Workshop Update for July 9th, 2012

Today we finished building latest revision, and started testing the secret project firmware. We found a couple of bugs in our latest PCB design. The ‘DIR’ pin of the 74xx245 transceiver was connected to GND instead of being pulled high, and the ‘R/W’ pin of the LCD was left unconnected. We also organized in-progress projects for the next 6 months of projects.
We continued sourcing part suppliers for our part-kit. We sent parts lists to suppliers that replied to our requests on ebay.

We worked on today’s 3D model, and rendering. We also started the design of a Sick of Beige case for the ATX Breakout Board (pictured above).

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  1. Hardwiring the DIR pin wrong on the 245 is a mistake I easily can understand, I’ve done similar mistakes too many times during my 35 years of electronics tinkering. It’s all too easy to get the logic levels mixed up, especially on ic’s with both active-low and active-high inputs.

    But forgetting the r/w on the lcd on a pcb sent prototyping? You’ve must have had one hell of a hangover that day to miss that – or you’re getting sloppy because of the high count of prototype pcbs passing thru your desk during a years time. :-)

    Personally I’d love to read more about the mistakes and f*ckups that happens in your designs – it would be a great learning tool for most of us – it’s easier to avoid simple mistakes for your own projects if you have read about someone else doing them first.

    1. We post them as we find them :) The RW pin issue was more of a typo that went overboard :) We didn’t connect the trace directly in the schematic but instead used trace naming to connect them, a typo creased up on one side of the trace name, and unfortunately it got trough to PCB fab unnoticed, that is until Someone tried the LCD out on the new board.

      common mistakes are mirrored pin-outs, etc. Another one I remember was the Part ninja that had a totally non-functional battery power supply circuit for 2 revisions running… (a transistor was connected all wrong)

      1. Ah… named nets with spelling errors, that’s a nasty one.

        I almost got bit by that once as well, but luckily I caught it with the ERC. I usually don’t use the ERC because it spews too many warnings I really don’t care about like missing values, but that particular time I used it just for fun.

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