BeagleBone Capes

After choosing the sensors and getting the software complete, we needed to create the sensor Capes for both BeagleBone Blacks (one on the float and one in the sub). For the BeagleBone Black on the float we attached the connectors for the stepper motors, the GPS module, a compass, a temperature probe, and a battery measurement circuit. The actual making of this cape took an unexpectedly long time, although it turned out very nicely:

The BeagleBone on the float has to be supplied with 5v. To do this we decided to use voltage dividers. This task took longer than expected as dropping the 25.6v from the battery had a few different issues. Originally we were going to use the LM317. This variable voltage regulator should have given us a constant voltage supply by choosing the right resistors (based on the formula). Sadly as the voltage supply to the LM317 dropped, so did the voltage output.

We then moved on and chose to use the simple UA7805 5v regulator. This chip can talk up to 24v and regulate it to 5v. As the rating on the 7805 was only 24v we decided to first step own the voltage using the LM317s we already had and then using the 7805 to get the exact 5v we required. Our float also needed a second 5v 1A power supply so we decided to create two of these circuits in parallel (as the chips can only handle a certain amperage). An image of the final regulator is below:

The second BeagleBone Cape we made is for the sub. This Cape is also fairly simple. It contains the MOSFET controllers for varying our LED brightness, the IMU, the depth sensors, the temperature sensor, and a few extra pin-outs for any future sensors. An image of the Cape for the submersible is below: