Maddie’s research and notes on the accel and brake pedal sensors we’ll be using.

Preliminary Notes

Purpose of sensors

In the 2024-2026 car, Controls will need to detect the position of the accel pedal for movement, as well as the position of the brake pedal for fault conditions and telemetry. While the position of the acceleration pedal is necessary, the position of the brake is technically optional- all Controls needs is to enable the brake lights. However, for the purpose of analysis and additional features, we want to measure the position of the brake pedal and the pressure in the brake fluid line to

• Send measurements to Data Aq for analysis

• Detect and display a fault when there are discrepancies between the brake pedal position and brake fluid line

• [ Possibly adjust the brake light brightness ]

and these sensors will be under Controls since we require it for the car state and therefore would like to receive this data as fast as possible (in short, we need it more/sooner than Data Aq).

What did we do in Daybreak?

In the 2024-2026 cycle, we used a linear potentiometer for the accelerator pedal, and a button for the brake pedal (since entering brake state is a binary decision).

Linear potentiometer

• 50mm Stroke (measuring length)

• Cost: $144

• SKU: SLPC 50 A 2K 1M (621400)

• Compact linear displacement transducer with rod end bearings

• 2KΩ resistor value

• 18mm diameter (housing)

• IP65 Rating

• Connector: plug type w/mating connector included / Cable: 1 m length (3 wire)

• Intended for industrial applications

Notes:

IP (Ingress Protection) Environmental Rating: Standard for the resistance of the part to environmental conditions like dust and moisture.

How to read the rating:

IP[Protection from solid objects][Protection from liquids]

Protection from solid objects: 0 (none) - 6 (no ingress)

Protection from liquids: 0 (none) - 9 (high-pressure hot water from different angles)

Why did we choose this sensor?

“linear was a relatively arbitrary choice made by me bc it was the first one I found with a good mechanical rating” - Sid

Sensor Research

Key Parameters

• Mechanical Rating

• Accuracy

• Type (angular potentiometers, brake line pressure sensor)

• Output (ideally supports digital protocol we use)

• Cost (to some extent)

• Size

References

https://www.reddit.com/r/FSAE/comments/ab3gs3/brake_pressure_sensors/

• https://www.summitracing.com/parts/sum-890004

• Industrial wet pressure transducer from Mouser or Allied

• Honeywell MLH200

• pressure switch rated for hydraulics

• https://www.aim-sportline.com/en/products/sensors/index.htm#pressuresensors

• For brake pedal (not line): load cell to measure force

https://www.fsae.com/forums/showthread.php?751-Brake-line-pressure-sensor&s=24ff250b660f943588ee776b1167bec7

• Digikey MSI, 0-1000ish psi

• https://www.digikey.com/en/products/detail/honeywell-sensing-and-productivity-solutions/MLH02KPSB06A/1248869?s=N4IgTCBcDaICwA4AMBaMBWAzHFA5AIiALoC%2BQA

https://www.fsae.com/forums/showthread.php?12194-EV-Car-brake-pressure-sensor

• Linear potentiometer may be cheaper?

• Can call to see if company will give a discount

• Radio volume potentiometers have been used with suspension measurements- cheaper but less precise

• Ebay

https://fsaeparts.com/collections/for-the-car

• https://fsaeparts.com/collections/for-the-car/products/linear-position-sensor?variant=564772409

https://www.hpacademy.com/forum/general-tuning-discussion/show/brake-pressure-sensors/

• 2000psi honeywell

https://www.apexspeed.com/forums/showthread.php?53094-Brake-Pressure-Sensor-Installation

• On installation

• “Banjo” bolts

https://www.reddit.com/r/FSAE/comments/5vvg3v/accelerator_pedal_position_sensor_apps/

• Rotation angle using hall sensors

• linear displacement

https://electronics.stackexchange.com/questions/173609/measuring-angle-position-of-a-pedal

• Rotary potentiometer

• https://en.wikipedia.org/wiki/Rotary_variable_differential_transformer

• TI inductance-to-digital converters

https://www.fsae.com/forums/showthread.php?877-Pedal-and-sensor-assembly

• https://www.parker.com/content/dam/Parker-com/Literature/Electronic-Controls-Division/Literature-files/RS70_datasheet.pdf

Aiden’s Notes

• Rotary Potentiometers

  • Easier to integrate (slides directly onto the pedal)

  • Make sure to get one with a measuring angle of similar size to the pedal rotation

  • Will require a bit more work on our end to convert “degrees” into a useful number for us to use

  • Waiting for Ergo to make decisions to proceed

• Break Line Pressure Sensor

  • Most pressure sensors are pretty similar as far as I can tell besides threading and the amount of pressure they can handle

  • We are using 3/8-24” threading and 50-600psi

  • A potential option that other teams use

    • https://hhrperformance.com/i-31646738-aim-brake-pressure-sensor-dash-3-3-8-24-0-100-bar.html

    • I’m not confident that this will hold up over time

  • This is a more industrial option

    • https://www.mouser.com/ProductDetail/Kavlico/P265-1000G-F2A?qs=bZC7aUKSI5%2Fp83lG5BHXWw%3D%3D

    • With materials dedicated to standing up to brake fluid at high pressures over a long period of time

    • It also has better accuracy

    • $150