Step 6: PCB Design
Drawing the Circuit Board
Using Adobe Illustrator I created different layers for the traces, components, the grounding plane, and the part labels. Using the component's data sheets as reference I then drew out all the components to their actual size and arranged them to fit within a 37mm diameter circle. Traces were drawn according to the schematic to connect the components.
I used Illustrator because I am familiar with it, but the most common way to design circuit boards is Eagle PCB, a free software from Cadsoft . This program can be used to draw out a schematic that can be converted into a PCB layout. The designs and files that it generates can be printed out or sent to a manufacturer to be fabricated.
Charge LED, I'm Doing it Wrong
While designing this PCB I had assumed that the MAX1555's charge LED should be connected to ground. After I had finished soldering I did some testing and found that the LED wasn't doing anything. It should have lit up when the robot was connected directly to a USB port and the battery was charging, but that didn't happen. Turns out the LED should have gone to +V...
To fix this I desoldered and lifted the LED's lead, the one that I thought went to ground, from the PCB and connected it to +V with a jumper wire above the board. I stuck a dab of hot glue under this LED to make sure the lead didn't touch the ground pad. This error was corrected in the schematic, but I have not fixed it in the PCB layout. Instead I've just shown the jumper wire.