Proposal¶
What does it do?¶
As a final project I want to build a heliostat to continuously reflect sun to a predetermined point. In the principles and practices week I described why I choose this project and what a heliostat is.
My future goal is to build a heliostat to reflect sun from the neighbors roof into our garden. For my final project I will make a desktop version which is small enough to carry around. A fully working desktop version will be a great starting point to build a bigger and waterproof version in the future.
Who’s done what beforehand?¶
I didn’t find any previous Fab Academy heliostat projects. I found some related projects like sun trackers and solar cookers. These are a few of them:
I found the Open Sun Harvesting Project whose aim is to make advanced DIY sun tracking and heliostat projects more accessible to the general public. That sounds really interesting but there hasn’t been any activity in their github repository in the last years and their website is not working anymore.
I found 2 consumer heliostats:
It’s not clear if it’s still possible to buy them and I didn’t find any detailed information on how they work. My heliostat will have similar functionality to theirs but my reasoning, designs and programs will be open.
What did you design?¶
- structure
- electronics mount
- gears
- leveling feet
- motor control PCB
- I developed the motor control / mirror positioning program
- I developed the web user interface
What materials and components were used? / Where did they come from? / How much did they cost?¶
| Part | Model | Price | Quantity | Origin |
|---|---|---|---|---|
| Turntable bearings | generic | 25 € | 2 | Amazon |
| Stepper motor | 17HS15-1504S | 10 € | 2 | omc-stepperonline.com |
| Stepper driver | SilentStepStick TMC2100 | 10 € | 2 | lab/digikey |
| Acrylic sheet | 1 m2, 5 mm thick | ~60 € | 1 | lab |
| Acrylic mirror | 40 x 40 cm, 3 mm thick | ~20 € | 1 | lab |
| 3D printer filament | PLA | ~5 € | - | lab |
| Electronic components | Microcontroller, headers… | ~10 € | - | lab |
| Screws | M3 and M5 | ~5 € | - | lab |
Total ~190 €
What parts and systems were made?¶
- I laser cut and assembled the structure
- I 3D printed the electronics mount, gears and leveling feet
- I milled and stuffed the motor control PCB
What processes were used?¶
2D and 3D design, Electronics design, PCB fabrication, Laser cutting, 3D printing, embedded programming, application programming
What questions were answered?¶
- Figure out options to determine the sun’s position. In my final project I will use a library to calculate the sun’s position rather than a sensor to detect it.
- Figure out options to keep track of the mirror position. In my final project I will orient the heliostat towards south, level it and home the steppers at startup.
- Relationship between axis rotation and mirror orientation. More details can be found here.
What worked? What didn’t?¶
- It was more difficult than expected to find the relationship between axis rotation and mirror orientation. I didn’t manage to find a geometrical solution but I found an alternative
- I made a real world test and it worked :-)
How was it evaluated?¶
- It should be possible to configure where the heliostat should reflect to
- It should be possible to run the heliostat in AUTO mode where the mirror is automatically adjusted based on the sun’s trajectory to keep reflecting to the same place