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Components research
This page presents the method and outcomes of the search for relevant components, in the prospect of future developments. We have been investigating:
- Battery Management System (BMS): battery charge & discharge + status display
- Environmental sensors: temperature , pH, salinity, oxygen, luminosity, sonar
- Add a lamp, allowing for better images
- Have an adjustable camera depth, for investigating corals in murky waters or get higher-precision pictures
Input: LiPO 10Ah-25C 14.8V 4S 148Wh
Needs:
• charge & discharge management system (BMS)
• battery status display
We could have chosen a fully integrated BMS fulfilling both functions. Though practical and maker & user-friendly, they are under backlash for their poor reliability, short lifetime, and high price. We will thus use two separate components, working together for a hassle-free drone battery.
BMS: Need for a system of battery charge & discharge management, to ensure long lifetime. It needs to be adapted to the number of battery cells (4S), as well as to the charging voltage (16.8V), and the current (10A). Finding the precise model is the biggest struggle.
- BMS 10 cells, 10$ on Alibaba
- BMS 4 cells, 8.50$ on Alibaba (Min. order 5). Looks like good quality, would recommend.
Display: need to display the battery status & charge, and same reqs as for the BMS : has to be adapted to battery type, voltage & current.
- LCD screen pre-programmed for various modes. 3$ on Alibaba
Input: 5V sensors, waterproof/compatible
Needs: temperature , pH, salinity, oxygen, luminosity, sonar
Fully integrated solutions are available on the market. They are user-friendly and render high quality & quantity data. However, the price is quite high, up to 5,000 USD (Source). We thus opted for separate sensors, allowing us for more flexibility, and a lower cost.
Temperature: the sensor needs to be waterproof if we want precise and accurate results. Otherwise, an in-drone sensor could’ve been chosen, taking away the waterproofness constraint, however it can only measure an averaged temperature (thus less precise), and can be fooled by internal heat dissipation (thus less accurate).
- Stainless steel waterproof temperature probe 5V, 1$ on Alibaba
pH: the sensor is waterproof by definition, as it measures liquids. However, there are three strong constraints: maintenance, sensor calibration, and operation conditions.
- Maintenance: the sensor should always be in a saline solution, in order to protect its ultra-sensitive electrodes. It means that the design of the drone should allow for inserting a small plastic container around the sensor, when not in operation.
- Operation conditions: pH sensors are very sensitive to contaminants. It should thus be protected by a filter, in order to avoid biofouling and physical damage. This is opposing to the ‘easy access’ constraint.
- Sensor calibration: pH sensors need to be calibrated before each use, to ensure accurate measurement. We thus need again an easy access to the probe. Also, in involves having buffer solutions, and waiting for a few minutes for the drone to be calibrated. We have three solutions: • use a ocean-compatible pH meter (expensive) • hack this ocean-compatible pH meter and create an open-source low-cost one (cheap, but time & labor expensive, + unsure success) • go without a pH-meter. Products:
- Handheld waterproof pH sensor, 14$ on Alibaba
- SeaFET Ocean pH sensor, ~1,000$ ? (Use in research)
- Arduino pH sensor by Gravity, 30$
Salinity: the sensor is waterproof by definition, as it measures liquids.
Oxygen: the sensor is waterproof by definition, as it measures liquids. However, the sensors avec very expensive, around 100$.
Luminosity: the sensor needs to be waterproof.
- Waterproof sensor with control module, 10$ on AliExpress
Sonar: the sensor needs to be waterproof. It must also range up to 20 m, further than this isn’t required as corals mostly thrive in the 0-20 m depth range. No other specific constraints.
- Arduino waterproof sonar JSN-SR04T / AJ-SR04M, 4$ on Aliexpress