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:
  • analogRead returns 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:
  1. Curve-fitting (mathematical model) — more computation, formula-based.
  2. 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

1. Thermistor on battery pack → ADC measures voltage.
2. Map ADC/voltage → temperature via lookup table stored in program memory.
3. 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)

1. Tinkercad Arduino project: short-circuit protection demo using a current sense resistor; LED indicator when current > 1 A.
2. Practice ADC scaling: convert ADC counts → voltage → physical quantity; understand 10-bit range (0–1023).
3. Build sensor lookup table for a thermistor (sample outputs vs temperature), store in MCU flash, and map ADC readings → temperature in firmware.
4. 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.