How to Build a Tiny Low-Power Voice Recorder with Common Parts

Introduction

Building your own low-power voice recorder from common electronic parts is a fun and educational project. With just a few inexpensive components, you can assemble a device that will let you capture audio in a compact package.

In this guide, I will walk you through step-by-step instructions on how to build a simple yet functional voice recorder using commonly available parts. We will cover:

What You Will Need

• Microcontroller (e.g. Arduino Nano)
• Microphone and amplifier module
• Micro SD card module
• Battery pack (e.g. 3 x AAA)
• Enclosure (e.g. Altoids tin)
• Basic electronic components

How It Works

• The microphone picks up audio signals which get amplified by the amplifier module.
• The microcontroller converts the analog signal to digital and stores it on the Micro SD card as an audio file.
• Power is supplied by the battery pack. All the components fit inside a small enclosure.

Benefits

• Very compact and portable
• Low cost to build
• Good audio quality
• Fun DIY electronics project

Let's get started!

Step 1: Gather the Required Electronic Components

To build the voice recorder, you will need the following main components:

• Microcontroller board - This acts as the brain of the device. An Arduino Nano or any similar small microcontroller will work well.

• Microphone and amplifier module - This picks up the audio input and amplifies the signal. Many inexpensive modules are available that combine a microphone and amplifier on a small PCB.

• Micro SD card module - This allows the microcontroller to record data onto a removable memory card. Get one that is designed for Arduino.

• Battery holder and batteries - To power the device untethered, you need a holder for AAA batteries and the batteries themselves. A 3x AAA holder is a good compact choice.

• Enclosure - To house all the components together, you need some kind of enclosure. A recycled Altoids tin is ideal.

• Assorted electronic components - Resistors, capacitors, jumper wires and so on to wire up the circuit.

For the best experience, I recommend getting a beginner electronics component kit that includes all the above items. That way you will have all the necessary parts in one purchase.

Step 2: Prepare the Enclosure

The enclosure I chose for this build is an Altoids small mint tin. This provides a compact, rugged and low cost housing for the voice recorder circuit.

To prepare the enclosure, follow these steps:

• Open up the lid and use a flat file to file away any remnants of the mints tray that are still attached. You want to clear space for the components.

• Using a hobby knife, cut a rectangular opening on one side of the enclosure for the Micro SD card slot to fit through. Make the cutout just large enough to fit the Micro SD module.

• Drill two small holes on the opposite side for the microphone and amplifier to mount in. The holes should align with the mounting holes on the microphone board.

• Clean the enclosure thoroughly to get rid of any dust, oil or particles left over from the mints.

The enclosure is now ready to install the electronics in.

Step 3: Connect the Microcontroller and Micro SD Card Module

The first components to wire up are the Arduino Nano and the Micro SD card module.

Follow these steps:

• Insert the headers provided with the Micro SD module into the breadboard holes on the module.

• Connect the MISO, MOSI, SCK, CS and GND pins on the module to the matching pins on the Arduino using jumper wires.

• Power the Arduino by connecting the 5V and GND pins to the breadboard rails.

• Insert a formatted Micro SD card into the slot on the module.

• Load a Micro SD card recording sketch onto the Arduino IDE and upload it to the Arduino Nano.

• Connect the Arduino to your computer via USB and open the serial monitor. It should now be able to log data to the SD card.

The essential digital voice recording components are now connected!

Step 4: Add the Microphone and Amplifier

Now we need to add the analog audio input circuit using a microphone and amplifier module:

• Solder headers to the pins on the microphone board so it can plug into the breadboard.

• Connect the audio out pin on the module to the analog A0 pin on the Arduino using a jumper wire. This feeds the amplified signal to the analog input of the Arduino.

• Connect the VCC and GND on the module to the breadboard rails.

• Mount the microphone board into one of the drilled holes in the enclosure using hot glue to hold it in place.

• Load an Arduino sketch for analog audio recording and sampling.

• Make some test recordings by speaking into the mic while powered via USB. Play back the recordings to verify quality.

At this point your device should be able to record voices clearly!

Step 5: Power it with a Battery Pack

To make the voice recorder fully portable, we need to power it with batteries instead of USB:

• Connect the positive and negative wires from a 3x AAA battery pack to the breadboard rails.

• Load batteries into the battery pack holder.

• Verify it powers on the Arduino and microphone module as expected.

• To conserve battery, add code to the Arduino to turn off components between recordings.

• Solder or tightly twist wires from the battery pack to the rails for a secure connection.

• Hot glue the battery pack into the base of the Altoids tin enclosure.

Now your voice recorder can run untethered!

Step 6: Final Assembly and Usage

We're in the home stretch! Follow these final steps to complete the build:

• Neatly arrange all the components in the enclosure and secure with tape or hot glue as needed.

• Slot the Micro SD module into the cutout in the side of the enclosure.

• Cut sections of foam padding to protect the components from shaking.

• Close up the enclosure and secure the lid.

To use your new voice recorder:

• Turn it on using the battery pack switch.

• Make recordings by speaking into the microphone.

• Play back recordings by removing the SD card and putting it in your computer.

• When finished, turn it off to conserve battery life.

And that's it! You now have a tiny, battery-powered voice recorder you can build for under $30. Enjoy putting it to use for memos, lectures, music and more!

Summary

In this guide, I covered the full process of assembling a miniature voice recorder using simple electronic components:

• The key parts needed include a microcontroller, microphone module, Micro SD module, battery pack and enclosure.

• Wiring up the modules to the Arduino provides digital and analog audio recording capabilities.

• Powering the build with batteries makes it completely portable.

• A small tin provides a rugged enclosure that fits in your pocket.

Building your own electronics like this voice recorder is tremendously fun and educational. I hope you're able to use this guide to create your own compact audio recording device. Happy building!