A compact USB powered audio player module with up 32GB capacity using removable Micro SD cards. Quickly update audio content using drag and drop interface, since the module acts like an external USB drive when connected to a computer. Available in two different models, photoresistor or button switch, to control audio play.  This project was inspired by the need to create a device to help my daughters wash their hands for at least 20 seconds, to help fight COVID-19. The idea was, they would wave their hand over the sensor (photoresistor model), triggering a random 20 sec audio clip. Once the song stopped, they could then rinse and dry their hands, and be sure their hands were clean. I initially created a playlist, cropping songs down to the 20 sec time limit using Audacity, but later decided to add a fade function, eliminating that step, and saving all that work. As time passed, I decided to add more and more features, so that this design could replace other audio circuits using the WTV020SD or WTV588d modules used in prior projects, ie. Easy Button hacked to play audio clips from "Office Space", delayed sounds of Moaning Myrtle when entering a restroom after turning on the lights, continuously playing random Halloween and later Christmas songs when a room light is turned on, etc. The afore mentioned voice/IC modules from Waytronic are far superior when it comes to power consumption, with a standby current down to 10uA, making these ideal for battery power. Unfortunately, these have limited storage capacities with the WTV588d (4 MB flash) and WTV020SD (1 GB Micro SD), and require converting the MP3 files to WAV or AD4 format. They do have a model, WT2000B02, with up to 32GB storage, but 8 times more expensive. The DFPlayer Mini module offers an inexpensive solution, using user supplied Micro SD cards for storage (without the 1GB limitation of the WTV020SD module), and uses standard MP3 file format, making it easier to use for people not versed in the various methods of converting files to non-standard AD4 files. Where this module is lacking though, is power consumption, thus the reason to rely on USB instead of batteries to run. Because some use cases require a switch to trigger the audio, that option was also included. So the USB Micro SD Player operates using a momentary push button switch or photoresistor (used for hands free applications). Only one or the other is installed, since the switch conflicts with the operation of the light sensor. It was initially designed to be compact enough to fit inside a small Altoids tin, to keep it as inconspicuous as possible. It's small size should make it easy to fit in tight places. The USB, speaker, photoresistor or switch, and LED all have external pins to allow these devices to located elsewhere, and still be attached to the circuit. **Features:** - Multiple play modes (full song, 20 sec, book, auto play). - Adjustable volume settings (low, med, high). - Intervalometer to control how often and how many songs are played. - Play mode and settings retained through power cycles. - Plays your MP3 and WAV audio files stored on Micro SD card. - Emulates USB drive when connected to computer for easy file transfer. - Hands free or button switch audio control, depending on model. - Status LED for indicating play mode, settings and module status. - Use in DIY projects needing compact audio player with up to 500+ hours of content. - Powered by USB phone charger. **Specifications:** - Power Requirements: 3.2V - 5.0V - Standby Current: 23mA - Speaker: 3W / 4 or 8ohm - Storage: Micro SD card (32GB max) - Audio Files: 128 (max) - File Format: MP3, WAV - Control: Photoresistor or Button Switch - Audio Module: DFPlayer Mini - Microcontroller: ATTINY85 - Size: 3.5 x 3.0cm / 1.38 x 1.18in [https://github.com/yeri63-arduino/USB-Micro-SD-Player-Module](https://github.com/yeri63-arduino/USB-Micro-SD-Player-Module)