Engine Hardware

The OpenMoco Time-lapse engine is designed a minimal amount of hardware, using an easy circuit design that can be readily bread-boarded, or soldered to perf-board.

Schematic

The following schematic shows the basic layout of the circuit, with the arduino in the center, and the default pin connections to motors, camera, alt, etc.

Click on the thumbnail for a full-size image.

Parts List

To build the above circuit, you will need the following parts:

• (1x) Arduino Duemilenova or equivalent
• (2x) 4N28 Optocouplers [OK1-2] or (1x) NTE3086 Dual Optocoupler
• (6x) NTE5097A diodes [D1-6]
• (2x) 510-Ohm Resistors [R1-2]

Connecting Devices

The following connections must be made to the arduino:

M0_STEP, M1_STEP, M2_STEP

The arduino pins marked for connection to Mx_STEP connect to the "STEP" pin of your stepper motor's controller. 

Each connection should include a diode in-line, allowing the flow of current from the arduino to the stepper controller.  These diodes will prevent the stepper driver from feeding back electricity and damaging the arduino.  If your stepper drivers provide protection diodes, you may still wish to use your own to prevent the possibility of reverse voltage should you experience a short elsewhere.

Note: this circuit is only designed to work with stepper motor drivers that operate using a single input for step, and a single input for direction.

M0_DIR, M1_DIR, M2_DIR

The arduino pins marked for connection to Mx_DIR connect to the "DIRECTION" pin of your stepper motor's controller.

Each connection should include a diode in-line, allowing the flow of current from the arduino to the stepper controller.  These diodes will prevent the stepper driver from feeding back electricity and damaging the arduino.  If your stepper drivers provide protection diodes, you may still wish to use your own to prevent the possibility of reverse voltage should you experience a short elsewhere.

M0_GND, M1_GND, M2_GND

The arduino pins marked for connection to Mx_GND connect to the GROUND of your stepper motor's controller.  

You MUST connect the ground of your controller to the ground of the arduino, otherwise you will not be able to trigger them.

SUART_TX, SUART_RX

The arduino pins 2 and 3 are used to provide a software UART (serial) connection to another microcontroller or computer.  This connection is used when a secondary interface is connected.

If you connect the software UART to another device, you must connect its ground (SUART_GND) to the arduino's ground.

CAM_SHUTR, CAM_FOCS, CAM_COM

To control your camera, you must connect, at a minimum, the shutter control line and the common line (The tip and ring on a Pentax remote cable using a 2.5mm stereo plug) through the transistor side of optocoupler OK2. 

If you wish to control the auto-focus on your camera, you must connect the focus control line and the common line (sleeve and ring on Pentax remote cable) through the transistor side of the optocoupler OK1.

A 510-ohm resistor should be placed between the arduino pin and the anode of the optocoupler.