Issue Triggering Tracks w/ MP3 Trigger

The end goal is building an animatronic Halloween decoration. Using the forum, I’ve been able to work through most of my stumbling blocks, but I have one issue I have just not been able to break through. In short, I’m having trouble getting the Mini Maestro to send the digital output signal to the MP3 Trigger to trigger the loaded audio track. I’ve detailed the troubleshooting steps I’ve taken below. Supporting images are included. I believe I am doing something wrong in the Maestro Control center. Any guidance would be appreciated.


  1. Pololu Mini Maestro 12-Channel USB Servo Controller (Assembled)

  2. Sparkfun MP3 Trigger

MP3 Trigger Troubleshooting -

  1. Track file labeled correctly.
  2. MP3 Trigger plays the loaded track manually.
  3. Tried relabeling, manually launching, and manually triggering Trigger 1,2,3 and 4 successfully.
  4. Row headers soldered on MP3 Trigger to make easier connections from Maestro to the MP3 trigger.
  5. Solder joints aren’t professional but confirmed working due to the MP3 Trigger playing the loaded track when trigger is manually jumped.
  6. MP3 Trigger has its own dedicated 12v 5amp power supply. (not shown in pictures)

Mini Maestro Troubleshooting -

  1. Servo outputs confirmed working by connecting and adjusting HS-805BB servos.
  2. Dedicated 6v 3amp power supply with blue jumper powering both the servo and board power.
  3. Trigger connection connected to output 0.
  4. Ground and trigger connections connected correctly.

Maestro Control Center Troubleshooting -

  1. Output 0 assigned Output function in the Channel Settings tab.
  2. No matter what target is set for Servo 0 in the Status tab, it does not set off the Trigger on the MP3 Trigger.

Other General Images

I do not see anything obviously wrong with your setup. Just to clarify, when you say you can trigger the tracks manually, do you mean by creating a short between the two pins on the MP3 trigger for the specified track, it plays (i.e. not using the on-board navigation switch)?

Could you try measuring the voltage output on channel 0 of your Maestro to make sure it is behaving as expected (i.e. 5V when the target is greater than or equal to 1500μs and 0V when it is below)?

Also, could you try disconnecting the wire from the Maestro’s channel 0 signal output and instead manually connecting it to a different ground connection on the Maestro to make sure that works?


Hi Brandon. I appreciate the help.

1.) Yes, when I create the short between the two pins on the MP3 trigger for the specific track, it plays.

2.) I’m not adept with the multimeter but I believe I measured it correctly. I’m showing 4.19V at 1500 or more. I’m measuring 11.9mv at 1499 or less.

3.) I disconnected the wire from Channel 0 signal output and manually connected it to the dedicated GND pin about the VIN pin on the other side of the board and the track played.

After further troubleshooting I found that Triggers 17 and 18 don’t go through the analog mux and will work properly with 3.3 to 5v as a “high”. I confirmed this by connecting everything up to Trigger 18, changing the value below 1500 causing the track to play on the MP3 trigger.

Triggers 1 through 16 need a pin mode change to Digital Input when not active, and a switch to Digital Output to drive low and activate which the Mini Maestro does not support.

Because of this I’ve decided to put more time into learning the scripting language required to complete my project.