Board to board communication and power supply

Three weeks ago a prototype of the power supply board was milled at NTNU, and the last few days it has been tested thoroughly.

Picture 1: Power supply prototype

The microcontroller software is pretty much finished, and board-to-board communication has been successfully tested with another microcontroller running as an I2C-master, as can bee seen in the picture below. More specifically, the power supply will send information about voltage levels and current draw to the main board, which in turn will be sent down to the ground station and displayed on a monitor.

Picture 2: Successful test of communication between PSU
prototype and I2C-master on breadboard

It all seems to work well, although it needs some serious testing over long durations before it is considered stable. The heat dissapation has been tested under maximum loads, and the temperature seems to be within an acceptable range.

Professional PCBs are being made in China right now, so the prototype seen in the pictures above will be replaced in near future. The final PCB layout can be seen below:

Picture 3: Final PCB layout

Stay tuned!

Some calculations

In NX we have now modelled all the induvidual components. This provides an effective way to let us tweak the design to get the optimal use of space, and optimal weight distribution.




Calculations for insulation demand is also a crucial part for this spacecraft. On the journey the craft will be affected by temperatures down to -60 degrees celsius. We must make shure our materials can keep their mechanical properties. And we must ensure that the electrical components is sufficiently insulated. The body will be made of plastic-foam with good insulation properties. The electrical components generate heat, about 15-20 Watt for our craft. This means that the insulation should not be too large either, since the electrical components need some cooling aswell.


Calculation for the wing-profile is hand calculated, and supplemented with aid from X-foil and Foil-sim. The wing will be made in plastic-foam, reinforced with carbon tubes, and coated with fiberglass.

EOS2 Sensor board

The first revision of the sensor board is completed, and is ready to be milled and tested. This board contains on-board temperature, humidity, absolute pressure and differential pressure sensors. In addition there is a connector for external temperature and humidity sensors. The differential pressure sensor is used to measure air speed with a Pitot tube.

The sensor board will interface with the other EOS2 boards via the EOSEFF header, which contains power and an I2C bus connection. More information on the sensor board can be found at the wiki.

https://wiki.edgeofspace2.com/wiki/sensorBoard

Airplane Design

Hand sketches of the airplane design. 

Airplane characteristics are now calculated, and the design is chosen.
The main focus of the design is to get an airplane that is stable, and can manouver in low density air. The solution is a glider plane with a pusher propeller. With a pusher design, we will ensure the field of view of the camera is not blocked by the propeller.

3D model of the airplane design. 

We want to use some of the aspects from gilders, such as self-stabilizing dihedral wings and large lift. The wing span will be approximately 2 meters and that should give us enough lift to support the payload. Most of the design has been based around the payload box and what we want to put inside the airplane. The circuit boards are stacked on one plate so that we have a modular design that will support all the circuit boards that's required.

Stacked circuit boards within the airplane body. 

We also have room for two cameras, a parachute, radio transceiver and the pusher propeller. The motor for the pusher propeller will be partly inside the body to account for the low temperatures in the upper stratosphere. 

Pusher propeller motor inside the airplane body. 

We have decided to use styrofoam for the body because of the good insulation properties. We are also working on a heat model to make sure that all the components inside the body will be working in their operating temperature range. It will be posted soon.