From fbf06fae2b196a842209ca6d05ef2ae6ac72f14a Mon Sep 17 00:00:00 2001 From: Gregor Riepl Date: Tue, 2 Jun 2020 00:37:01 +0200 Subject: [PATCH] Added readme --- README.md | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) create mode 100644 README.md diff --git a/README.md b/README.md new file mode 100644 index 0000000..0f85612 --- /dev/null +++ b/README.md @@ -0,0 +1,33 @@ +# 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 ยท C) is roughly the pulse time.