See the "Toner Transfer" file in the "Schematic and Layout" section for a parts list.

The DY-SV17F is a low cost audio module available from many retailers including Universal Solder

The board has 4MB of flash for storing mp3 files, which must be named 00001.mp3 up to 00255.mp3 The leading zeros matter.

The board appears as a USB flash drive when connected to the computer with micro-USB.

The board WILL NOT PLAY SOUND when in flash drive mode. It MUST BE DISCONNECTED from the computer to work.

The circuit can be powered by a 5V USB charger connected to the board, or a 9V battery.

The 8 buttons are used to select sounds using binary... a good way to make students count in binary! Want sound number 23? Which buttons do you press? (Press and hold to play the entire sound.)

The MP3 board gives a 3W amplified speaker output and a classic audio signal on the DACL line. The case is designed for a 2.25" diameter speaker, but the board works with most common hobby speakers.

The audio signal is used to drive a 5V version of the Color Organ Triple Deluxe, originally posted by LEDArtist.

The circuit is a great way to teach RC filters and the differences between NPN and PNP transistors. For a video on this circuit see my Youtube page.

The values of the components are very forgiving... modest changes in most resistors or capacitors will simply affect the corner frequency of the relevant filter. The circuit will work just fine so long as the component values are relatively close. Any common NPN or PNP transistor should work fine as well, although the pinouts on this board are for the 3904 and 3906. Just make sure your Base, Emitter and Collector are in the correct holes if you use a different small signal transistor.

The test points are made using resistor leads. Bend them into a "U" shape with needle nosed pliers and solder them in place to give a convenient location to connect oscilloscope probes if you want to study (or troubleshoot!) the circuit.