ART-PI Sense HAT (Hardware Attached on Top) is a sensor expansion board suitable for the ART-PI development board and can be used to develop product prototypes based on display arrays and sensors.
The sensor configuration is compatible with the Raspberry Pi Sense HAT . The project will try to completely transplant the Raspberry Pi official Sense HAT driver library to provide users with the possibility to practice the Raspberry Pi official SenseHat experiment and Astro PI two space experiments on ART-PI .
The Raspberry Pi Foundation created a sensor experiment expansion board specifically for British ESA astronaut Tim Peake's first mission to the International Space Station. The name of the board is: Sense HAT, and the experimental project is called: AstroPi.
schedule
Programming reference
Components on the Sense HAT are connected to specific pins of the microcontroller and are programmed using the following pins: (Pin - Alias)
Attachment Engineering Framework Description
Project configuration
introduce
Since the PCB has a large number of pads and numerous components that need to be arranged neatly, I tried using a 3D printer to print a steel plastic mesh and a frame for arranging LEDs as auxiliary tools. Attached are the model files and print files of these two tools.
The stencil is to leave the solder pads on a piece of mesh to appear as "holes". The solder paste is scraped into the holes with a scraper, and then the stencil is taken away to leave the tin. If you use a copper needle to squeeze out tin by yourself, you can't squeeze out very small spots, and it's easy to squeeze out too much. Steel mesh doesn't have this problem. If the net is really made of metal, you can directly use a hot air gun to blow the tin into balls and leave them on the pad. This is called tin implantation.
The frame is somewhat similar to a steel mesh, with some LED-sized holes. Put the LEDs in the holes and they can be arranged neatly. Put the neatly arranged LEDs on the PCB at one time, use a desoldering station to melt the solder paste and reflow it.
The tool I use is Blender. After the model is exported to STL in Blender, the unit of 1mm (millimeter) or 1m (meter) will correspond to the 1mm of the 3D printer, and the Cura slicing software will automatically recognize it. For the convenience of editing, I am accustomed to using m as the unit in Blender (Blender displays the auxiliary grid in 0.1m units).
Export file preparation
In the PCB file of the project, there is a file of steel mesh and frame. This file is obtained from an ordinary printed PCB after removing unnecessary silk screens, wires, and frames.
Steel mesh and frame
Use the export tool in Lichuang EDA to export the top pad and silk screen layer as SVG files respectively. The actual size of the pad was measured in advance to be 63.5x38.5mm, and the SVG was imported into Blender to become the top-level steel mesh. In order to easily restore the true size, I added an outer frame to the exported SVG in Sketch and changed the size to 65mm x 40mm and 40mm x 40mm (Blender precision is set to 0.01, so the value is enlarged 100 times). I did additional processing for the silk screen. Close all the silk screen boxes into a square.
Here we only use the steel mesh as an example, and the framework is exactly the same as the steel mesh. Import the SVG file created in the previous step into Blender, and set the width and height to 65 x 40m (it will be 65mm x 40mm when printed).
Then expand the pad into an object, 5mm high, and expand the outer frame to 0.4mm high. Boolean operation, subtract the pad from the outer frame, and get a mesh with a thickness of 0.4mm.
Because the pads of the right sensor are too small, I decided to solder them separately, so I removed the three sensor parts on the right side of the actual printed stencil. The actual printed steel mesh and frame, in which I assembled the LEDs ready for welding:
After scraping the tin
Put the LEDs arranged in the frame on the PCB and solder them together. The capacitors and resistors on both sides under the frame have been placed and blocked. The sticky stuff on the board is solder paste.
After soldering, I washed the board and it was very clean with no excess tin.
Power on and test the components. The sensor has not been tested yet. The LED and button are both successful and there is no false soldering.
*For all device data sheets, see the attachment at the bottom of the page.
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