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Description/Purpose

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

Physical

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• Discuss form factor and mounting with Cooling

  • Talked to Kaden Nguyen 10/12/24

    • Airflow sensor needs to be exposed - preferably back of board

    • Humidity/temp can be anywhere

    • Make as small as possible around PSOM

    • Mounting holes on corners

• Airflow only one direction - can have stuff on the other side of flow sensor

• Does not need to be waterproof

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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

  Modularity: Can pick and choose which sensors to use on each board during assembly – doesn’t require all sensors to be present

• 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

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• 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

CAN IC (WIP)

Need input on chip to use - or do we need it?

• Description:

• Justification:

• Datasheet link:

• Associated passives/components:

• Interface:

• Notes:

12v to 3.3v step-down (WIP)

Need input on converter - do we even need this on the board?

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Description:

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Justification:

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Datasheet link:

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Associated passives/components:

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Interface:

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TVS Diodes

PTC Fuses

Connectors (WIP)

• PSOM (53307-2471 connector)

• Power from CAN

• EnvironmentCAN

  • TODO

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