To design the LifeLinker various design programs and manufacturingmethods were used, they will be briefed here. The Lifelinker design process were: schematic design, circuit design, 3D box design and microcontroller firmware programming.
For the manufacturing were used a 3D printer, a manual stencil printer, SMD oven for circuits and a laser cutter.
The schematics and the PCB design were made using the software Altium Designer, due it’s what i use at work and I’m used to it, but I could used Eagle easily for this circuit.
One advantage to use Altium is that the component library that I use is made as an Acces database, what let me have more control over the components. I add various data about voltage, current, number of pads, supplier codes, datasheet links, stock and warehouse location, etc… This let me generate BOM’s with prices from suppliers (Farnell, Mouser, Digikey..) and their stock
In the schematic we could see that it has a 8 bits microcontroller STM8L151, a rotative encoder, the power supply to generate 3V from the batteries, the 7-segments display with three digits, 5 leds to show the current mode and a buzzer. The microcontroller is fully maximized, it hasn’t a free pin, and from the 8kB of flash it has, the code uses 7.5kB
The PCB is simple, with two faces:
The prototypes were ordered to Elecrow with the solder stencil in 15x15cm. The cost of 10 PCB’s + shipping + stencil was only 30€, being a very low price. The solder stencil allows to make the soldering with a SMD oven and achieve a very professional result, also allows to mount some components with pads underside.
The solder stencil ordered with the PCB’s was used to mount all the MSD components. This stencil has 15x15cm and to solder all the circuits I made a wood framework that could be used in other projects:
To make the box, the 3D design of the circuit was imported to Solidworks and the box was created over it. The box is made to be printed with a FDM 3D printer. The rear cover is laser cut and fits by sliding it in some slots in the box.
Front cover design:
To make the front cover design I choose a Magic card, due this device is mainly thought to be used in this game, although is perfectly valid for many others. The box proportions are from a scale froma a Magic card, so I used the web Magic Card Maker to make a simply design and print it in adhesive vinyl. Later I redo the drawing adding text and the picture of the circuit in the card.
Programming the firmware:
The microcontroller is a 8 bits STM8L151F3 with 16MHz, 8kbytes Flash and 1kbyte RAM. To debug the code and program the prototypes I used the evaluation board STM8L-DISCOVERY and as compiler the CXSTM8 from Cosmic Software, it has a free license for the STM8 microcontrollers. As IDE I’ve used the ST one, STVD (ST Visual Develop). The code could be checked at Github, https://github.com/microhenrio/LifeLinker.