Summary of "Embedded Systems and Design & Development - Feb 18, 2026 | Afternoon | VisionAstraa EV Academy"
Embedded Systems & Design — VisionAstraa EV Academy (Afternoon Session)
Overview — Core Topics Covered
This session focused on practical current sensing, signal conditioning, and temperature sensing for EV applications, with hands-on guidance and exercises using Arduino/Tinkercad.
Current Sensing
Sensor types reviewed
- Shunt (sense) resistors
- Hall-effect sensors
- Current transformers (AC only)
- Fluxgate and magneto-resistive sensors
Use-cases in EVs: motor current measurement, battery charge/discharge monitoring, and auxiliary systems.
Shunt / sense resistor design (tutorial + worked examples)
Purpose: convert current → voltage so an MCU ADC can measure it.
Example scenario
- Supply: 10 V source
- Load: 10 Ω–100 Ω → up to 1 A current
R_sense selection (theoretical)
- Choose R_sense by Ohm’s law to meet ADC full-scale. Example: to get 5 V at 1 A, R_sense = 5 Ω (theoretical).
Practical issues with large R_sense
- Power dissipation: P = I^2·R → 1 A^2 · 5 Ω = 5 W (heat, cost, inefficiency).
- Load loss can become unacceptable (in the example, about half the load power is wasted).
Practical approach
- Use a very low R_sense (e.g., 0.1 Ω → 0.1 V at 1 A) to limit power loss.
- Consequence: the voltage signal is small, so you need signal conditioning (amplification, instrumentation amplifiers, op-amps with negative feedback) and noise suppression to match ADC input range and resolution.
Grounding / placement
- Prefer ground-referenced (low-side) placement consistent with ADC reference when possible.
- High-side sensing requires differential measurement or amplifier stages and has different grounding implications.
- Ensure the sense resistor reference matches the ADC reference so measurements are accurate and safe.
Characterization & firmware mapping
- Plot/map Vout (ADC input) vs Iload. If linear, derive y = m·x (+ c) and invert to compute current in the MCU.
- Example ADC: ATmega328 10-bit ADC (0–1023 counts) with 0–5 V reference. Use the slope to convert ADC counts ↔ voltage ↔ current.
- Embed the conversion relation in MCU code for monitoring, protection (trip if I > threshold), and control logic.
Signal Conditioning & Implementation Notes
- Why amplify: trade-off between low R_sense (low dissipation) and ADC resolution — amplify small voltage signals to use the ADC full-scale.
- Typical sensor modules/ICs often include built-in amplification, filtering, and noise suppression.
- When designing custom hardware, include instrumentation amplifiers, proper filtering, and verify grounding and layout to minimize noise and offset errors.
Practical Exercise / Tutorial Guidance
Tinkercad exercise (block/text coding + Arduino) suggested:
- Build a circuit to monitor current via a sense resistor and ADC.
- Example demo: if measured current > 1 A, turn on the built-in LED (visual short-circuit protection).
- Debug tips:
- Test components individually (LED polarity/anode-cathode, current-limiting resistor).
- Use Tinkercad component help (hover terminals for labels).
- ADC data handling:
analogReadreturns integer ADC counts (0..1023 for 10-bit).- Convert counts → voltage → physical parameter using the mapped slope or lookup.
Temperature Sensing — Types, Selection, and Mapping
Sensor types reviewed and EV recommendations
Contact sensors
- Thermistors (NTC/PTC)
- Low cost and sensitive; NTC widely used in automotive.
- Nonlinear response; good for pack/motor/cabinet temperature sensing.
- RTDs (e.g., PT100)
- Higher accuracy and stability; used where accuracy matters.
- Wiring options: 2-, 3-, or 4-wire to compensate lead resistance.
- Semiconductor IC sensors
- Analog-output ICs (e.g., LM35): voltage proportional to temperature.
- Digital-output ICs: temperature over I2C/SPI — convenient and reduces analog wiring errors.
Non-contact sensors
- Infrared / thermopile sensors and thermal arrays (e.g., Panasonic AMG-style 8×8 thermopile arrays)
- Produce thermographs, useful for imaging; costlier and rarely required for typical EV thermal monitoring.
Out-of-scope for most EV apps (noted)
- Thermocouples (for very high temperatures)
- Fiber-optic sensors (specialty isolation/EMI environments)
Key design and selection considerations
Nonlinearity
- Thermistors are nonlinear. Two common ways to convert sensor output → temperature:
- Curve-fitting (mathematical model) — more computation, formula-based.
- Lookup table (recommended/practical) — sample sensor outputs vs temperature and store the map in MCU flash.
Accuracy concerns
- Lead resistance and wiring — use 3/4-wire RTD wiring or compensate via calibration.
- Sensor stability/drift and lifecycle — may require recalibration or algorithm updates.
Communication/architecture
- IC sensors often use I2C (SDA/SCL) or other serial buses — reduces wiring and simplifies integration. Throughput is adequate for slow-varying temperatures.
Safety / standards
- Select sensors and algorithms compatible with relevant automotive safety requirements (ISO levels, system safety integrity).
Implementation Pattern for Thermal Management
Example flow
- Thermistor on battery pack → ADC measures voltage.
- Map ADC/voltage → temperature via lookup table stored in program memory.
- MCU uses temperature for protection/control decisions (cooling, isolation, alarms).
Emphasize robust embedded code that accounts for ADC resolution, sensor nonlinearity, wiring errors, and defined safety thresholds.
Other Topics & Next Steps Mentioned
- Upcoming sessions: BMS control aspects (SOC/SOH computation), control/protection algorithms, HIL demos and other loop-simulation types (processor-in-the-loop, software-in-the-loop).
- Practical recommendations:
- Consult datasheets and application notes.
- Store lookup tables in MCU memory where appropriate.
- Test hardware in simulation (Tinkercad) before deployment.
Exercises / Hands-on Items (Summary)
- Tinkercad Arduino project: short-circuit protection demo using a current sense resistor; LED indicator when current > 1 A.
- Practice ADC scaling: convert ADC counts → voltage → physical quantity; understand 10-bit range (0–1023).
- Build sensor lookup table for a thermistor (sample outputs vs temperature), store in MCU flash, and map ADC readings → temperature in firmware.
- Debug tips: verify LED polarity, test components separately, use Tinkercad help text.
Tools, Components, and Examples Referenced
- Arduino / Arduino Uno (ATmega328) — 10-bit ADC example
- Tinkercad for prototyping/simulation
- LM35 (analog temperature IC)
- PT100 / RTD family
- Instrumentation amplifier / op amp (negative-feedback amplifiers)
- Panasonic AMG thermopile arrays (infrared thermal array example)
- I2C bus for digital temperature ICs
Main Speaker / Sources
- Instructor from VisionAstraa EV Academy (session presenter).
- References used in examples: Arduino Uno / ATmega328 ADC, LM35, PT100/RTD, Panasonic AMG thermopile family, and the Tinkercad prototyping environment.
Category
Technology
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