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Status: InactiveActive

Owner: NoneZen & Chris

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

• Steps down input voltage to clean 5V and 12V rails

• Refer to Nathan’s current power module, photos in discord, for a reference to what this board will be replacing.

Current Sensing

Based on the above analysis, using an INA228 IC seems to be a better option for simpler implementation and integration. To minimize the losses with the shunt resistor, a resistance of 0.0005 ohms will be used (the current power module also uses this value). At max current of 75A, the resistor will dissipate 2.8W. To prevent overheating, a nonstandard resistor with a resistance of 0.0005 ohms and a power rating of 8W will be used, such as the one below.

https://www.digikey.ca/en/products/detail/koa-speer-electronics-inc/PSL2NTEBL500F/1039674

Implementation Ideas

• “High” voltage & current passthrough should be done with an XT90 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.

• Alternatively, use the 12V and 5V stepped down from the input line to power all board ICs instead of plugging in external power

• 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

...

1. Voltage fed through XT90 connector

2. Hall effect sensor measures the current passing through and outputs an analog voltage signal

3. Analog voltage signal is converted into digital signal.

4. Digital signal fed into MCU or application specific IC to be transmitted onto an I2C/SPI/UART bus

5. Input voltage broken down into 12V and 5V filtered clean rails

Previous Research:

1. Hall Effect Sensor

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