Voltge / Current reduction question

[thenson]

I am in need of a way to attach a constant DC power source to a small cheap MP3 player (plugs into a phone system). I have all sorts of old DC power supplies around, but I need to get the voltage down to 1.5v for the MP3 player. Is there a simple circuit that I can put together to take a PS of, say, 4.8v / 350mA to the same voltage / current as a AAA battery?

Hope this make sense.

Thanks in advance... Todd

 

[audioguru]

You can use an LM317 with 2 resistors to set the voltage and 2 capacitors to keep it stable..The MP3 player draws as much current as it needs.

 

[prprog]

Mp3

thenson:

An MP3 player to attach to the phone? That is very interesting. Can you tell me which is that product/model ? Thanks.

 

[thenson]

Our system allows for music-on-hold by way of an external input. We've been using a CD player, but needed an updateable non-mechanical solution. Plugging the MP3 player in servers the purpose, but I need hard-wired power-- not a battery.

 

[thenson]

Educate me...

You can use an LM317 with 2 resistors to set the voltage and 2 capacitors to keep it stable..The MP3 player draws as much current as it needs.

Point me in the right direction... or show me the circuit. I'm new to all this.

Thanks... Todd

______
"Don't tell me I can't do something!"

 

[audioguru]

The LM317 is the most popular adjustable voltage regulator. The datasheet shows you how to connect it and has a calculation for its resistors for it to produce any voltage you want.
Its minimum input voltage must be 2.5V higher than its output voltage.
If it gets hot then it needs a heatsink.
Here is a circuit with it providing 1.5V: