End-of-year project (2022) for the ElektroClub.

In my village I'm volunteer for an "ElectroClub" for children 8 to 12 years. At the end of the (school) year we try to have a master piece for them, to remember the club. In 2022 we wanted the year digits with flashing numbers; this is actually a copy of an old project:

What we remembered from 2014 is that creating the wooden panels, soldering all the LED wires, and gluing all wires in place, was too time consuming. This year we will try a variation: designing the PCB using EasyEDA and manufacturing it via JLCPCB. The biggest challenge is to get a nice rendering of the big digits 2022.

We have minutes of the project in Word or pdf - sorry they are in Dutch.

The 2014 schematics were lost in time, so we needed to do some googling. The heart of the circuit is the 4060 binary counter:

The schematics is based on one from buildcircuit. However, we have 5 groups of LEDs, not three. And we added some capacitors for stabilization.

We will use the 4060 outputs to flash the LEDs; here are some time calculations.

We were initially puzzled by the diodes, we now believe they form a "wired OR", resetting the CD4060 when all three (five) transistor basis are high. This is when the CD4060 reaches 0b...111 (0b...11111). In that situation all LEDs are off.

In other words at the same moment all LEDs are switched off, the CD4060 is reset and outputs 0b...0000 and all LEDs are on.

Our final schematic.

I wanted the PCB to have small feet. I made a 3D model to check the positions and lengths of the slots.

A step that took quite some time was the design of the board outline. This includes the big "2022" digits, that I wanted to cut out. I made the design in Visio, because that can save to DXF, the format needed by the PCB tool.

The resulting PCB as a render, front and back side.

Find the whole design on oshwlab. The gerber is also available separately.

I ordered 5 red, 10 green and 5 black at JLCPCB; pricing: €1.76, €4.41, €3.53 respectively plus €15.85 shipping. Total €25.55.

The resulting PCBs are great looking.

Find below the cost of the boards and components. The LEDs, transistors, and resistors came from our stock, so I have added "guessed" prices. We might have ordered too few IC sockets and/or USB connectors.

There is an instruction leaflet for assembling the PCB: a doc or pdf version. Since the leaflet is for the children, it is in Dutch.

The assembled board looks like this (sorry, potmeter is on backorder).

For a video check YouTube.

The result (see video) looks ok, but we found some issues.

(end)