Friday, November 21, 2014

The PCB Part 1: Layout

Along with preparing the form for casting, I've been working on the electronic side.  As mentioned, I plan to go with LEDs.  Rather than using a typical project board to lay them out, which would require a much more soldering as well as cutting/stripping way too many jumper wires, I figure I'd go for a custom PCB.  

Since this is truly a one-off PCB, it doesn't make sense to send it out to be made.  Even one of the discount makers, with the required order minimums, isn't cost effective.  

Plus, I've been wanting to try to etch my own PCBs for a while using the toner transfer method. I'm following advice from several methods from the Internet but I'm sticking closest to the write up on the Robot Platform website.

The first step is to create the layout.  I came across this really neat layout program called Copper Connection written by David Cook.  It is an excellent little program!  It doesn't have the advanced features  (such as auto-routing, circuit analysis, etc...) that some other packages may have but it is exceptionally simple to use.  And for this project, it was perfect!  I highly recommend it, check it out at Mr. Cook's website Robot Room.

After a few minutes to get up to speed, and one revision change after deciding to use a different type of LED, I was able to layout This circuit will include the tail lamp (i.e. the light that is on when the headlight is on) and the stop lamp (aka brake light).  I wanted to incorporate turn signals as well but felt that would be too complicated for a single-sided PCB.  

Here's a quick shot of the layout showing the top silk screen (which won't be used in the final PCB) and the bottom copper layer.  

Keep in mind, the bottom layer needs to be backwards because it will be transferred to the actual PCB.  One of the great features of Copper Connection is that it allows you to layout a component as a stack on all layers at once.  Then, when it comes time to print the PCB, depending on your selected transfer method, it flips the appropriate layers as needed.  This is especially useful after having a few beers, when your spacial orientation ability is not where it should be.

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