Tuesday, 7 October 2014

ATTiny85 Shift Register – With Sub Board

Breaking the design of the circuit into a controller board and LED sub-board arrangement seems to be a bit … inefficient. Of course, this could be just because of my design.

Fritzing - ATTiny85 - Shift Register - 3_pcb

On this board there are just the ATTiny85, 74HC595 (Shift Register) and the necessary pin blocks for connecting it to the round LED sub board. There’re probably more efficient designs for this, but I’ve simply removed the LED and resistors and then re-routed the traces.

Fritzing - LED Sub Board - Round_pcb

The LED sub-board is probably more like what I wanted. At the moment, the 9 pin headers are aligned for main and sub-board simply connecting using a straight forward pin block pairing. However, I’m likely to connect the main and sub-board with jumper wires rather than male pin block to female pin block, so the arrangement of the pin headers on the main board are kinda irrelevant and I could make the design more efficient on the main board, for instance, I could have the pin header right up against the 74HC595, meaning that the routing would be much less of a dogs breakfast. That would also mean that I could re-orient the ATTiny85 and have the traces from that to the 74HC595 more straight forward too.

With that in mind … the arrangement of the main board should probably be more like the following.

Fritzing - ATTiny85 - Shift Register - 4_pcb

This is a much more straight forward design and doesn’t waste any space. The new design (above) is 40mm x 40mm, so I can save a bit of space using this layout rather than the one above. 1 wire to carry the GND and 8 for the Q0 – Q7 pins on the 74HC595 chip.

That should probably cover the design side fairly well. OK, so this is the design that I’m going to go with.

I guess the other thing that I like more about this design is that I can have a couple of LED sub-boards with different coloured and sized LED and play with the visual design of the board more.

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