Electro-Mech Integration Meetings

Attendees: Mitchell.Ostler (Deactivated) Jonathan Xie

Objectives: UV cutoff merging with PD, power up sequence

UV Cutoff:

• Good to merge with PD

• maybe don’t merge with PS, cuz 1 MCU for all 3 might be too congested for firmware. TBD

• delete fuel gauge if battery/owen is ok w it

• fuel gauges

• conduct purely hardware validation on existing UV cutoff board soon (before new one is sent out)

• conduct firmware validation on existing UV cutoff (can read BATTERY_EN and send load switch enable signals). To be done after hardware validation

Power-Up Sequence

Critical Questions (in general):

• does UV cutoff power itself on start?

• does BPS need to be on before HV is turned on? Does it need to on before CC/PD are enabled? Or can it be on at the same time as LV system (CC/PD/etc)

• how is power selected when main switch is pressed (HV relay closed)

• what systems are powered by aux (on startup, and when do they ‘get off' aux)

• how does BPS cut off the battery (BMS relay?? what does it do and how, at each state)

• what do each of the driver controls (physical button vs digital button) do?

Next steps:

• Email ASC to clarify regs (when can BMS be powered by aux?)

• Reach out to past elec leads (Micah, Aashmika, Nita) to find out what they did

• Meet with Forest, Mitch, Owen, Battery Box, etc to discuss this (Wed July 12th)

Participants: Former user (Deleted) Mohamed Goha Jonathan Xie Yanshen Zhou Jasmine Thind Jenna Kong Owen Li Kostubh Agarwal Nicole Choe Shem Kim

Objective: sync discussion on: lights, power startup sequence, brakes, steering

Lights:

• Current enclosure is designed based on MSXVI

  

• LED board is in the YZ plane (if x the front-back axis of the car)

• Might have optics to focus the light more

• ENture surface is thermoformed over so light gaps can be as large as needed

• Todo get reference lights if we don’t already have

• How to get lighting requirements for side repeater? 5 degrees from body side

  • try not to have light stick out

  • What direction is reference light pointing? How is the reference light set up so we can replicate? Jasmine to email

• Taillight must be visible 10 degrees from perpendicular, so might have to drap around the side of the car

  • Requires 2 boards if we need that

• Confirmed will combine rear brake and turn

• To figure out mounting for center brake light and BPS strobe

• No combined turn/brake

  • One LED driver for both side DRLs

  • One driver per turn signal side

  • One driver for all 3 brake

  • One driver for BPS

  • Total 5

• Combined turn/brake

  • One LED driver for both side DRLs

  • One driver per turn signal side

  • one driver per brake light

  • one for BPS

  • Total 7

• Mostly todo: clarify reference

Whats the turn on process for the car?

• Person closes main control switch

  • Aux batt is connected to main relays (2 of them)

  • Aux batt directly connects to HV contactor switch, which you close

  • How do we power BMS from aux battery and then switch the power source?

  • What are we checking? Voltage and temperature and current?

  • When we close the contactors, what gets connected?

    • DCDC

  • Power BMS first to run self check

• How does BMS disconnect the pack if its connected to the

• Can we email the people to ask if BMS can be powered for a few seconds after

  • Also ask if power select/power distribution can be powered with BMS at the start

  • Also ask if it can power UV cutoff

• Talk to Mitch

• UV cutoff is active protection as defined by 8.3.A.5, which is no protection when there is no power. Do we need to add passive protection?

• Should we use primary cell for aux?

  • Probably not, since we can recharge aux batt any time so energy density is not that big of a concern

• Owen to get back to jonathan about cutoff voltage

• Aux battery will last at least one day, @Forest to see if thats is still true

  • 5Ah @ 12V, 60Wh, total driving time is 9 hours aux battery power consumption has to be less than 6W

  • Loads: 3.5W contactors, 1W for driver fan, Telemetry 2.5W, horn 0W which is 7W

  • To check regs if we can swap aux batteries whenever

• There is CAD for the battery box, Mo is working on main assembly

• Do we have thermal load for battery box

  • Allows us to reduce the LV power, BMS fans is the single largest LV load

  • Fans are part of the air duct that goes to the wheel

• To send battery box with battery if that wasnt sent already

• have searate battery box elec fw sync to talk about BMS architecture and general elec stuff in box

• mo working on assembled CAD model to come next week (to get git to work properly as well)

Solar Panel covering

• Nothing gets put on them

• The roof will have indents for where the panels will sit, everything will the flush

  • Some mech stuff mech people have figured it out

• Mo has solar panels in CAD

  • To get cutout locations

  • To make the specific 3d layout

How does regen braking work?

• one pedal driving?

• Jonathan to figure out how to deletect brake press and what it should connect to

• we need button to turn poff regen for brake testing

• No throttle is full braking

• Full pedal is full power

• to adjust gradient in testing

• Battery max charge current is 0.7c, 27A max charge current

  • 2700W

  • Set regen level to be lower based on batter percentage

  • Set cutoff for high SOC

  • regen will have to be limited

• Test regen efficiency on dyno when we get that working

• Jonathan to figure out how much braking is 2700W

• Wheel weels have not been designed

  • Don’t know how the openings will work

• Do we want a button to control fan speed? Probably

  • To check if there are extra circuits on steering stalk

• Forest to order some comically long USB cables

  • to see if long able off digikey

  • Cam to dash is 4-5m depends on how much we route it around

Participants: Former user (Deleted) Mohamed Goha Jonathan Xie Yanshen Zhou

Objective: lights, power startup sequence, brakes, steering

Auxiliary Battery:

• Currently planning on using 10S NiMH batteries (10 in series, electrically)

  • NiMH Cell: 1.0 V discharged, 1.2 V nominal, 1.45 V max

  • 46 x 22 x 22 mm per cell, so a 2x5 mechanical arrangement would be 110 x 92 x 22 mm, or 110 x 46 x 44 mm total size

• Alternatively, regs allow primary cells (non-rechargeable batteries) to be used, so could potentially look into that as an option

Lights (on canopy):

• Need to have 1 blinking red light to indicate a BPS emergency (by regs)

• Need 1 white light as a headlights

• Can maybe put the two next to each other, but have to discuss with Jasmine Thind

Telemetry (antennas)

• Antennas can’t be placed under solar panels (RF blocking)

• will most likely be included

Rear Camera

• Rear-view camera must be placed in the tail of the car, and can’t be in the top/roof enclosure

  • needs too large of a thermoform + distortion in order to fit on roof

• But, the camera in the tail can be routed to the telemetry Rasp Pi (in the rear enclosure). to process the data and send to dashboard via HDMI

Fans:

• By regulation, the driver’s face needs to receive airflow which is controlled by the car

  • so we NEED at least 1 fan for the driver

  • considering 2 fans, one on each side of the driver

Mounting Location Discussions

Battery Box Enclosure:

• The battery pack will need to be impounded and lifted directly up and out of the vehicle

  • Any boards located above the main pack in the battery box enclosure will need to have their cables disconnected from the car, and impounded along with the pack

Rear Enclosure

• There will be a relatively large space in the ‘driver’ section of the car (behind front enclosure, in front of battery box)

  • This depends on where the ballasts (weights to compensate for a light driver) are chosen to be placed

• Options for where this enclosure will be are:

  • 1) behind the driver’s seat

  • 2) under the driver’s legs

Tail Enclosure

• There is a very small (1in tall) but wide section along the ‘tail’ of the car, to house LEDs and rear camera

• LEDs will be mounted mechanically in series, in a thin strip along the width of the car

  • One LED on each side, so they can be turn signals (if powered individually), or brake lights (if both on together)

• Waterproofing:

  • LEDs: naturally waterproof?

  • Rear-camera: will require an O-ring, gasket, etc

Other Discussions

Power Budget

• Need to begin measuring the power consumption of all the boards to make sure we’re not consuming too much power!

  • DCDC is rated at 240W max! (20A at ~12V)

Connectors

• Need to figure out what type of connectors we will use throughout the car.

• Consider:

  • Max current & voltage

  • Type of mechanical connection (latching/non-latching, ease of disconnecting, etc)

  • Space constraints

Tentative Board Mounting Locations

Action Items

• Former user (Deleted) to sync-up hardware with strategy
• Former user (Deleted) to sync-up hardware with firmware
• Schedule regular hardware-mechanical integration meetings (Former user (Deleted) Mohamed Goha)
• Confirm mounting locations
• Follow up with members on dashboard design
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