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

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• 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

Open

Humidity Sensor

Open

Airflow Sensor

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…