The new Arduino ADK is a microcontroller board which makes a great controller board for RepRap.

The Arduino ADK is a microcontroller board based on the ATmega2560 (datasheet). It has a USB host interface to connect with Android based phones, based on the MAX3421e IC. It has 54 digital input/output pins (of which 14 can be used as PWM outputs), 16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button.

The ADK is based on the  Arduino MEGA 2560.

Similar to the Mega 2560, it features an Atmega8U2 programmed as a USB-to-serial converter.

For information on using the board with the Android OS, see Google's ADK documentation.

Summary

More information at the Arduino page here.

Kit includes Pololu A4988 Stepper Driver w/ 1x16-pin breakaway 0.1" male header and Heat Sink 6.3mm X 4.8mm w/ adhesive tape.  Header & heatsink can be pre-assembled for an additional fee.

The A4988 stepper motor driver carrier is a breakout board for Allegro’s easy-to-use A4988 microstepping bipolar stepper motor driver and is a drop-in replacement for the A4983 stepper motor driver carrier. The driver features adjustable current limiting, overcurrent protection, and five different microstep resolutions. It operates from 8 – 35 V and can deliver up to 2 A per coil.

Note: This board is a drop-in replacement for the original Pololu  A4983 stepper motor driver carrier. The newer A4988 offers overcurrent protection and has an internal 100k pull-down on the MS1 microstep selection pin, but it is otherwise virtually identical to the A4983.

The A4988 stepper motor driver carrier is a breakout board for Allegro’s easy-to-use A4988 microstepping bipolar stepper motor driver. The driver features adjustable current limiting and five different microstep resolutions. The driver operates from 8 – 35 V and can deliver up to 2 A per coil.

• Simple step and direction control interface
• Five different step resolutions: full-step, half-step, quarter-step, eighth-step, and sixteenth-step
• Adjustable current control lets you set the maximum current output with a potentiometer
• Intelligent chopping control that automatically selects the correct current decay mode (fast decay or slow decay)
• Over-temperature thermal shutdown, under-voltage lockout, and crossover-current protection
• Short-to-ground and shorted-load protection

The A4988 stepper motor driver carrier comes with one 1x16-pin breakaway 0.1" male header. The headers can be soldered in for use with solderless breadboards or 0.1" female connectors.

Using the driver

Power connections

The driver requires a logic supply voltage (3 – 5.5 V) to be connected across the VDD and GND pins and a motor supply voltage of (8 – 35 V) to be connected across VMOT and GND. These supplies should have appropriate decoupling capacitors close to the board, and they should be capable of delivering the expected currents (peaks up to 4 A for the motor supply).

Step (and microstep) size

Stepper motors typically have a step size specification (e.g. 1.8° or 200 steps per revolution), which applies to full steps. A microstepping driver such as the A4988 allows higher resolutions by allowing intermediate step locations, which are achieved by energizing the coils with intermediate current levels. For instance, driving a motor in quarter-step mode will give the 200-step-per-revolution motor 800 microsteps per revolution by using four different current levels.

The resolution (step size) selector inputs (MS1, MS2, MS3) enable selection from the five step resolutions according to the table below. MS2 and MS3 have internal 100kΩ pull-down resistors, but MS1 does not, so it must be connected externally. For the microstep modes to function correctly, the current limit must be set low enough (see below) so that current limiting gets enganged. Otherwise, the intermediate current levels will not be correctly maintained, and the motor will effectively operate in a full-step mode.

Control inputs

Each pulse to the STEP input corresponds to one microstep of the stepper motor in the direction selected by the DIR pin. The chip has three different inputs for controlling its many power states: RST, SLP, and EN.  Please note that the RST pin is floating; if you are not using the pin, you can connect it to the adjacent SLP pin on the PCB.

Current limiting

To achieve high step rates, the motor supply is typically much higher than would be permissible without active current limiting. For instance, a typical stepper motor might have a maximum current rating of 1 A with a 5Ω coil resistance, which would indicate a maximum motor supply of 5 V. Using such a motor with 12 V would allow higher step rates, but the current must actively be limited to under 1 A to prevent damage to the motor.

The A4988 supports such active current limiting, and the trimmer potentiometer on the board can be used to set the current limit. One way to set the current limit is to put the driver into full-step mode and to measure the coil current without clocking the STEP input. The measured current will be 0.7 times the current limit (since both coils are always on and limited to 70% in full-step mode). Please note that the current limit is dependent on the Vdd voltage.

Another way to set the current limit is to measure the voltage on the “ref” pin and to calculate the resulting current limit (the current sense resistors are 0.05Ω). The ref pin voltage is accessible on a via that is circled on the bottom silkscreen of the circuit board. See the A4988 datasheet for more information.

Power dissipation considerations

The A4988 driver IC has a maximum current rating of 2 A per coil, but the chip by itself will overheat at lower currents. The actual current you can deliver depends on how well you can keep the stepper motor driver cool. The carrier’s printed circuit board is designed to draw heat out of the A4988 chip, but to supply more than approximately 1 A per coil, a heat sink is required.

Please note that measuring the current draw at the power supply does not necessarily provide an accurate measure of the coil current. Since the input voltage to the driver can be significantly higher than the coil voltage, the measured current on the power supply can be quite a bit lower than the coil current (the driver and coil basically act like a switching step-down power supply). Also, if the supply voltage is very high compared to what the motor needs to achieve the set current, the duty cycle will be very low, which also leads to significant differences between average and RMS currents.

More information on Pololu electronics at Pololu and RepRap.

Heat Sink 6.3mm X 4.8mm

Adding this PCB to your printing platform will transform it into a heated surface perfect for minimizing warping of larger prints as well as eliminating the need for a raft when printing with ABS.

• Dimensions:  214 x 214mm
• Print Area Dimensions:  200 x 200mm
• Includes: 1.8kohm 125mW 1% SMT resistor (x1)
• Includes: Red SMT LED (x2)

Mounting

The platform has a 3mm hole in every corner for using M3 bolts, other people may glue or clamp metal disks on the corners and use magnets. However, it has to be mounted on a heat resistant underground. An insulating material below the heatbed is highly recommended.

Heating element

The heating element is on the bottom side. The heating is done by long traces of copper.

The top side is solid copper to keep the PCB flat enough. Also it prevents that the print head can render the heatbed completely useless when accidentally crashing into it.

Printing

You will need some Polyimide Tape to have a surface that sticks to ABS plastic when hot.

When having this PCB covered with Polyimide Tape you will be able to print most objects raft-less on it. Please note that some smaller objects may become more difficult to print as the lower layers won't cool as fast as on non-heated beds. Printing multiple objects at the same time helps in this matter.

Ratings

With 12V, our prototype draws 9.9A when cold which goes down to 7.5A when hot. With isolation on the bottom of this heater, it reaches 100°C in about ~4,5 minutes, measured on the side of the heat field. These ratings may be slightly different on each PCB.

The base material of this PCB can withstand 150°C. However, a maximum of 120°C long time is recommended.

Connection

While the PCB is almost fully covered in a nice red solder resist, there are two connections to solder cables on. Also, a possibility to mount two SMD LEDS and one SDM resistor.

Important: Use only cables which can withstand at least 15A and are able to withstand the heat. Most silicone and PTFE covered cables should do.

Important: Be sure to cover the solder joints with insulating heat resistant tape (for example Polyimide Tape)

This heated bed is a product of reprapsource.com

RepRap.org page for this heated bed.

Overview:

The Arduino Mini is a small microcontroller board based on the ATmega328, intended for use on breadboards and when space is at a premium. It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 8 analog inputs, and a 16 MHz crystal oscillator. It can be programmed with the Mini USB adapter or other USB or RS232 to TTL serial adapter.

Specifications:

• Microcontroller:  ATmega328
• Operating Voltage:  5V
• Input Voltage:  7-9 V*
• Digital I/O Pins:  14 (of which 6 provide PWM output)
• Analog Input Pins:  8 (of which 4 are broken out onto pins)
• DC Current per I/O Pin:  40 mA
• Flash Memory:  32 KB (of which 2 KB used by bootloader)
• SRAM:  1 KB
• EEPROM:  1 KB
• Clock Speed:  16 MHz
• Dimensions:  30 x 18mm
  

*(Warning: Don't power the Arduino mini with more than 9 volts, or plug the power in backwards: you'll probably kill it.)