Prototype eval

OpenSync

An open source synchronizer for the velocimetry of fluids using a Raspberry Pi microcontroller.

Notice

The first batches of PCBs were ordered from JLCPCB for testing. If and when the PCBs pass testing and an initial PIV experiment is performed, the 1.0 milestone and initial release will be made along with a journal submission to HardwareX or JOH for publishment. Additionally, complete replication instructions will be included during the 1.0 milestone.

Purpose

OpenSync is a simple and low-cost synchronizer based on microcontroller technology. Due to the intrinsic nature of microcontrollers compared to more advanced devices (e.g., field programmable gate arrays), sub-cycle accuracy and complex features that are typical of commercial propietary devices are not implemented. However, OpenSync remains sufficiently flexible and provides enough support for most users' needs when performing a PIV experiment. This is because OpenSync is a digital delay/pulse generator capable of having each output channel individually programmed. In adition to an all-microcontroller platform and a custom PCB, OpenSync devices provides a low-cost means to deterministic control of laboratory equipment.

Basic Specs

• System Frequency: 250 MHz (4 ns resolution)
• Output Channels: 8
• Input Channels: 2
• I/O Channel Voltage: 3.3V or 5V @ high impedance

For a more detailed specification, please read the datasheet.

Documentation

The complete documentation for OpenSync can be seen here. Instructions to construct and use OpenSync are referenced here. User's interested in the development process of OpenSync are kindly refered to the SDLC documentation. There is a lot of information on the development process including some quirks from the pico microcontroller platform. Issues during construction or operation can be raised via GitHub issues to spread awareness.

Acknowledgments

OpenSync thanks Dr. Ivan Nepomnyashchikh and Professor Alex Liberzon for spearheading open source, open hardware equipment for the OpenPIV project. The original OpenPIV discussion helped initiate this project. Cost effective commercial PIV systems from Optolution provided a strong inspiration to complete this project. Additionally, certain hardware from MicroVec Pte Ltd was used as inspiration in earlier prototypes.

Responsible AI

The use of large language models (or LLMs) within this project is disclosed under the Responsible AI Disclosure.

TODO

• Add timing plot utilities
• Add device containerization for customization
• Add the ability to change channel names
• Add the ability to disable output channels (necessary?)
• Add three internal timers that can be mapped to pulse sequences
• Add the ability to count and skip external triggers (usefull for phase-locked stuff like rotor blades)
• Add second external trigger and output port masking
• Update firmware and software to reflect new design
• Get the damn production PCB produced
• Lower cost of PCB further (currently up to ~$100 USD per board)
• Validate new PCB against an osciliscope (mostly power planes; outputs seem okay)
• Add video examples on YouTube

References

1. Radim Hošák, & Miroslav Ježek. (2018). Arbitrary digital pulse sequence generator with delay-loop timing. Review of Scientific Instruments, 89(4). https://doi.org/10.1063/1.5019685
2. Scallon, A. (2017, June 18). Arduino TTL Pulse Generator and Controller. Optogenetics and Neural Engineering Core. https://optogeneticsandneuralengineeringcore.gitlab.io/ONECoreSite/projects/Arduino%20TTL%20Pulse%20Generator%20and%20Controller/
3. Starkey, P. T., Turnbaugh, C., Miller, P., LeBlanc, K.-J., & Meyer, D. H. (2024). Experimental timing and control using microcontrollers. Review of Scientific Instruments, 95(10). https://doi.org/10.1063/5.0225550
4. Stasicki, B. and Ehrenfried, K. and Dieterle, L. and Ludwikowski, K. and Raffel, M. (2001) Advanced syncronization techniques for complex flow field investigations by means of PIV . 4th Intern. Symposium on Particle Image Velocimetry, Göttingen, Germany, September 17-19, 2001.

Licensing

• Software: All firmware and software components are covered by the GNU GPLv3 license.
• Hardware: All hardware is covered by the CERN-OHL-S-v2 license.