feeding 11.9 V supply to the RAMPS board. When powered on, can I plug the USB to my computer?</p>
<p>Suppose I have connected two motors on the X and Y outputs of the RAMPS, and the external power supply is on, then can I connect my Arduino to my PC using USB? Will it burn my board or not?</p>
<p>My only trouble is that when the board is on load, connecting the USB to computer motors would take power by Arduino pins instead of the RAMPS external supply.</p>

[{'answer_id': 5764, 'author': 'profesor79', 'author_id': 9730, 'author_profile': 'https://3dprinting.stackexchange.com/users/9730', 'pm_score': 0, 'selected': False, 'text': '<p>The answer is, yes you can, but you need to follow guidelines.</p>\n<p>Reversing +/- or otherwise incorrectly connecting power can destroy your electronics and cause fire hazard.</p>\n<hr />\n<p>From <a href="http://reprap.org/wiki/RAMPS_1.4" rel="nofollow noreferrer">RepRap wiki - RAMPS 1.4</a></p>\n<blockquote>\n<p>Maximum Input Voltage Power Supply without diode There are three\nlimiting factors to the maximum voltage that you can put into the\nRAMPS:</p>\n<p>The Arduino Mega maximum input voltage Filtering capacitor maximum\nvoltages PTC fuse maximum voltages First, the 1N4004 diode connects\nthe RAMPS input voltage to the Arduino Mega which has a recommended\nmaximum input voltage of 12 volts. If your board does not have this\ndiode soldered in (or if you cut it), you will need to power the Mega\nthrough the USB connector or through a separate 5v line, but this\nallows a higher RAMPS voltage.</p>\n<p>Second, most boards use 25v or 35v aluminum electrolytic capactors\n(C2, C3, C4, C6, C7, C9, and C10). To be safe, you should only go to\nhalf of your rated maximum voltage -- thus if your board has 35v\ncapacitors (code VZA) then you should use a maximum input of 17.5v.\nThe absolute maximum voltage is determined by the pololu servo\ndrivers, which themselves are limited to 35V.</p>\n<p>Third, the MF-R500 (5A) PTC fuse is rated to 30V and the MF-R1100\n(11A) PTC fuse is rated to 16V. They will need to be replaced with\nreal fuses.</p>\n<p>Power Supply with diode If your board has a 1N4004 diode soldered in,\ndo not apply more than 12 V to it. Original flavor Arduino Mega are\nrated to 12 V input. While Arduino Mega 2560 can take 20 V, it is not\nrecommended.</p>\n</blockquote>\n'}, {'answer_id': 5772, 'author': 'IanCaz', 'author_id': 10439, 'author_profile': 'https://3dprinting.stackexchange.com/users/10439', 'pm_score': 2, 'selected': True, 'text': "<p>I had a similar issue building my Prusa i3 Mk2s clone.  I was constantly hooking &amp; unhooking my Arduino from my PC while the printer was plugged into the mains.  At some point it had enough &amp; it released some &quot;magic smoke&quot;.  Later on I found out this was the power regulator on the Arduino.</p>\n<p>You shouldn't <strong>need</strong> to plug in the USB and the external power to the Arduino at the same time, but if you did, it is smart enough to only use one.</p>\n<p>That being said, by default the RAMPS passes 12V straight to the Arduino in order to power it (the Vin pin).</p>\n"}]
['https://3dprinting.stackexchange.com/questions/5762', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/10423/']