Byron Hopps / circuit design, mechanical/electrical integration

If you organize a 1-on-1 with this person, then fill in the timeslot and your name in the table below.

Feb 22

General - 2nd gen member of ISC (and CalSol), now working on Apple

Question 1: What are your thoughts on E-Fuses (BTS7080-1EPA or TPS1H160-Q1) vs traditional fuses for LV circuit protection?

• They both work - e-fuses are better to plan since they don’t blow. Are a little less failsafe - little more potential to go wrong - bigger fuse in case

• maybe have a 1A fuse and a 10A fuse just in case in series

•  

Question 2: What's the best lab equipment investment that you would recommend / the places you've worked have bought?

• A good power supply - to actually charge the pack with

• Source Measure unit (good battery simulator)

• Saelea Logic Analyzer - student pricing - has analog channels as well

• Boards for the car - assembled by people they trust - 3 boards. 1 to use, 1 to lose, 1 as a spare

  • Sometimes reflow the bottom, hand-solder the top

  • Tweezer line, everyone has a few parts

  • Have a soldering party

• Board preheater - meccal, buy the cheap one if it breaks then get something better

• JBC, Thermaltronics, meccal, etc. can dump heat really fast

• Knowing assembly process means we can select parts that work for this.

Question 3: What are the general approaches you take for deciding when to modularize systems?

• Splitting it up more in order to make sense

• Ask why you’re doing things the way you’re doing

• Spread out boards and have boards that do one thing well

  • Makes it easier for firmware as well

  • there can be too much modularity

  • Subboard for each lights driver might be too much…

  • More generic boards can be used on multiple cars.

• Think of where custom electronics for a competitive edge

Question 4: To follow up with a discussion you had during your presentation, what suggestions might you have for counteracting car vibration when designing board mounts?

• The mechanical bits

  • Connectors, buttons, switches, relays - these will give you problems

    • electromechanical components will give you problems

  • Lok at vibration specs

  • make sure that every fastener is secure with support mechanism - even for electrical systems

  • Strain relief - gluing part to board

  • Can stuff vibrate out?

  • Are the wires close to edges - you can cut through the insulation

  • Likes to avoid wires - keep it nice and simple

  • improperly crimped connectors where there is a stranded wire that foes and vibrates and fails strand by strand

    • avoid screw terminals

  • must have faith in isolated connections (not easy to remove on the fly)

  • Strain relief

    • How the wire joins the pin - solder will wick up through the strands

    • Spread out the strain

    • Small wires (higher gauge) are what matters the most - more strand have to fail before you have a problem

Question 5: What kind of efficiencies for the main low voltage systems DCDC converters have you seen from other teams, and what are the heat dissipation methods you have found are used most often with them?

• Vicor that they used didn’t require active cooling (nor a heatsink) -

• If you have to heatsink a VR - you should think about making this more efficient. If you get rid of X watts, then make the converter more efficient

• Moving serious power - definitely target above 95%

• MPPTs - they have their own - 50g and same efficiency as the Elmar Solar ones.

  • Derek Chou - IEEE explore will have a paper on it

  • GAN Fets. The best stuff is made by solar car teams.

Feb 21

Question 1: What are the most common causes for electrical failure during competition?

• People plugging the wrong connectors

  • fix with plugs that can’t be plugged in the wrong way

  • reverse voltage protection

    • PFET

      • zener diode for higher input voltage range

    • fuse for overcurrent

    • zener clamp

• Spraying water on the solar array (for keeping cool)

  • need appropriate drainage

• Not securing wires/cables

  • crimped connectors recommended

Question 2: Numerous teams have implemented sequential lighting. Do you have any advice for designing these?

• Specific board for sequencing

  • keep in mind things like turn signal vs hazards

• Need to be able to split LED arrays into segments.

Question 3: What would be the limiting factors in terms of electrical integration if making a solar powered EV larger than a cruiser (e.g: van for instance) ?

• Sun needs to be powering a significant portion of car during operation. Not possible with current technology.

• Solar panels need to improve (the hard part)

• Electric motors also need to improve (realistic)

Question 4: Apart from battery technology, what other key areas in the system do you think need the most innovation to make EVs more accessible to the consumer market?

• See above

• Electric power train; efficiency so high in electronics that active cooling is no longer required.

Question 5: What would you say would be the best ways to learn circuit design for people who are new to it, especially in a remote environment ?

• By doing - kinda hard in COVID though lol

• Doing layout/schematics

• “I wonder how xyz works” + simulations (ex. using LTSpice)

• Discrete logic/FPGAs instead of software control

• Talk to people and ask the right questions (leads/alumni e.t.c)

Question 6:

Insert answer here…