boloblinky

thingiverse

I originally created this swag bag tchotchke for my 11-year-old son's birthday party, where it serves as a fun way for kids to build and learn about soldering, micro-controllers, programming, and making things. To make it easy and affordable, I set two design parameters: the project had to be simple and cost no more than €10. It ended up costing €9.81, including the PLA case and 4 batteries. I chose the nano and max7219 because I've used them before and knew they have user-friendly libraries that would simplify the process. Plus, both could be purchased for under €3 each, leaving around €4 for other parts. The code is available on https://github.com/leidentech/boloblinky. The program has several functions that can be accessed by long-pressing the left or right button: * A 6-sided die rolls when either button is pressed. * A magic 8-ball type random advice giver responds to either button press. * An image editor lets kids go through the matrix pixel by pixel with the left button and turn it on or off with the right button. Long pressing either button displays the final image. * A race game navigates randomly generated roads when using the left or right buttons. * An eyeball animates, blinking and spinning in crazy ways. * A timer counts down a minute by lighting up a pixel per second. The race game is similar to one of my first programs on the Sinclair ZX81 from a long time ago. It also reminds me of the Mattel Electronics games I played in the '70s. Other ideas were considered, but since there are only two buttons, possibilities are limited. Build To assemble the device, use OpenSCAD and STL files found in the case directory. There's an alternate design with micro switches inside the case, but my son preferred them on the outside. Battery Case: Place battery ends in the case so that the spring is at the end nearest the square plug bracket at the end where the switch is. Wire the nearest spring end underneath the bracket to the middle pin of the slide switch. Next, wire the nearest pin of the slide switch to the (-) end of the two-pin plug passing the wire underneath and through the bracket. Switches and Nano Wiring: Attach two wires with female plugs to the GND/VIN on the Nano next to the RST pin. Wire the two pins nearest the bottom wall on the switches together, and the two upper pins from the switches together. Then, connect the middle pin on the switch nearest the Nano to D2 and the middle pin of the other switch to D3. Connect the remaining pin on the switch nearest the Nano to GND next to D2 on the Nano. Finally, wire the remaining pin on the far switch with a female plug to go into the GND of the max7219. Now, connect (with female plugs) the Nano's D10 to go to DIN on the max7219, The D11 to go to the CS pin on the max7219, and D13 to the CLK pin on the max7219. Connect the 5V pin on the Nano to the 5V on the max7219. This wiring corresponds to the nano code and the libraries used. Plug all wires into the max7219 correctly, then place it in the opening flush with the face of the top. Bend pins as necessary to make a tight fit. Next, slide the Nano into the slot so that the USB port sticks out of the provided hole.