I came up with the LED heart idea a while ago and I've always wanted to make a PCB from scratch so I thought this would be a great opportunity to teach myself how.
I've documented the process a bit by taking photos and I'd like to share them with my dear readers.
Designing the Board
Board as seen on EAGLE.
First things first. Since the circuit isn't that complex I could've made it in MSPaint, but EAGLE makes everything so much easier and ensures you don't do odd stuff to your
circuit. After a few prototypes I ended up with this design and it looks quite elegant. The pads on the right are for the button cell lithium battery.
Laser printed circuit on glossy paper and a copper plate.
I ordered a single layer PCB plate online and bought the glossy paper at a local store. The PCB had to be cut into a smaller size, but since I don't have access to proper equipment I
had to use huge scissors normally used to cut tree branches. This explains why some of the edges look a bit rough. The ink must be transferred to the copper plate which is done by ironing the
glossy paper onto the copper for a few minutes.
Circuit ready to be etched.
The next step is to get rid of the copper layer except where the circuit's supposed to be. This was done by dipping the PCB into hot water mixed with sodium persulphate and moving it around with
a plastic spoon for some time. Once done I removed the remaining ink with acetone to expose the copper circuit.
Etching process timelapse.
Circuitboard after wiping the ink and drilling holes.
For drilling holes I used a Proxxon drill with a 0.8 mm head. Over 80 holes had to be drilled and this was
a drill I had to stabilise with my own grip, so quite the precision and steady hand was required.
The final components.
I started soldering the 8-bit shift register, ATtiny85 and power switch first. This way I could test each LED individually and check if the program's running correctly. The ATtiny85 runs
some code to animate the LEDs in a certain order. The 8-bit shift register was used to save some pins and made the circuit easier to design.
Soldering all LEDs and resistors.
Fancy close-up photo.
After a long session of soldering I managed to attach all LEDs and resistors with little to no trouble. The LEDs animated perfectly and it all looked pretty nice, but I still thought
there was something missing.
Outer casing made with SketchUp and a 3D printer.
The back of the PCB was exposed with sharp pins from the LEDs and resistor pins also stuck out like a sore thumb. I decided to design and 3D-print a casing for safety reasons, but also for practical
uses. For example, I attached a horizontal beam to the back of the casing so it can be placed on walls like a painting.