Rambo

RAMBo

Release status: Development

Description	An all in one RAMPS class motherboard targeting convenience, reliability, and performance
License	GPL
Author	User:johnnyr
Contributors
Based-on	RAMPS
Categories	Electronics
CAD Models
External Link

Summary

RAMBo (RepRap Arduino-compatible Mother Board) is an all in one RAMPS class motherboard targeting convenience, reliability, and performance.

More info coming soon...

• 

  All connectors

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  Main connectors

• 

  Auxiliary connectors

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  Schematic

• 

  Top/1^st copper layer

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  Ground/2^nd copper layer

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  Supply/3^rd copper layer

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  Bottom/4^th copper layer

Features

Logic

• Arduino MEGA compatible Atmega2560 and Atmega32u2 processors are compatible with all RAMPS class firmwares
• Crystals for both usb and mcu (timing accurate to 10ppm)
• 4 Thermistor jacks
• All extra pins broken out on both processors (allows using the 32u2 for LUFA AVR programmer, etc.)
• 2 channel SDRAMPS compatible SPI breakout

Motor Drivers

• 5 A4984 1/8th microstep motor drivers (2 connectors on Z for Prusa Mendel)
• Digital Trimpot for stepper current control
• Current limit on driver IC VCC to prevent permanent latchup
• Microstep mode configured by MCU through firmware (no jumpers needed)
• Test points for driver control signals
• Step and Direction pins are on their own ports for synchronous movement capability
• Extra driver ports broke out for up to 3 additional drivers

PWM DC outputs (Extruders, Fans, Etc.)

• 5 outputs
• Low resistance mosfets for cool running
• Indicator led for each channel

Power

• Three independent power rails all accepting 10V-26V input voltage
  • Heated Bed 14A
  • Extruders 5A (fuse can be exchanged for up to 10A capacity)
  • Motors and logic 5A (fuse can be exchanged for up to 10A capacity)
• Built in SMPS for 5V generation from 10V-26V Vin

PCB

• 4 layer
• 2oz copper on all layers
• High quality, High temperature FR4-TG130 PCB
• Gold ENIG finishing

Source

Eagle board, schematic, and a printable pdf of the schematic. File:RAMBo.zip

Motor Current

The current for the stepper motors is set by firmware controlling the digipot. You can verify the max current for each driver by plugging the reference voltage (V_REF) measured at the X_REF test point (Y_REF,etc for the other drivers) in the following formula:

I_TripMAX = V_REF/0.8

This formula is from the Allegro datasheet : I_TripMAX = V_REF/(8 X R_S). R_S = 0.1, the value of the sense resistors.