I am starting (actually restarting) an ambitious project for personal growth and fun.
I am building a scuba from scratch for use in the many lakes in my state.
I have a very good understanding of the physical building and operating principals of the sub itself, but I am struggling with the control system. I will outline my ultimate goals, with possible backup plans or workarounds. Any help on any of the subjects listed would be greatly appreciated!
The basic idea is to use PXFmini and Pi Zero in the sub, through ethernet tether to topside Pi Zero W WiFi repeater to Android or IOS running QGroundControl.
In the sub:
- PXFmini with power module
- 4C 3600MAH Li-FePO4 custom battery.
- Raspberry Pi Zero
Potential problem: Needs to be able to connect to ethernet tether. I have ENC28J60, but it needs SPI bus.
Possible solution: I have Pi 2 and Pi 3 available that I could steal from other projects.
- Pi Camera - I have both a regular and NoIR version. I don't know which will be better underwater. Will post back with results of tests.
- Pan / Tilt Servos - I don't know if 2 servos are supported in QGC.
- External /Topside Depth Sensors - MS5837-30BA pressure sensor. I assume I can connect this to the I2C bus on the PXFmini, but I don't know how to make it report in QGC, nor do I know how to zero the depth for lakes that are at +4000'. I have another MS5837-30BA that I can connect to the topside Pi Zero W, but I am not sure how to use that for automatic differential.
- External Temperature Sensor - I have an analog temperature sensor, and an ADS 1115 4 channel analog to digital converter. Same relative problems with the pressure sensor: Hook up to I2C bus? Report in QGC? Calibrate?
- Leak Sensor of some kind. Open to suggestions.
- (4) Brushed ESC to control 12V submersible bilge pump motors. This may have been a bad idea, but it is easily rectified later.
- 12V Ring LED light - I have a 5V relay module that could ?potentially? switch these from a GPIO pin.
- 4C 1200MAH Li-FePO4 custom battery.
- Raspberry Pi Zero W with WiFi
Potential problem: Need to setup as a wireless access point. Perhaps this:
Not sure if this can work.
Possible solution: I could use a laptop, but I don't want to be that close to the water, or pack extra stuff to the lake.
- Topside Depth Sensor - MS5837-30BA pressure sensor. I can connect this to the I2C bus on the Pi, but I don't know how to make it report in QGC (see above).
- External Temperature Sensor - I have an analog temperature sensor, and an ADS 1115 4 channel analog to digital converter for outside temperature. Same relative problems with the pressure sensor: Hook up to I2C bus? Report in QGC? Calibrate?
- Topside Battery Voltage Monitor - I would like to use the ADC and a voltage divider to monitor the repeater battery voltage.
Assuming that I can get some or all of the above items to work, it would be great to be able to use the QGC android app to control the whole thing.
Sorry for the wall of text as my first post.