Project Ownership: Ravi Shah

Github Link (Main Board): https://github.com/lhr-solar/DataAcq-EnvironmentBoard

Github Link (Breakout): https://github.com/lhr-solar/DataAcq-EnvBreakoutPCB

BOM Link: WIP

Description/Purpose

Measure environmental data throughout the car, including humidity, airflow, and temperature (see data acquisition SRR for more rationale)

Physical Design

• Each node consists of main environment board + sensor breakout board

• Main environment board - interfaces with PSOM to provide ADC, I2C, and CAN functionality; connects to breakout board via short (TODO: wire size/constraints) wire

• Sensor breakout board - implements exposed humidity, airflow, and temperature sensors with all passive components and connectors to the main environment board

• Modularity - can pick and choose which sensors to use on each breakout board during assembly

  • Doesn’t require all sensors to be present

Rationale

• Sensor board needs to be as small as possible to not disrupt airflow in the intake, exhaust, battery box, etc. (according to Cooling/Emech)

• Main board has to be at least the size of PSOM + any connector footprints, which is too large to place in the cooling system

  • Decided to break out sensors onto a separate board to balance airflow and data integrity

• Airflow sensor needs an uninterrupted flow of air to measure accurately - no other components can be placed in the line of measurement

• Humidity/Temperature sensors must also be exposed to the environment that’s being monitored

Interface

• Main environment board

• will send all environment data to the main Environment Leaderboard via internal Data Acq. EnvironmentCAN

  • Will then be sent over TelemetryCAN to the telemetry module

• TODO: breakout system

  • TVS for i2c, fuse, connectors

  • pinouts for connectors on board silkscreen if also using for logic analzer debug points

  • possibly need i2c repeater: https://www.nxp.com/products/interfaces/ic-spi-i3c-interface-devices/ic-bus-repeaters-hubs-extenders/level-translating-ic-bus-smbus-repeater:PCA9509

Context

Location of the board: Several boards will be located throughout the car as outlined below

• Cooling

  • Nose Intake, Tail Exhaust, Battery box intake/exhaust, internally in battery box multiple locations

• any other systems needing environmental sensing TBD

Connection List

Daughterboard Connection List

Main

Sensor Schematics

Protection for Breakout Board

Main Board Connector

Breakout Connector

List of Circuit Components

Humidity Sensor – https://sensirion.com/products/catalog/SHT45

• Description: Digital relative humidity and temperature sensor

• Justification for selection of specific part: ??

• Datasheet link: https://sensirion.com/media/documents/33FD6951/662A593A/HT_DS_Datasheet_SHT4x.pdf

• Associated passives/components:

  • 100nF capacitor

  • 2x 10k resistors

• Interface: I2C

• Footprint: weird footprint

  • Breakout: https://www.adafruit.com/product/5665

• Should work for driver development/testing

• Notes:

  • 3.3v supply voltage

  • Maximal power-up time = 1ms

  • Also measures temperature – not using this functionality due to modular nature of board

  • Accurate to ±1.0 %RH

Airflow Sensor – FS3000

• Description: Air velocity sensor module with 12-bit digital output

• Justification for selection of specific part: ??

• Datasheet link: https://www.mouser.com/datasheet/2/698/REN_FS3000_DST_20230207-3075780.pdf

• Associated passives/components:

  • 3x 0.1uF capacitors

  • 1uF capacitor

• Interface: I2C

• Footprint: also a weird one

  • Breakout: https://www.sparkfun.com/products/18768

    • Possible choice but expensive so maybe find an alternative?

• Notes:

  • 3.3v supply voltage

Temperature Sensor – https://www.ti.com/product/LMT87

Description: Analog temperature sensor with Class-AB output

• Justification for selection of specific part: ??

• Datasheet link: https://www.ti.com/lit/ds/symlink/lmt87.pdf?ts=1728144032765&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLMT87

• Associated passives/components:

  • 0.01uF capacitor connected between Pin 4 (VDD) and GND, other VDD pins connect to power plane

• Interface:

  • Analog - output voltage inversely proportional to temperature as shown below

    

• Footprint: SOT(5)

  • Breakout Board

• Notes:

  • 2.7v to 5.5v supply voltage

  • 0.7ms power-on time

TVS Diodes - https://www.onsemi.com/pub/Collateral/ESD9B-D.PDF

Description:

PTC Fuses - https://www.mouser.com/ProductDetail/530-0ZCM0010FF2G

Description:

Connectors (WIP)

• PSOM (53307-2471 connector)

• Power from CAN

• EnvironmentCAN

  • TODO

Layout (WIP)

Dimensions: 59x53mm (Main), 27.2x19.4mm (Breakout)

Requirements/Constraints: As described in rationale above.

Design Choices (WIP)

PCB

3D Models

Additional Considerations…