Our onboard electronic system is split into 4 parts:
- Power Supply
- Data-Handling PCB
- Exchangeable mini-PCB’s
- Reference Sensor PCB
The sources (as far we are allowed to make them public) are available on GitLab: https://gitlab.com/groups/fovs.
When soldering electronics for use in a harsh environment such as space, special care needs to be taken. It is very important to solder every pad just once.
The power supply PCB is the electrical connection between the REXUS Service Module and our main PCB for data-handling. It provides
- ±5V and +3.3V power
- Optocoupling of LO, SOE and SODS signals
- RS422 to UART TTL conversion
The Data-Handling PCB is the heart of our electronic system. It carries the microcontroller that is used to read all the sensors, saves the data to an SD-Card, communicates with the ground station, and does some other house-keeping tasks. As highlighted by the block diagram below, it contains multiple temperature sensors, ADCs that measure the optical signals, and connectors, e.g. to the reference acceleration sensor.
The mini-PCB’s are equipped with the opto-electrical chip, a transimpedance amplifier and a 2-stage, multiple-feedback, active filter. This provides us more flexibility to fit the filters to the optical chips, and to exchange damaged parts in case that’s necessary.
To get a plausibility check of our acceleration data, an electrical sensor is mounted directly above the optical sensors. This PCB is populated with an ADXL312 acceleration sensor and LM73 temperature sensor, and communicates to the main PCB via an SPI bus. Features of the acceleration sensor include:
- Acceleration range: ±12 g
- Wide temperature range: -40 to 105◦C
- Measurement rate: 3.2 kHz