High Power Pololu Board (Powerlolu) based on A4989 - can be connected to RAMPS Pololu port. Powerlolu can drive stepper motors up to 500 Watts, drawing currents up to 10 Amps. The existing Pololu boards found in common RepRap 3D printers are at their limits when driving the 2 Nema17 z-axis stepper motors in parallel. Continuous z-axis movement can cause the board to overheat. These boards hardly drive stepper motors bigger than a Nema17. To avoid overheating or to drive larger motors a more powerful driver board is needed. The Powerlolu board enables the use of bigger stepper motors for a wide range of uses. This could be the conversion of manual milling machines into computer controlled milling machines (CNC-Machines) using the affordable electronics such as Arduino and RAMPS. Building 3D printers with a larger print volume or with larger extruders would be possible. Tested the design by connecting a Nema43 stepper motor by Nanotec Electronic (capable of 6.6 Amps per coil, Torque 2000Ncm, Weight 8,4kg) to a Powerlolu attached to a 3D printer's RAMPS X-port. A short video of the new driver can be seen on YouTube at https://www.youtube.com/watch?v=G9FWvhZI7rs . After two hours of motor usage the Powerlolu board only got luke warm - however see installation note below The schematics for the Powerlolu driver are freely available at https://github.com/fluidfred/powerlolu. Technical specifications: 3-wire control with DIR, STEP, Enable-signal, compatible to the Pololu board Supply voltage of the stepper motor from 12V to 50V Adjustable stepping via SMD-jumper, 1, 1/2, 1/4, 1/16 (default) steps Precision pot to adjust the current limiter no extra heat sink required due to passive cooling, up to NEMA 23 connected Molex snap-on connector for connecting the RAMPS board to the Powerlolu Important installation note: Observe the heat emission when using stepper motors larger than NEMA 23. If necessary, implement a cooling system, i.e. heat sinks mounted at the power-Mosfets and a fan. Each individual Powerlolu should be protected by connecting an appropriate fuse between VBB (X2) and the power source of the stepper motor. More installation notes can be found under http://wiki.germanreprap.com/en/handbuch/powerlolu concerning wiring with RAMPS and current limiter adjustment. There is a adapter board between powerlolu and RAMPS at github see: https://github.com/fluidfred/powerlolu/blob/master/Powerlolu_Pololu.brd