BPS Amperes PCB

Owner	@Nathan Lemma
Status	In progress
Contributors	@Nathan Lemma
Approver	@Lakshay Gupta
Due date	Nov 30, 2024
On this page	1 Design options 2 DECISION 1 3 Ideas 4 High Side vs Low Side 5 Follow up 6 Vocab 7 Resource files

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 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

	Option 1 - Voltage Across a Resistor	Option 2 - Magnetic Field of Wire
Overview	Current Sense Amplifier or Isolated Modulators/ADC	Hall-Effect Current Sensing
Screenshot
Pros and cons	Accuracy Simplicity and cost Affected by electric noise

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

	Current Sense Amplifier	Isolated Modulator
Design
Accuracy	Bigger shunt resistor allows for more accuracy
Power Dissipation	Smaller shunt resistor consumes less power

Follow up

#	Decision	Status	Next steps

#	Decision	Status	Next steps
1	Decision 1	Completed	Create the components for the prospective design
2

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