If you use a 1.5v or a 3v battery powered MP3 player for long periods of time, you may get tired of constantly changing batteries. Some older players do not work will NiMH rechargeable batteries so changing out batteries can get expensive. The circuit below can be wired into the player, to replace of one or two AAA or AAA batteries designed by using a very common LM317 adjustable voltage regulator.
The circuit uses any off-the-shelf +5v to +6v power adapter. These are often used for USB powered devices and can be purchased from a variety of sources. I included an illustration showing how to make a simulated AA or AAA cell, using a wood dowel and metal electrodes from an old battery. You solder wires onto the electrodes then glue them onto the ends of the wood dowel, cut to the right length. The dowels can then be snapped into the player’s battery holder with the two wires routed to the eliminator circuit.
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