How do I wire external 5v for servo?

I have a ramps1.4/mega2560 and I have come to the conclusion that my bltouch(generic made by geeetech) is drawing more amps than the mega board can put out because when the probe deploys it makes the LCD flicker and thermistor readings go all over the place. I am going to use a step down converter from a 12v power supply but I don't know how to safely do this. Do I need any type of current limiting device ,resisters, etc., in between? can I just hook the positive straight up to the vcc jumper pin? Also, where exactly do I hook these up to? Do I put the positive on the VCC and just hook the ground anywhere on the servo pin ground?

Quote
Todd900
. Do I need any type of current limiting device ,resisters, etc., in between? can I just hook the positive straight up to the vcc jumper pin? Also, where exactly do I hook these up to? Do I put the positive on the VCC and just hook the ground anywhere on the servo pin ground?

Noting inbetween. Positive of the converter just to the sensor; don't connect it to the 5V on the board. Ground can be anywhere; these buck converters have a common ground, so it's the same ground your ramps and atmega uses.
Other option is using the output to drive your atmega and ramps; D1 on the ramps has to be removed for this, and i think a connetion heas to be made from atmega's 5 volt out to the atmega 5v in.