Friday, March 8, 2013

Added a PCB for the Alarm Expansion Card

*UPDATE* I wasn't able to test the board for a while after posting this, but have since had an opportunity to solder the components together, code the Arduino, and make things happen.  I'd call that a success!

During a debugging session for Project Homebrew Security System , my cheap soldering/protoboard setup failed on me (try disconnecting and reconnecting things often when installing a garage door opener switch and having those fine cat5e wires break).  I started looking at doing a PCB instead of a heavily soldered prototyping board.  I ran into BatchPCB, and opted to create a board (it was cheap enough).

I knew at some point I wanted some analog sensors in there, at least one switch for the garage door opener, and possibly another one (for future expansion).  Using Eagle, I threw together a schematic with two radioshack relays and three headers (the big one attaches to the Mega, the small one is supposed to be on one end so that it can be soldered onto an analog extension if needed that will work on the left side of the mega board) and the medium header is to be connected to the inputs :

You can get the resulting Eagle schematic here.  Once I had that, it took some working to get it to the right size and position, but I managed to create an Eagle board (http:/, then created the Gerber files ( using a nice Hackaday post, and uploaded it to BatchPCB.

After placing an order (and expediting it), on Mar 26, I received the results of the BatchPCB boards.  I made a mistake on them and got the ground/5v+ points on the board wrong.  Additionally, I found I had tied pins 50-53 to the switches - a bad idea if you wish to use the SD card on the Arduino Mega.  I have now updated the PCB.  Even with my foo bar, I must say that I am definitely impressed, and suggest anyone needing some professional boards done go through BatchPCM (and especially their supplier).  Here's what I received :

The resulting boards had a great finish, and the components fit pretty accurately.  The only gripe I had was that the area that the relays fit into had smaller drill holes, which caused it to be a little snug, but it did fit without a lot of force.  Installing components (almost all, missing a male-male header for the top end, will pick that up today) went quickly once I fixed my soldering iron, and it connects right up to the  Arduino mega :

All in all, I'd say that is a successful PCB!    I did solder it together, and ran into a few issues, but ended up updating the PCB listed above with the flaws corrected.  I also made some changes to the code because of some upgrade issues with the Arduino IDE.  The next step was to connect it all together, update the code once more, and give it a test.

No comments:

Post a Comment