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❓ Problem statement
BPS is tasked with securing the safety and monitoring of the battery, such as current monitoring. Over-current of the battery can damage internal components and pose a risk to the driver.
💡 Research insights
There are 2 ways to measure current, either using a shunt resistor connected to the load or using a hall-effect sensor. They have their own pros and cons but they solve the same problem.
📊 Solution hypothesis
The solution is successful if we are able to track current reliably and transmit that data to the leaderboard.
🌈 Design 🪛 Design options
There are only 2 ways to measure current. Either measure the voltage across a resistor in series with the load or we can measure the magnetic field of the wire.
Option 1 - Voltage Across a Resistor | Option 2 - Magnetic Field of Wire | |||||||||||
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Overview | Current Sense Amplifier w/ Shunt Resistoror Isolated Modulators/ADC | Hall-Effect Current Sensing | ||||||||||
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Pros and cons
Preferred
Temperature Stable
Physically smaller
Affected by electric noise (can be isolated)
Power Effective
Low Drift
Affected by magnetic noise
Why use it when a resistor works anyways
Specs
Criteria:
Precision: 16bits
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DECISION 1
- Option 1 - Making the PCB though a shunt resistor
In the future, members can look into the second option for a hall-effect version
Ideas
Figure 1 is a common method to measure current using a shunt-resistor. There are 3 steps to read the current:
The differential voltage is fed into the Current Sense Amplifier and converted to a single-ended signal.
This single-ended signal is connected to an ADC, digitizing the signal.
The signal is sent to a microcontroller for processing.
High Side vs Low Side
For reading the current, there are 2 different configurations you can have your device hooked up to.
Figure 2 shows an example of the current sense amplifier connected to the shunt resistor in a high-side sending configuration.
Current Sense Amplifier | Isolated Modulator | |
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Design | ||
Accuracy | Bigger shunt resistor allows for more accuracy | |
Power Dissipation | Smaller shunt resistor consumes less power |
✅ Follow up
# | Decision | Status | Next steps | ||||||
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1Use Option | 1 for the base design of the boardDecision 1 |
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💎 Source files
Type /link to add links to design files.
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🔤 Vocab
Current Sense Amplifier: Amplifies the small voltage drop across a shunt resistor to measure current accurately in circuits.
Isolated Modulator: Converts analog signals to digital while maintaining electrical isolation, often used in high-voltage or noisy environments.
Hall-Effect Sensor: Detects magnetic fields to measure position, speed, or current without direct electrical contact.
Zero-drift: the phenomenon where a sensor's output signal shifts away from its baseline (or zero) value when there is no actual current flowing through the sensor; affects Hall-Effect Sensor
💎 Resource files
How to Sense Current |
Hall-Effect White Paper |
Shunt vs Hall-Effect |
Isolated Amplifiers vs Isolated Modulators |