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I have a Mega 2560 with a ramps 1.4 shield. I noticed when I turn on the 14v power supply the mega would also power up and run.

Am I damaging it running it at 14v? If not is there a solder or jumper somewhere that I can set it to only run the mega/logic on the usb power? The 14v is just for the stepper motors.

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    Input Voltage (limit) 6-20V
    – Gerben
    Commented Dec 17, 2015 at 19:32
  • reprap.org/wiki/RAMPS_1.4#Power_Supply
    – Mikael Patel
    Commented Dec 17, 2015 at 20:30
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    Where is the 14v being supplied to? You Seem surprised that it's receiving power this way, so I assume it's not through the 'usual' channels. I'm not familiar with the board, but as above, it will run on 14V, just make sure they are going into the correct hole!
    – MalphasWats
    Commented Dec 17, 2015 at 22:06
  • @MikaelPatel If your board does not have this diode soldered in (or if you cut it), you will need to power the Mega through the USB connector or through a separate 5v line I read that page but missed this sentence! I'll always have usb power (To push gcode) so that looks like the answer.
    – asawyer
    Commented Dec 17, 2015 at 22:24

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You can, but you shouldn't, because the the board will heat excessively, as you're out of the recommended range for the input voltage on vin (7-12V).

Unless you have a switching regulator (the one on the board is linear), then you shouldn't' have too much of a difference between the operating voltage and vin as an operating principle because of efficiency (and thus heat) issues.

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  • Thanks! It looks like I can remove a diode on the ramps board to stop it from supplying power to the mega and that will solve the problem completely.
    – asawyer
    Commented Dec 17, 2015 at 22:25
  • Incidentally, most of the cheap barrel jack sockets you can get, like the one on the Arduino boards, are only rated for 12V maximum. That, more than the regulator's heat dissipation, is the limiting factor.
    – Majenko
    Commented Dec 18, 2015 at 0:22

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