PCB V0.1 errors and May 2024 updated Build Notes

[K7MDL2]

The first PCB produced had some small trace errors. The current version files are 0.4 and contain fixes for these and a few small new features like 12V on the Port A and B connectors.

For V0.1

1. The vertical segment 3.3VDC trace from the Teensy to J13 connector pin 1 crosses 2 signals to the Teensy. Use a sharp knife and cut the 3.3VDC trace in 2 places either side of the horizontal traces. Pin 1 is likely not ever used.

2. A 3.3VDc trace segment is missing supplying power to the 4 channel ADC (ADS1115) module connector. Solder a jumper wire between 3.3VDC somewhere on the board and pin 1 on J7. I found a via near the power supply section for the source.

3. The top and bottom ground planes areas and ground traces passing through them were meant to be "stitched" tying them together using via. The via were not assigned to GND circuit so in production they are all isolated and thus do nothing. The ground copper is floating. I scraped the solder mask away from select ground traces and vias in each area to tie the top and bottom together.

4. Related to above, the vias would also help transfer heat to the bottom of the PCB if they were actually connected properly. Further, the solder mask should have been left off this area to allow the option of bending a 7805 regulator down to the board and using the board and any metal under it to act as a heat sink. In practice, I add a heat sink to the regulator tab anyway and install a standoff under the tab & PCB to wick away some heat to the enclosure bottom or PCB support brackets.

5. The PCB was sized to fit a particular affordable aluminum enclosure. As of May 2024 it is unavailable. I could not find and exact replacement. Since most of the hardware is on the back edge, I recommend find a slightly larger case, 7" deep is good. Mount the PCB back edge to the back of the case (lot of holes to cut!) and on the front of the PCB leave off the power switch, LED, and PCB mounted USB/Enet combo jack. Instead run wires to front mounted LED and Power Switch. For the Ethernet jack, I just used the standard Teensy mag jack and ribbon cable that runs to the Teensy 6 pin connector. I turned the jack upside down and soldered the jack case to the PCB ground plane. facing out to the side where I had lots of room. In my 2nd build I used a 10" wide x 7" deep Hammond model 1402KV enclosure. I mounted a 3.5" Nextion touchscreen using a CN milled acrylic bezel on the front panel. I used a right angle ethernet extension to chassis mount on the back panel. Same for the USB jack.

[K7MDL2]

[K7MDL2]

I later added a heat sink tab to the 7805, a chassis enet jack on the back panel, and hex standoffs to support the edges of the ADS1115 and ADL5519 modules. I use 1 washer on each SMA jack between the back panel and the ADL5519 board. Ensure you have some clearance around the RC and D-Sub connectors as needed for proper connector seating clearance. Still to add is a rear panel chassis mounted USB extension for the Teensy. Really only need this for dev convenience if using ethernet.