Cases for Sinara@DIOT modules

[kaolpr]

Sinara@DIOT modules are currently exposed printed circuit boards (PCBs). When users remove them from a crate, the modules are vulnerable to electrostatic discharge (ESD) and physical damage from handling. This also exposes fragile components to accidental contact.

We propose developing a simple, cost-effective, and standardized protective casing for all Sinara@DIOT modules. The design should be inspired by existing solutions, such as the casings on NI PXI modules (see here), which use a combination of plates, spacers and sheet metal.

Design Requirements:

• Protection: The casing must effectively shield the PCB from direct contact and ESD.
• Standardization: One universal design should fit all standard Sinara@DIOT modules to simplify manufacturing and inventory (we however assume different case for Kasli DIOT and EEM FMC Carrier due to their specifics).
• Cost-Effective: The design must be economical to produce and easy to assemble.
• Compatibility: At this point of DIOT implementation (i.e. most of the modules are at the prototype stage) we can do adjustments in the designs to accommodate mounting holes for the casing.

Scope and Exceptions:

• In Scope: All standard Sinara@DIOT modules
• Exception: Kasli DIOT will require a modified design due to the height of its SFP cages. However, the concept and materials should remain consistent with the standard casing. Also EEM FMC Carrier will require modified design to enable FMC assembly.

The proposed design consists of:

• Top Cover: A flat metal plate mounted on spacers.
• Bottom Cover: A single piece of bent sheet metal screwed to the top cover spacers.

This approach seems to provide a good protection while keeping manufacturing simple and costs low.

Initial Prototype

As a proof of concept, @gravelpitman has created a prototype design for the AUX PSU module.

3D model: https://autode.sk/45x8nKr

Any comments on the idea would be appreciated.

[gravelpitman]

This concept would be easy to customize for odd modules such as Kasli.
I created a quick visualization of a Kasli enclosure that incorporates a structural brace to reinforce the front panel.
Please refer to the link below.

*Note that the visualization includes heavily modified versions of Kasli and Kasli SBC, which I will describe in a separate issue.

https://autode.sk/4l9WDTQ

[gkasprow]

LGTM

[marmeladapk]

Will this restrict airflow for components on the bottom side?

Is there a risk of cuts on users' hands?

[gkasprow]

It needs testing

[gravelpitman]

@marmeladapk It may slightly restrict airflow. Vents can be added to the side of the bottom cover to improve ventilation.

"(Is there a risk of cuts on users' hands?"
That depends on the manufacturing specifications etc. If the enclosure is powder-coated, the risk of users cutting their hands is minimal."

[gravelpitman]

The guidelines have been updated. (#97 (comment))
I've prepared guidelines for adding the necessary features to PCBs to enable enclosure assembly.

[gkasprow]

pls update the DIOT template and add the keepout zones on the top and bottom side

[gravelpitman]

While working with @martafafara on Kasli DIOT with enclosure, we noticed that the bottom cover’s bent flanges caused clearance issues under the PCB. Since Kasli requires that space, I removed the flanges, which also improves airflow. I also fixed the bottom keepout, previously I hadn’t accounted for the bent part of the screw island. The guidelines above have been updated accordingly.

At the link below you can find a visualization of the Kasli DIOT panel and enclosure. The Kasli DIOT revision is still in progress, so it may contain element collisions, etc. https://autode.sk/4nRQEop

[gravelpitman]

We worked with @martafafara on several modules (Kasli DIOT, FastServo, and FMC Carrier).

My initial enclosure concept proved to be suboptimal. The first row of mounting holes was positioned too close to the front panel (FP) mounting holes, which interfered with the ESD components that must be placed near the FP mounting points. In modules such as the FMC Carrier, too many mounting holes were concentrated near the top bracket, resulting in reduced PCB mechanical strength.

I developed a revised concept that eliminates the first row of mounting holes. From a PCB design perspective, this introduces only a single change; therefore, even if a new PCB revision has already been created based on the enclosure-related guidelines, it should not pose a problem. Additionally, I introduced bent flanges to connect the enclosure to the front panel. This modification requires two additional holes in the front panel. The enclosure was designed so that its front flanges do not restrict the front panel opening any more than the front panel brackets.

A 3D model mockup is available at the link below.
https://autode.sk/4q1m4Kz

Updated guidelines

Keepout areas are marked as hatched