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What This Project Is
This project builds a digital hourglass using an Arduino Nano R4, two 8x8 MAX7219 LED matrices, and an ADXL335 accelerometer. When you flip the 3D-printed hourglass, virtual sand grains flow from one matrix to the other, simulating real physics. It’s a neat desk gadget and a solid introduction to combining microcontrollers, LED matrices, and sensor input.
The original Arduino Project Hub page provides the code and 3D print files, but some of the component links are generic or point to older versions of parts. This companion page offers a verified bill of materials with current buy links, clarifies critical power supply considerations, and includes practical build tips gathered from the community.
What You’ll Need to Buy
| # | Component | Spec | Qty | Buy Link | Notes |
|---|---|---|---|---|---|
| 1 | Arduino Nano R4 | Renesas RA4M1 Arm Cortex-M4 48 MHz, 5V operating voltage | 1 | Arduino Official Store — Nano R4 | The original project used an older Nano, but the R4 is used in the redesign. DO NOT use a 3.3V logic Nano variant. |
| 2 | ADXL335 Triple-Axis Accelerometer Breakout | ±3g analog output | 1 | Adafruit — ADXL335 Breakout | CRITICAL VOLTAGE NOTE: The Adafruit version has an onboard regulator and accepts 5V. If you buy a SparkFun SEN-09269, it requires 1.8-3.6V and must be powered from the Nano R4’s 3.3V pin. |
| 3 | MAX7219 8×8 LED Matrix Module | MAX7219 driver IC, 8×8 common-cathode LED matrix, 5V VCC, SPI | 2 | Amazon — MAX7219 Module | Any standard 5V MAX7219 8x8 module works. These are daisy-chained. |
| 4 | 3.7V 18650 Lithium-Ion Battery | 3.7V nominal, 18650 cell format, min 1000 mAh | 1 | Amazon — 18650 Battery | Any protected 18650 cell works. You’ll need a TP4056 module to charge it safely. |
| 5 | TP4056 Lithium Battery Charger Module with Protection | 5V/1A input via USB, 4.2V charge cutoff, over-discharge/over-current protection | 1 | Amazon — TP4056 Module | Get the variant with built-in protection (dual-function board), not just the bare charger. |
| 6 | 5V USB Boost Converter / Power Module | Input 3.0–4.2V (Li-ion), output 5V, min 500 mA | 1 | Amazon — 5V Boost Converter | REQUIRED: The Nano R4 needs 5V on USB-C or 6-21V on VIN. A raw 3.7V Li-ion cell is too low. This boosts the battery voltage to 5V. |
| 7 | Jumper Wires / Dupont Cables | Male-to-female and male-to-male, 10–20 cm, 2.54 mm pitch | 1 pack | Amazon — Jumper Wires | Standard breadboard jumper wire set. |
| 8 | Soldering Iron and Solder | Temperature-controlled station recommended; 60/40 or lead-free solder | 1 set | Amazon — Soldering Station | Essential for connecting components permanently. |
Estimated total cost for components: $40-65
You will also need a 3D printer (FDM) to print the enclosure.
Where to Get the Files
- STL Files (Enclosure): https://github.com/EDISON-SCIENCE-CORNER/LED-HOUR-GLASS
- Firmware: https://github.com/fbrnc/Arduino_Hourglass
- Wiring Diagram: https://github.com/EDISON-SCIENCE-CORNER/LED-HOUR-GLASS/blob/main/CIRCUIT.png
- Bottom STL: https://github.com/EDISON-SCIENCE-CORNER/LED-HOUR-GLASS/blob/main/BOTTOM.stl
- Top STL: https://github.com/EDISON-SCIENCE-CORNER/LED-HOUR-GLASS/blob/main/TOP.stl
- Fritzing File: https://github.com/EDISON-SCIENCE-CORNER/LED-HOUR-GLASS/blob/main/hourglassfzz.fzz
Build Notes
- Library Installation: The most common hurdle is getting the libraries installed correctly. After extracting the project archive, navigate to
hourglass-main > src. All necessary dependent libraries are located there. Copy these folders into your Arduinolibrariesdirectory (usuallyDocuments > Arduino > libraries). - Power Supply Path: The Arduino Nano R4 requires 5V via its USB-C port or 6-21V on its VIN pin. A raw 3.7V Li-ion battery cannot directly power it. You must use a boost converter (like the one listed) between the TP4056 module’s output and the Nano R4’s power input (either USB-C or VIN, depending on your boost converter’s output).
- ADXL335 Voltage: Be careful with the ADXL335 accelerometer. If you buy a SparkFun SEN-09269 (without an onboard regulator), it needs 1.8-3.6V VCC. Power it from the Nano R4’s 3.3V pin, not the 5V rail, to avoid damaging it. The Adafruit version (#163) includes a regulator and can safely take 5V.
- 3D Printing: MAX7219 LED matrix modules are surprisingly bright. They can shine through 3D-printed PLA, so you don’t need to cut apertures in the hourglass case for the displays. Print the case solid for a cleaner look.
About This Page
Some Assembly Mandatory builds supply guides for popular maker projects. We research and verify every component link so you can focus on building, not shopping. This guide was researched and compiled with AI assistance and reviewed by our editorial team. Found a dead link or a better component? Let us know.