Decora “Smart” Switch P2: Hardware Oops

The next step was creating the hardware.

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I’m blue. I’m purple. If I was green I would die.
Screen images may be simulated.

The main thing was the buttons. so I designed a contact pad for membrane buttons to go on.
However, I really hate using wireless so I decided to use (UART over) a RS transceiver. I decided to put in a THT (8DIP) for ease of soldering. RJ connectors are easy to use, and (relatively) cheap. Plus, most an 8P8C connectors are designed to crimp to cat5 wiring which should give me less interference. I have 2 pins for TX plus 2 pins for RX as well as 4 more pins which I plan to use for GND, 5V, and 12V. (two pins for ground)

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Board schematic. Click for larger.

Pretty simple. As long as I can fit it in the allotted space that is. With the mounting holes, things can get a bit tricky, but it wasn’t too hard.

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My name is Swiss Chez.

I cut some buttons out of a dollar store calculator to use for the membranes, and it worked well.

I grabbed a crossover cable, hoping that I had wired it correctly, and tested the transmit/receive pair from one board to the other. Unfortunately, the transmit/receive pair didn’t seem to be working. Clearly, I had done something wrong. After a few hours of great confusion, and consideration for the chip behavior, I checked my order and found that I had ordered a dual transmitter. Instead of the SN75179B I had meant to buy, I somehow got the UA9638CP. I think I had them both in the cart, because I had another board I was considering and I just removed the wrong one. This is why, even if you are literally only getting two items for your board you should create a BOM and double check it.
And then it was the holiday season and I didn’t have time to play around any more. I might get back to it eventually, but it isn’t a high priority right now.

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