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A Monster LED Clock with Wi-Fi and Temperature Display

4-inch tall display, Internet time via ESP32, and remote sensors

A Monster LED Clock with Wi-Fi and Temperature Display
Those tiny boards with Wi-Fi-capable ESP32 controllers are a great starting point to realize all sorts of projects. That's what Rainer Krugmann thought when he came across some monster-sized seven-segment displays in his collection of electronic odds and ends. With the keen instincts of an engineer, he set about building a versatile clock which, thanks to a MQTT interface, also makes the design a versatile platform on which to build your own projects and extensions. A wireless sensor for air quality, temperature and humidity are already planned.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

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Download the BOM list
The BOM (Bill of Materials) is the technically exhaustive listing of parts and other hardware items used to produce the working and tested prototype of any Elektor Labs project. The BOM file contains deeper information than the Component List published for the same project in Elektor Magazine. If required the BOM gets updated directly by our lab engineers. As a reader, you can download the list here.
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Component list

Component List, display board


All SMD 0805, 0.25W

R1 = 1kΩ 10kΩ

R5-R11,R13-R19,R21-R27,R29-R35 = 43Ω *

R12,R20,R28,R36 = 680Ω *



C1 = 100µF, 25V, radial, 2.5mm lead pitch

C2 = 330nF, 50V, X7R 0805 *

C3,C6,C7 = 100nF, 50 V, X7R 0805*

C4,C5 = 1µF 50V, X7R 0805



D1 = MBR540

LD1-LD4 = SA40-19SRWA, Kingbright, e.g. Reichelt SA40-19RT *

IC1 = 7805, 5-V voltage regulator*

IC2 = ULN2803A, SOIC18-W

IC3 = MIC2981, SOIC18-W




ESP32 Pico Kit, Espressif [1]

PCB-mount power barrel socket, straight or right-angled. (Würth 694108402002 or 694108301002) *

2x20-way pinheader sockets for ESP32, SIL, 0.1“ pitch

K1 = 2-pin pinheader, 0.1“ pitch

K2 = 6-pin pinheader, SIL, 0.1“ pitch

K3,K4,K5,K11 = 4-pin pinheader, SIL, 0.1“ pitch

PCB # 180254-1 v1.2 (Elektor Store)


* = see text

Component List, sensor board


All through-hole, 0.25W

R1,R2 = 10kΩ

R2,R3,R4 = 1kΩ

R5,R6,R7 = 220Ω



C1 = 100nF, 50V, ceramic, radial, 5mm pitch



LED1,LED2,LED3 = red, 3mm diam.

D1 = BAT85

T1 = BS170

IC1 = TGS2600, Figaro



ESP32 Pico Kit, Espressif [1]

Sensor module DHT22, Air temperature and humidity *

Buz1 = piezo buzzer, e.g. PS1420P02CT, TDK

K1,K2 = 20-way pinheader socket strip for ESP32, SIL, 0.1“ pitch

K3= 3-pin pinheader, right-angled, 0.1“ pitch

S1 = pushbutton, SMD, e.g. S-TACTILE-6X6-PTH, Alps

PCB # 170182-1 v1.1 (Elektor Store)


* see text

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