Ramps 1.4 keep resetting after installing 2 stepper driver or more (7 replies)

I have marlin fw running but after I install 3 stepper driver my screen start getting dimmer. But after I install the last one my ramps 1.4 keep resetting. But after I remove all the driver it behave normal again. Also one more thing. When I only connect 12v nothing happen but I can power it with usb.

Please help me. Thanks a lot.

Karl