Status: Inactive
Owner: None
Requirements
Passthrough 18 V - 55 V (6S lower voltage to 12S upper voltage )
Measure current through hall effect current sensing (without a shunt resistor to minimize losses)
Measures voltage with an ADC
I2C or UART interface
Preference toward I2C, but just pick one of them
XT90 connector for input power and output power
Maximum current passthrough requirements
Max pulsed current 200 A
Max continuous current 75 A
Refer to Nathan’s current power module, photos in discord, for a reference to what this board will be replacing.
Implementation Ideas
“High” voltage & current passthrough should be done with an XT60 connector.
Current measuring can be implemented with a smaller current transformer to be mounted on the PCB
A simple ADC integrated (presumably 2 channel ADC) and possibly voltage divider circuit can be used to measure both current and voltage
This ADC should support I2C and SPI and may be fitted with a signal buffer IC
Fairly standard to be able to find an ADC that can operate at 3.3V
A single “low voltage connector” should be used
This would be some relatively fine pitch connector
Some standard molex thing
Four conductors on this connector
GND (this will be signal ground, but should be presumed as the same potential and non-isolated from the “high voltage passthrough gnd”
5V or 12 V input power (possibly a range that supports each of these and maybe more)
I2C or UART data lines (2 conductors for each of these protocols.
Powering the ADC
The ADC and buffer (if a buffer is included, just an idea) will ideally consume very miniscule current, on the order of less than 200mA which makes a simple LDO (low dropout regulator) viable
This LDO will take the low voltage input power and use that to power the ADC chip.
LDO has lower efficiency than a buck, but will save board space and will be more convenient to implment.
Because of the negligible total power requirements for the board a low efficiency doesnt matter as much
High Level overview of Implementation:
Voltage fed through XT60 connector
Hall effect sensor measures the current passing through and outputs an analog voltage signal
Analog voltage signal is converted into digital signal.
Research:
Hall Effect Sensor
Operation: Outputs an analog signal upon detection of a magnetic field generated by flow of electrons (current). A greater current flow means a stronger magnetic field and higher flux density. Current flow through the hall effect VCC and ground pins. The introduction of an external magnetic field will influence the magnetic field of the moving current. The electrons deflected to one side which creates a charge imbalance which results in a potential difference across the sensor (Hall voltage). The level at which the electrons are deflected will allow for an analog output regarding the strength of the magnetic field. There are amplifiers within the sensor to amplify the input signals.
Output voltage is poproptional to product of current in the conductor and
Linear IC’s take continuous range input and outputs and outputs are mostly proportional to the inputs whereas digital IC’s output only low or high. Since I will need to take in and output a contiguous range of voltages, I will need a linear IC to get an output voltage that is directly proportional to the magnetic field that interacts with the sensor.
Hall Effect Sensor Considerations:
Linear: Output voltage can only be up to the saturation voltage that is determined by the power supply. Moving a magnet sideways across a hall effect sensor will give you an increasing analog signal as the pole becomes more and more in aligned with the sensor (doppler effect). An example of this setup is on opposite sides of motors to detect different operating characteristics (RPM, positioning, switches, proximity sensors )
Bipolar Vs Unipolar : Unipolar turns on in the presence of one pole and off when removed whereas in bipolar, it stays on until other pole is introduced.
Advantages of hall effect
No moving parts
Non contact
Low mainteance
Not affected by vibration, dust and water.
Example of current sense breakout board for ardunio:
https://www.sparkfun.com/datasheets/BreakoutBoards/0712.pdf
2. Current Sense Transformers:
Current sensing used for control, protection and information.
2. Analog to Digital Converters (ADC)
Measures ratio of analog input value to a reference value to express in the form of a digital value. The range is divided into n equally sized intervals and each interval is assigned to a certain value.
ADC with 8 unique values gives a resolution of 3 bit (2^N = 8 where N=3 ). Resolution defines the smallest change in input value that the converter can distinguish.
Offset and gain error can be compensated so that the end and start point of the curve are the same. However, there could be a non-linearity error
Since this project has stopped active development I’m just posting some random idea links
https://www.digikey.ca/en/products/detail/allegro-microsystems/ACS37612LLUATR-015B5/12093264