G-EDM Gapstorm (Pulseboard)

The G-EDM Gapstorm was designed to replace the EVOIII Pulseboard with a more user-friendly, compact, and efficient version. It simplifies the build process, reduces size, and enhances performance.

Overview: The Gapstorm is the new standard switching unit in the G-EDM topology, built around a DPH8909 or DPM8605 step-down converter. It enables makers to cut various metals with high precision on DIY wire or RAM EDM machines. Note: DPH8909 (or DPM8605) are available with different interfaces. The TTL version is required and the baud rate needs to be set to 115.2k in the menu in order for the communications with the firmware to work. Read the manual on how to set the baudrate on those devices.

For more details, visit: https://gedm.org

To build a G-EDM it also requires the motionboard that can be found here: https://www.pcbway.com/project/shareproject/W532897ASC41_motionboard_evoIII_rev3_bb113e0f.html

Key Improvements compared to the EVOIII Board:

•   Compact Size:

    PCB footprint reduced to only 99mm x 99mm.

•   Simplified Manufacturing:

    Some through-hole (THT) components replaced with surface-mount (SMD) versions for easier assembly.

  Integrated Current Shunt:

•   The current shunt resistor is now onboard, reducing wiring complexity.

•   Upgraded Op-Amps:

    Replaced LM358 with OPA350 for improved performance.



•   Advanced Gap Proximity Sensing:

    Features two sensing channels: one for current feedback and one for voltage.

    Unlike EVOIII, which connected voltage sensing to the power bus and detected only hard shorts via voltage drops, Gapstorm’s voltage sensing provides fast, linear, real gap proximity detection.

    Requires firmware update to utilize this feature.

    The PCB includes a footprint for converting between gap proximity sensing and bus voltage sensing by unsoldering and repositioning a resistor.

Wiring and Calibration Enhancements:

•   The onboard shunt resistor simplifies wiring, eliminating the need for an external shunt wire.
•   Uses a fixed voltage divider for voltage feedback, removing the need for calibration potentiometers and making setup plug-and-play.

Power Mosfet Improvements:

•   Replaces four parallel IRFP260N Mosfets with a single, screw-mounted SOT-227 package.
•   The new Mosfet's package is electrically isolated from the drain, allowing direct mounting onto the metal enclosure, which acts as a large heatsink.
•   No soldering needed; just screw the Mosfet onto the enclosure with a touch of cooling paste recommended.
•   This design simplifies assembly and enhances thermal management.

Mechanical Recommendations:

•   Use 2mm thick PCBs to prevent flexing when opening the large Heavy duty WAGO terminal levers.
•   The PCB features four mounting holes for custom installations but is primarily mounted by screwing the Mosfet into the enclosure and securing the board onto the Mosfet.

Firmware:

  The latest firmware is available on GitHub (note: repository will be published within a few days):

https://github.com/G-EDM?tab=repositories

The upcoming firmware unlocks the new sensing features, optimizes performance and improves the surface finish.

Users that already have an EVOIII board can upgrade it without much issues to match the Gapstorm performance and also have the new voltage sensing. It is easy to do and a tutorial will be provided together with the firmware.

Image showing how to wire everything is available here:

https://gedm.org/photos/1/album/a655d21b876f5ba21783beb6c846ac8f

Layers (from top to bottom):

Top: pb-gapstorm-F_Cu.gbr

Second: pb-gapstorm-In1_Cu.gbr

Third: pb-gapstorm-In2_Cu.gbr

Bottom: pb-gapstorm-B_Cu.gbr