Build instructions

Motor Connections

Unipolar

The Unipolar motor connection is straight forward because both the motor and the ULN2003 board usually come with a JST-XH connector. But nevertheless the table bellow lists the correct connections between the two components.

Remember to enable #define MOTOR1_USE_ULN2003_DRIVER on your config.h file, for more information check the firmware page.

Bipolar

Bipolar stepper motors are only supported by Ardufocus when using a step stick, due to the multiple motors and connectors available on the market it’s hard to specify which one will be the correct one in use at your configuration but nevertheless there are some tricks that will ease your job finding the correct connections.

NEMA17

All NEMA motors have only four wires, to find the correct windings just grab your multimeter and set it for resistance measurement. Label each one of the wires from 1 to 4 and then take any random two and measure the resistance between them, either you’ll get a reading or a open circuit. Keep measuring different wires until you get the two pairs that give you a reading between them and that’s your two coils.

Let’s assume wire 1 and 3 form a pair and 2 and 4 form the other pair, to connect it to the step stick connect wire 1 to 2B, wire 3 to 2A, wire 2 to 1B and wire 4 to 1A.

28BYJ-48

The table bellow shows the connections between the 28BYJ-48 motor and the A4988 step stick.

Remember to enable #define MOTOR1_USE_A4988_DRIVER or #define MOTOR1_USE_DRV8825_DRIVER on your config.h file, for more information check the firmware page.

Breadboard

28BYJ-48 with ULN2003 driver

This build is the cheapest focuser you can have not only due it’s bare bones approach but also due to the it’s minimal BOM, part count and availability of each item. Use this configuration only with unmodded 28BYJ-48 stepper motors.

BOM

Check the required BOM on the table bellow. The 100nF capacitor is only required if you intend to use Ardufocus in a Moonlite compatibility mode i.e. use Moonlite’s ASCOM drivers, if you intend to use Ardufocus ASCOM drivers then this capacitor is not required.

Settings

Edit your config.h file and set make sure the options bellow are enabled.

#define MOTOR1_USE_ULN2003_DRIVER
#define MOTOR1_PINOUT 12, 11, 10, 9

Pinout

28BYJ-48 with A4988 driver

This solution is not so much more expensive nor complicated but will give you much more torque from the exact same motor when compared with the Unipolar build. Use this configuration only with modded 28BYJ-48 stepper motors or with NEMA17 stepper motors. The example bellow shows a modded 28BYJ-48 but the connections for a NEMA17 are exactly the same.

BOM

Check the required BOM on the table bellow. The 100nF capacitor is only required if you intend to use Ardufocus in a Moonlite compatibility mode i.e. use Moonlite’s ASCOM drivers, if you intend to use Ardufocus ASCOM drivers then this capacitor is not required.

Settings

Edit your config.h file and set make sure the options bellow are enabled.

#define MOTOR1_USE_A4988_DRIVER
#define MOTOR1_PINOUT 12, 11, 10, 9, 8, 7

Pinout

PCB

BOM

Settings

Pinout