Automotive Robotic Controller PCB - Electrans

About This Project

During my work-term at Electrans Technologies, I was tasked with designing an interface for controlling their automotive robotic product. The electrical and mechanical design of this interface were solely my responsibility, and it was produced for client-use. The PCB layout and schematic were designed in just 2 weeks and I did the reflow assembly of 176 individual components in house.

Electrical

Overview

The right diagram depicts the PCB's capabilities: dual CAN bus communication, SD card logging, real-time clock management, and LCD display. It also interfaces with two digital inputs (E-STOP and control buttons) for user interaction. An arduino MCU is used to control the display for easy software implementation and communicates with the CAN enabled MCU over a custom 8 bit parallel bus.

Power Management

In this application, an ideal diode controller circuit offers several benefits for battery powered automotive use.

Voltage stability for the PCB
Reverse polarity protection
Low voltage drop (compared to shottky diode)

Reflow Assembly

For time constraint reasons and cost, the reflow assembly was done in house. To accomplish this the following was done:

Pick and placed 176 components
Soldered difficult pin package ICs and connectors (FPC connector)
Hand soldered connectors and wiring to the PCB

Schematic

The schematic for the PCB design is included to the right. Note that a hierarchal sheet management style was used to enhance readability.

DMIB_ALPHA_SCHEMATIC_rotated.pdf

Mechanical

Overview

Due to environmental and operational reasons the enclosure for the robotic controller had to conform to the following specifications

IP60 rating
UV resistant
Drop resistant from 2 meters height
Protection for screen
Aesthetically appealing
Employ mounts for an ESTOP, control button, LCD screen, an automotive connector, and a DB9 connector

Material Selection and Manufacturing

Due to minimal volume needs, 3D printing was chosen to optimize cost-effectiveness. Both SLS and SLA printing were considered, SLA was ruled out since UV-reactive thermosets become brittle over time due to UV exposure, this would make the enclosure susceptible to brittle fracture.

Material of Choice: Nylon 12

Method of Manufacturing: SLS Multi-Jet Fusion 3D printing

Electronics Packaging

The PCB and enclosure were designed in parallel:

PCB has notches to minimize size of the enclosure
The screen is mounted to the backside of the PCB to simplify assembly
The wiring for the buttons is soldered to the PCB and connected to the buttons with screw terminals

Final Product

Specifications

IP60 rated enclosure
Reliable PCB with very stable voltage regulation
Produced very reliable CAN messages using common mode choke filter
All peripherals operate as expected
PCB maintains less than 5°C temperature rise from ambient at peak operation intensity

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