NOTE: GHOSTLY LIGHT V1 is not recommended for use. There is nothing wrong with this design, but due to the short battery life and its current requirements, its use as a toy or desk decoration is severely restricted. The current consumption can reach 200mA below 2V, which for this type of batteries is out of specification.
Ghostly light is a small toy project powered by a coin cell, which is inspired by the ghosts of the classic pacman game.
This small toy consists of a plastic shell designed to be 3d-printed, a specific hardware, and a software that generates the different effects.
The plastic shell has the shape of a pacman ghost. It consists of two parts, which allows you to remove the PCB and change the battery. It's recommended to print in translucent neutral color to get a better finish.
The hardware consists of a low power step-up, an ATtiny85 microcontroller and an WS2812B addressable LED. All the pins of the microcontroller are exposed in a header, which makes this PCB also ideal as a development environment for this microcontroller.
When the toy is turned on, it will randomly choose one of the four pacman ghosts. Once (automatically) selected, it will show different animations over time, which are also randomized. The toy does not require any type of interaction with the user, being ideal as a decorative element.
This project was originally conceived as a gift to my friend Isi, and developed as a thank-you present.
Still, you're free to reuse this project for whatever you want, even if it's as shabby as decorative lights or as a gift to other people, knowing they'll never be as cool as my good friend. If you are only going to use the hardware of this project as a development environment for your own applications, make sure they are inclusive and creative. Do it for my friend. Thank you and happy hacking.
For the printing of the plastic shell, it is recommended to use transparent or translucent filament of neutral color. I have used transparent PLA. After some tests, I have achieved the best finish with a maximum layer height of 0.2mm, non-linear infill pattern, such as Slic3r-PE "Archimedean Chords".
The transparent filament often gives first layer adhesion issues, and since the shell has few contact points on the bed, print may fail. For this reason, I have tried to find the parameters that have worked for me to achieve first layer adhesion and be able to print the shell:
- Bed temperature, 70ºC first layer, 65ºC other layers.
- Two first layers without layer fan.
- First layer speed at 35%.
- Reduce speed to 75% manually to a height of approximately 10mm, restore to 100% after this height.
- 120% extrusion width (flow) in first layer.
- Lower the Z-offset 50µm (carefully modify not to block the flow of the nozzle or damage the bed!).
Even so, if the problems persist, I have also generated a plastic shell file ghost-aid.stl with a perimeter ring, which should give much less adhesion issues. In return, you have to cut the surplus once printed. Alternatively, you can add as much brim as you like.
You only need to print a copy of the ghost.stl and ghost-cover.stl files. No support structure is required for any of the files.
The electronic design has been made in KiCad EDA, providing a small step-up regulator with on-off switch, power from a coin cell, an ATtiny85 microcontroller with a large breakout header, and a WS2812b addressable LED.
The power supply unit, starting with a button battery (BT1), goes through a step-up in order to provide 5V during the whole range of battery discharge, down to 0.9V. This step-up is based on the TPS61070 (U1) and requires very few component count, a small footprint and high efficiency. Its peripheral components are limited to a bulk capacitor at the input (C1) and at the output (C2), a voltage divider for output feedback (R2 and R3), the coil (L1) and a pull-down resistor (R1) for step-up enable, which is used to turn the system on or off by the switch (SW1), remaining disabled and in low power state when it's off.
The control is performed by an ATtiny85 (U2) microcontroller, with all its pins exposed on a header (J1) for use as a development board. The microcontroller has a pull-up (R4) for the ~RESET pin. It also uses only one pin to control the addressable LED (D1), while another unconnected pin is used for analog readings and to serve as a seed for random numbers. The addressable LED, centered on the board, has a decoupling capacitor (C3) to stabilize its operation, given the high current requirements of this element.
All discrete components have a 0603 footprint where possible, maintaining a small space but still being possible to manipulate them manually.
The manufacturing files are located in the out folder:
- BoM & CPL:
ghostly-light.xls - Gerbers files:
ghostly-light.zip
The board is also intended as a development environment for ATtiny85 with a reduced form factor and coin cell powered. All microcontroller pins are exposed at the header. The board can be powered externally via the header, as long as the switch is in the off position, without damaging the regulator (see this post from Texas instruments technical forum).
NOTE: No battery life calculation or load adequacy has been performed for this battery. The circuit consumes an average of 40-50 mA.
The code has been made in C for Arduino, for a Digistump board, since it has better support and compilation optimization than other packages with support for the ATtiny85 microcontroller. All the code is extensively commented and documented. Also attached is the compiled binary file.
The compilation has been done with the following software version:
- Arduino IDE 1.8.4-linux64
- Compiler: avr-gcc 4.8.1-arduino5
- Library: Adafruit_NeoPixel 1.1.7
- Board package: Digistump AVR Boards 1.6.7
- Carry out the assembly of the board with all its components. It is recommended to first assemble all of the top side, then the battery holder and finally the header. Three or four unassembled PCB can be used to hold the pins in position while soldering.
- Using the header, and with external power, first burn the fuses of the microcontroller and then upload the program. It should start working. An AVR programmer is required.
- Remove all cables from the header and insert a coin cell. Make sure that the battery has correctly inserted into its position and with the correct polarity. When you turn on the board with the switch it should start to work. Switch off.
- Place the PCB over the printed cover. Only fit in one position, with the battery on the underside and the header on the corresponding side.
- Place the shell on top. The hole for the switch on the rear side must be aligned with the switch on the PCB. It may be necessary to remove any unwanted burrs and reliefs from the inside of the shell.
- Lower the shell until it almost closes. Press the shell down until it clicks into place.
To remove the PCB, use a thin element to lever out the cover on each of the legs of the shell.
Copyright (C) 2018 kwendenarmo. This file is part of Ghostly Light
Ghostly Light is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.
Ghostly Light is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details
You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.