Obituary PCB

This is a functional artwork PCB for an obituary.

It was made in memory of our dear friend Obri, who has passed away way too soon on May 29 2020.

Artwork

Aside from the circuit itself (wherin lies the beauty of the PCB), the two logos of CCC Basel and CCC-CH are printed on top.

There is an empty area in the middle, intended for the obituary text.

For a rendering on paper, it is recommended to only print the F.Cu and Eco1.User layers.

Circuit description

This circuit is a simple LED chase with 6 steps, based on the NE556 dual timer and a 74HC273 8-bit register.

The LEDs are driven by six 2N7002 small-signal MOS-FETs that should provide ample current for a series of LEDs.

A 74HC32 quad or gate is used together with one of the timers to initialize the LED sequence. The timer generates an initial 750ms pulse that switches off after the sequence is latched into the register. To achieve this, it is configured for monostable operation, with the trigger connected to an RC circuit that will disengage after ~0.1ms.

The second timer generates the clock signal that shifts the sequence forward. It is tuned for clock frequency of 1Hz.

To change the clock frequency, three resistors need to be changed: R2 for the initialization pulse and R3 and R4 for the clock frequency. The initialization pulse should be roughly 0.75 times the clock period, so it switches off after the first positive clock edge.

If the initialization pulse must be shorter than 0.1ms, you also need to adjust the trigger pulse. Simply tune the RC circuit formed by R1 and C1 so its T value (= R · C) is roughly the pulse time.