The goal of this project is to design something using a PCB of an area of a square inch only and to learn KiCAD. I decided to go for Atari Punk Console, because the circuit is not that complex and the components can be easily fitted on a square inch PCB. PCB was designed using KiCAD. Atari Punk Console utilizes two potentiometers to control the frequency and the width of the pulse. A passive buzzer is connected at the output that generates sounds relative to that pulse. The potentiometer can be replaced by temperature or light sensors.
For designing a square inch PCB, I was considering the two PCB designing softwares: Eagle and KiCAD. I chose KiCAD because it is free, also my goal was to learn KiCAD, not just to design a PCB. Initially all my components were THT, but had to replace the 555 timer ICs to the surface mounted ones eventually because of small PCB size.
I used a 2 pin connector for power and two 3 pin connectors for potentiometers, so we can connect other sensors, such as LDR, in place of the variable resistors.
Noticed the two holes above the buzzer? Those are to mount the PCB on something easily (for example, a toy)
On KiCAD, it is so easy to manage the layers and view. KiCAD even has a 3D viewer which Eagle does not have.
Front and Bottom View
A PCB this small and this simple can be easily manually routed, however when we get to much bigger and much more complicated PCBs, autorouting is the best and the safest option. BUT KiCAD does not have any stand-alone autorouter, however we can use several external auto-routers to route any PCB. I used FreeRouting available at FreeRouting.org. Here are the steps involved.
1) Download the FreeRouting jar file
2) Generate and read netlist
3) Export Specctra DSN file in Pcbnew
4) Open the DSN file in FreeRouting
6) Import the saved autorouted specctra session file in Pcbnew