PCM Box
Compact Design
Three main boards, the Powertrain Control Module (PCM), Standalone Data Logger (SDL), and Power Distribution Unit (PDU), are packaged as efficiently as possible, sliding on rails and connecting to the PCM connector board with gold fingers. The design incorporates poka-yoke style keyed slots such that boards can’t be inserted upside down or in the wrong slot. The middle divider also doubles as a support for the widest board, the PDU, in order to reduce board flex and vibrations while driving due to the 8 heavy 18650 batteries. The enclosure is 3D printed in ASA plastic to remain as light weight as possible, and uses heat set threaded inserts for secure attachment of components.
Optimized for Accessibility
The PCM box features a latched access panel on the outward facing side for easy access to the boards with fast attachment and detachment, necessary during frequent debugging while testing the car. The inward facing panel secures the connector board, where 5 autosport connectors link the PCBs to the car’s wiring harness. The 3D printed parts are coated with a sealant for waterproofing, and each panel is designed with an overhung edge and gasket foam to seal the interface. The front panel can either be sealed by the sprung latches, applying a clamping force, or with 6 screws for a more secure seal for added protection during competition events.
The box is attached to the chassis with two tabs and positioned in an easily accessible spot for both the outward panel, which is used to access the boards, as well as the inward panel where the wiring harness connectors must be attached, all while fitting between the suspension and seat firewall.
Project Summary
The PCM Box was one of my first personal projects Sophomore year working with Auxiliary Systems / Enclosures on Penn Electric Racing
I was tasked with designing an enclosure to house new electrical PCB’s as part of the Powertrain Control Module. The design criteria were to create a light-weight structurally sound and waterproof box to hold the PCB’s while being easily serviceable.
I designed the enclosure inspired by the previous version which was an extruded aluminum box about half the width. I decided to use 3D printing to reduce weight while accommodating the larger boards and added latches to be able to easily open and close the lid, along with foam gaskets for waterproofing. I also designed flanged chassis tabs and strategically located the box where it could be accessed by hand without removing any other components.
After testing a few iterations and tweaking dimensions, a process made easier by the rapid prototyping ability of 3D printing, the final product went on the car and served its purpose as designed over several testing sessions and at competition. The accessibility features proved invaluable in saving time while electrical changes were made to the boards throughout the testing process.