Autostart DFPlayer Mini Without a Microcontroller

August 28, 2025 / 0 Comments

When I build battery-powered sound effects, I typically use the DFPlayer Mini. It is a tiny MP3 player that plays tracks from a microSD card and includes an amplifier for small speakers.

Typical application circuit without a microcontroller (arduino / raspberry pi pico) is ADKEY or IO mode. Wire up a push button to the right pin, and music plays when you push a button.
https://wiki.dfrobot.com/dfplayer_mini_sku_dfr0299

But what about autoplay, no button?

To make music start as soon power is applied, you can make use of a less documented feature of ADKEY1. If you hardwire wire GND to ADKEY1 (no pushbutton): Track 1 will start playing when power is applied and then loop.

  • Genuine modules bought from dfrobot.com have this feature.
  • Every clone variant I tried would not auto play when wired like this. Instead requiring a button press a short time after power up.

If you are purchasing dfplayer mini from any source that is not dfrobot or an authorized reseller, assume that you are purchasing a clone? octopart.com has a list of authorized resellers.

DFPlayer Mini Clone Auto Start Circuit

The circuit below is a slight tweak on : https://gabunz.wordpress.com/2021/04/24/autostart-autoplay-am-dfplayer-mini-ohne-arduino-mikrocontroller/ (German)

The idea is to use a small RC delay that drives an NPN transistor, so the ADKEY1 pin sees a short high pulse during power up, then is held low so the sound effect loops.

Theory: For a short period after power is applied, the capacitor is charging and the transistor is off. Eventually the capacitor voltage rises high enough that the transistor turns on. The time constant of 560kohm and 4.7uF is 2.6 seconds.

When power is disconnected, the capacitor slowly bleeds down through the NPN’s BE junction. This takes about 25 seconds. We can speed this up by using a DPDT switch, so the circuit is instantly re-triggerable.

  • Switch Common1 to V+ Battery and NormallyOpen1 to DFPlayer VCC.
  • Switch Common2 to Ground and NormallyClosed2 to NPN base.

The time constant of 22kohm and 4.7uF is 0.1 seconds.