MiniRadio: Tiny Design, Big Sound

DIY MiniRadio Projects: Build a Pocket-Sized Player

Overview

A pocket-sized DIY MiniRadio is a compact, battery-powered FM/AM or internet-capable receiver you assemble from off-the-shelf components. Typical builds focus on portability, low power, and simple controls (tuning, volume, on/off). Common goals: learn basic electronics, create a retro-looking gadget, or add Bluetooth/MP3 playback.

Parts list (typical)

• Microcontroller / board: ESP32 (for internet/Bluetooth) or Arduino Nano (for FM/AM with tuner module)
• Radio tuner module: TEA5767 or Si4703 (FM) or RDA5807M (FM) / SI4844 (AM)
• Audio amplifier: PAM8302, MAX98357A (I2S) or small Class D amp
• Speaker: 0.5–2.5” full-range speaker (8Ω)
• Battery & charging:** 3.7V Li-ion cell + TP4056 charger module
• Controls & display: Rotary encoder or push buttons; optional OLED (0.96” SSD1306) or small LCD
• Enclosure & hardware: 3D-printed or repurposed tin, screws, switches
• Misc: PCB or perfboard, wires, resistors/capacitors, headers, antenna (wire ~20–30 cm)

Tools required

• Soldering iron, solder, flux
• Wire cutters/strippers, pliers
• Multimeter
• Hot glue or epoxy
• (Optional) 3D printer or Dremel for enclosure work

Two simple build approaches

1. Minimal FM analog radio (fast, low cost)

• Use RDA5807M module + Arduino Nano for simple button tuning.
• Amplify with PAM8302 and drive a small speaker.
• Power from a single Li-ion cell with TP4056 charging.
• No Wi‑Fi required; good for pure local FM listening.

2. Internet radio + Bluetooth (feature-rich)

• Use ESP32 for Wi‑Fi streaming + Bluetooth A2DP sink.
• Use MAX98357A or small amp for audio output; stream using libraries (e.g., Audio.h for ESP32-audioI2S).
• Add SSD1306 OLED for station info and rotary encoder for menu/tuning.
• Requires more code and setup but supports thousands of online stations and podcasts.

Basic assembly steps (ordered)

1. Mount tuner/microcontroller and amp on perfboard; plan wiring.
2. Wire power: battery → TP4056 → protection → device VIN; include power switch.
3. Connect tuner/microcontroller to amp output and speaker; add decoupling caps.
4. Add user controls (buttons/encoder) and display; wire ground/common.
5. Upload firmware: simple FM control sketch (I2C) for tuner or ESP32 streaming code.
6. Test functionality with multimeter and headphones before speaker.
7. Fit components into enclosure; secure with hot glue; route antenna.
8. Final test and calibration (tuning steps, volume limits).

Example code pointers

• RDA5807M Arduino libraries (for FM control)
• ESP32 HTTP stream examples and ESPAsyncWebServer for station presets
• MAX98357A I2S playback examples for MP3/streaming

Power & battery tips

• Use 3.7V Li-ion and a boost converter if you need 5V peripherals.
• Include a low-battery cutoff or monitor voltage with ADC to avoid over-discharge.
• Optimize for power: dim OLED, use sleep modes on microcontroller.

Enclosure and UX tips

• Place speaker at front with bass-reflex port if space allows.
• Use tactile buttons or a detented rotary encoder for better tuning feel.
• Label controls clearly; consider magnetic or USB-C charging access.

Safety notes

• Follow Li-ion battery safety: use protection circuits and proper charger.
• Ventilate enclosure when soldering components; avoid short circuits.

Further resources

• Search for “RDA5807M Arduino tutorial”, “ESP32 internet radio project”, and “MAX98357A I2S example” for step-by-step guides and code libraries.