Comimark 2 Pcs Mp3 Lossless Decoders Decoding Power Amplifier Mp3 Player Audio Module Mp3 Decoder Board Support TF Card USB

I didn't have any problem with these... soldered some leads onto the BAT + and - pads, hook it up to a 5VDC power supply, and they run fine and play mp3 files as described.

The Comimark MP3 player board is very useful for playing alert tones from a 5v power source. Unfortunately, there are no instructions to speak of other than that in the product description.As the package contains two, I experimented with one to find out its voltage limits and damaged it, but that's ok, and not the fault of the unit.The MP3 board runs off of 3.7-5.5vdc ONLY. This can be provided through the microUSB connector or by the BAT+ and BAT- terminal holes on the board. The microUSB connector does not appear to support data communication.The speaker should be connected to the Terminal Block marked "SP+" and "SP-" The amplifier is Mono and has adequate power to drive a very small speaker. Maxing out the volume causes distortion when using a 40mm 4ohm speaker, but this is OK for an alert tone. Fortunately, the volume setting is retained after power off. I suspect this amplifier would be happier with a small 8ohm speaker.There is an unmarked 3.5mm headphone jack. If you connect a speaker to it, it plays at a much lower volume than the speaker terminals. I suspect that it is a preamp out port, meant for use with an external amplifier. This port does respond to the Volume control buttons as do the speaker terminals.I used only a 16gb SD card during testing and did not test the USB A port. This port is intended to utilize a USB thumb drive.Increasing the input voltage to 7.5v caused a shutdown and subsequent short circuit on the power input, as well as a burning smell. Surprisingly, the test unit worked again after shutting off. They mean it when they say the voltage range is 3.7 - 5.5v! Also, do not attach the power leads to the speaker terminal block labeled only with "SP+" and "SP-"... This would likely damage the amplifier.In summary:If you have a device that can provide 5v, such as a robotics project or a 3D printer, and you wish to add an audible alert when a 5v output is activated, this Comimark MP3 player board is a nearly ideal solution. It can drive a small speaker directly or output to a larger amplifier with its 3.5mm port. A single MP3 file will play automatically and continuously as long as power is applied.

Junk, neither worked at all. I have other similar boards that work fine using the same power, speaker and sound file. There were dead on arrival. I regret that I didn't get around to returning them for refund soon enough....

Yes another DIY project that takes having the micro USB or USB plugged into a port to wake it up. This is so stupid. Will work with 3.7 battery but you cant use it on the go.. Would love to see a stripped down PCB board with just a micro USB with out the giant USB port (thumb drive). Don't know why you need both, just taking up extra space... Wouldn't say this is a stream lined setup at all, foot print is fairly big.. Can find a cheaper setup with just the headphone port, with more buttons and blue tooth. But still has the giant USB thumb drive port?..