January 23, 2007
PIC shakeup, PCB sent-to-the-ether
The BlimpBot's schematic has been translated into a PCB layout, and the layout send in for production to expressPCB.com. I sent them the design above, and an actual circuit board will arrive here Friday. There was of course a little money involved too.
Given the short timespan allotted to actually designing the PCB and reworking the schematic (as discussed below), I am crossing my fingers that it does not contain any big mistakes. Time will tell...
UPDATE: The PCB design underwent 2 revisions subsequent to this one. See newer PCB-related-posts for details. Here is the final design.
In other news, we skirted a near-disaster with the original schematic...
On Sunday it was discovered that the microcontroller used in our original design (i.e. all of the schematics below) is a bit insufficient. The short story is that it was only capable of controlling one of the three motors on the blimp. The only alternatives we could find were bigger -- 40 pins versus 18 -- overkill for what we want. Plus, each extra pin means more solder, more square area of PCB, and more weight, all of which are detrimental to miniature helium blimps.
But some more searching revealed the Microchip PIC18F1330, a brand new model with only a slightly incremented part number. This one can do just what we need -- control 3 independent PWM outputs. So the new PIC was added, the schematic revised, and the PCB design laid out, all since Sunday night.
Posted by jrpowers at January 23, 2007 01:57 PM