Old design: https://github.com/lhr-solar/Blackbody
Blackbody A - central board to read temperature and light intensity data for MPPT algorithm input and telemetry data
Blackbody B - for testing irradiance per cell, module, and array
Blackbody C - holds the irradiance sensors (and potentially the temperature sensors)
New plans
We realized that stretching I2C wires over long distances is problematic due to noise and increased capacitance, which would decrease the stability of our information. Adding an I2C extender should improve stability.
The irradiance sensors have unchangeable addresses, resulting in address conflicts. Adding a mux will allow us to have multiple I2C connections.
Why have we used RTDs specifically for temperature measurements? Thermistors and thermocouples are more commonly used for solar panel temperature measurement.
D2 said they can embed thermocouples into the solar modules. These would give us more precise data about the solar module temperature.
We can also use our own temperature sensors to measure the ambient temperature (temperature of the air around the solar panel). Thermistors are cheaper and more accurate than RTDs, and while RTDs go up to higher temps, for our application thermistors should cover our range.
Adding a mux to decrease the number of pins needed to read temperature data (and decrease number for R2Ds needed)
Considering the possibility of putting the temperature sensors and irradiance sensors on the same board (blackbody c). This could reduce wiring needs, especially if we also end up using the back-of-module sensors.
Decisions
- Layout + numbers of blackbodies and related sensors → breakout boards for sensing? multiple blackbodies? internal can communication?
- Thermistor to use for temperature sensing
- I2C extender to use
- I2C mux to use
- Thermistor reader to use
- How to secure the blackbodies/sensors
Blackbody A
Hardware Requirements:
Purpose: to collect light-intensity and temperature data of the solar array
Components:
sensing_temp:
Thermistor:
Thermistor-to-digital converter:
MUX
sensing_irr:
Irradiance sensor: TSL2591, can run at slower speed to limit noise and can collect irradiance data at slower intervals to limit computational power used
I2C communication/noise regulation
controller:
MCU:
Nucleo debugging
comm_can:
CAN communication
power_reg
12V to 5V power-stepping
Layout and physical interfaces:
X thermistors and Y irradiance sensors spread evenly across the topshell of the car and Z thermocouples wired to blackbody A.