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:

Information on the 'TimeIsMotion' software project which parses scripted serial commands to Meade DS DSM DS-2000 telescope heads (aka the 'milapse head') via the Autostar #497 handset.

WARNING! it has come to light that Meade has updated it's chipset on the #497 (now known as #497EG: http://tinyurl.com/y8nkz78) The new model will NOT work with this firmware.

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Engine Program Control

The time-lapse engine operates under the context of a 'program'.  The 'program' is considered to be the collection of your current settings, automating certain activities for you on a schedule.  The schedule is determined by the camera intervalometer, controlling how often to fire the camera and therefor when to move motors and check keyframes. You may change any settings during program execution, or even begin executing a program without having entered any settings.  (The result of this would be to have the program run timer incrementing for you.)

For example, a program may look like this:

Motor Control

The time-lapse engine supports control of up to four motors.  Each motor's settings are independant from the other motors, allowing distinct control of the behavior of each axis.

Note: motor movements are made incrementally to ensure proper performance.  That is, any movements needed by motor 0 will be made before motor 1, which will be made before motor 2.  This prevents timing issues during motor move execution that may cause jerkiness or un-reliability of a particular axis' movements.

The following controls are provided for each motor:

• Motor Enable
• Steps per Move
• Maximum Steps
• Linear Ramp Rate (output video speed control)
• Execute Down Ramp
• Direction
• Set Home
• Go Home
• Move Steps Now
• Backlash Compensation

 Camera Control

The time-lapse engine provides the following camera control functions:

• Exposure Time
• Interval (Cycle Delay)
• Post-Exposure Delay Time
• Pre-focus Tap Time
• Focus High with Shutter
• Maximum Shot Count
• Camera Repeat Cycle

Exposure and Interval timers are non-blocking, this means that you may continue to interact with the engine while a timer is engaged (e.g. during an exposure), or even trigger keyframes.  This is especially useful when you want to continue to modify your program based on time during the execution of your program.  Post-exposure and Pre-focus tap timers are blocking, however, and you may not expect time-based keyframes to execute during these actions.

Exposure Time

Introduction

The OpenMoco Time-Lapse Engine (OMTLE) is designed to run on an Arduino microcontroller with the Atmega328P Chipset.  It is provided as a C++ sketch to be uploaded via the Arduino IDE.  It can be easily ported to other microcontroller platforms as well.