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Display

The display (Displaymodul) is the device's only visual output: a single 20 mm 7-segment digit that shows the current player number, countdowns, and game state. It also carries the piezo buzzer for game sounds. Both are driven from just four Arduino pins, because the segments go through a shift register.

Circuit

A single 74HC595 shift register (SMD) drives the display. The Arduino clocks 8 bits into the register serially; the register's eight outputs drive the seven segments plus the decimal point, each through its own 330 Ω current-limiting resistor (8× 330 Ω total). This trades three fast MCU pins for eight segment lines.

The 7-segment digit is common cathode (part SC08-11). The buzzer (EKULIT AL-60P12) is driven directly from a dedicated MCU pin.

Displaymodul PCB, top side
Displaymodul PCB — top
Displaymodul PCB, bottom side
Displaymodul PCB — bottom

Board markings

Marking What it is
Summer The piezo buzzer (Summer is German for buzzer). The + marks its positive pin.
U1 The 74HC595 shift register, an SOIC-16 SMD part on the bottom side. The dot and the notch in its outline mark pin 1.
R1–R8 The eight 330 Ω series resistors, one per shift-register output: seven segments plus the decimal point. SMD, bottom side.
Display The 6-pin connector to the control board. Pinout in the table below.

Parts & datasheets

The components populated on the board, with the datasheet for each part archived in the repo where available. The eight segment resistors are the same 330 Ω SMD 1206 part used elsewhere — see the note on the BOM page.

Component Qty Part / supplier Datasheet
7-segment 20 mm digit (common cathode) 1 SC08-11 PDF
74HC595 shift register (SOIC-16, SMD) 1 SMD HC 595 PDF
330 Ω resistor (SMD 1206) 8 Reichelt SMD 1206, segment resistors PDF
Piezo buzzer 1 EKULIT AL-60P12 PDF

Photos of the board, before and after assembly. Click any of them for a larger view.

The bare Displaymodul PCBs: the top with the buzzer and 7-segment digit footprints, the bottom with the 74HC595 and the eight segment-resistor pads. Assembled Displaymodul, top side: the 7-segment digit and the piezo buzzer. Assembled Displaymodul, bottom side: the 74HC595 and the eight 330 Ω resistors. Assembled Displaymodul edge on, with the 6-pin header and the display's part label. Three assembled Displaymodul boards: the 7-segment digit, the piezo buzzer, and the 6-pin header.

Fritzing source: Displaymodul.fzz.

Connector (6-pin)

The module connects to the control board through a 6-pin header. The three shift-register control lines and the buzzer map to Arduino digital pins as shown. The module runs at 5 V:

Pin Signal 74HC595 role MCU pin
1 Vcc +5 V —
2 GND —
3 DS serial data in D8
4 STCP storage-register clock (latch) D9
5 SHCP shift-register clock D10
6 Buzzer piezo buzzer drive D11

To update the digit, the firmware shifts 8 bits out on DS/SHCP (D8/D10), then pulses STCP (D9) to latch them to the outputs. For the complete signal map across all modules, see the wiring.