Tuesday, 7 October 2014

ATTiny85 Shift Register – Etched Boards

Okay, so I’ve etched the boards for the ATTiny85 + Shift Register and the LED + Resistor sub-board.

ATTiny85 and 74HC595 - Etched

This is the main board, top left is the ATTiny85, middle is the 74HC595 and the row of 9 pins at the bottom is the interface to the sub-board.

This went fairly well, I tested all of the traces and found that the board measures up OK.

LED Sub-board - Etched

And, above is the sub-board with LED and SMD (0805) resistors coming in to two pin headers (4 pin and 5 pin) for the interface to the main board. As you can see in the picture, there is some misalignment in the transfer. This happened because I needed to overprint the board (the first run with toner transfer didn’t work very well). It also lead, more seriously, to three points on the board where the misalignment resulted in bridging. All of the bridges occurred on the SMD pads. I cut the trace with a scalpel and the scraped off the copper to make sure that the bridge was removed.

After testing the modified/corrected board with the multimeter on continuity, I found that I had eliminated all of the bridges and there were no gaps in the trace that would cause the board to fail.

Next, I’ll be drilling and filling.

Finally, here’s another 5V regulator (LM7805) circuit with a power indicator LED and resistor.

5V Reg with LED - Etched

This is just the same as the last one with two modifications:

  1. I’ve added a second set of pin headers to improve the mechanical stability of the board when it is plugged in to a solderless breadboard; and
  2. LED and resistor (far left in the above image).

Well, that’s it for tonight. Good luck and happy soldering!

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