hi ya all

i want to put my mp3 player in my car and supply it a constant voltage of 1.5v (it consumes very small amount of ampere).

how can i build a circuit that will give me a voltage of 1.5 DC out of the car's battery 12v (the actual voltage is between 12-13.8) DC?

tnx and good day

 

Here's one way:
http://www.circuit-innovations.co.uk/LM317.html
R1=47 and R2=220

 

Whatever circuit you decid to use, be sure to use a fuse!

 

National Semiconductor / Fairchild do an SOT-23 sized 1.5 volt LDO and they are pretty cheap. Your MP3 should run fine off 1.2v so use two diodes and a resistor for a really simple regulator.

 

As Ferez has indicated it s consumption is LOW, the best thing is to leave it on its battery and make best use of its portability, rather thanrisking all these trials.

If ore power is needed better to adopt a D cell by external implementation and it will be stomach full for a month , i suppose.

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Regards,
Sarma.

 

That will result in 7.1V, and probably smoke from the MP3 player. You have reversed the values. The desired values are R1=220, R2=47.

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Ron

 

Most senseable answer yet. A decent NiMH will run for hours and not damage your MP3 player.

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Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com/

 

hi guys, first of all i want to thank ya'all for the answers.
second thing, the MP3 player can't be feed through a regular battery because it will be molded\glued to my dashboard (i need to make it look like a built-in gadget in the dash).

so, what is the best solution? the LM317?

 

A remote battery holder.

A simple power supply may not provide isolation from electrical noise etc.

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com/

 

Use a rechargeable battery and charge it with the 12v output of the car

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adopt a cellphone charger with 5v output from the car battery- then use aa LM317 adj pin grounded and you will get 1.2v volts output. mostly, this is sufficient for the mp3 player.

first make dummy load trial outside and then use it for the regular device.

__________________
Regards,
Sarma.

 

OOPS!!! Sorry if I caused any damage

 

sorry for the stupid question but, how do i make a dummy load? what is the dummy load consists of?

 

You still need a resistor on the output as it has a minimum load requirement of 10mA so it won't regulate properly if you MP3 player uses less than that.

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I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

HERO999 is very much correct for the minimum load requirement.
Try putting one red LED with a series resistor of say 82 to 100 ohms and connect across the common ground and +3.3V output. this will work as artificial load (so called dummy load) . Artificial load could also be a 150 resistor but you won't know unless you measure. In the other case, the LED glows. how ever you can calculete the resistor value to suite 70% of maximum permitted current for the RED LED.generally Red LED drops 1.4V across it in the forward direction thus series resistor would be (3.3-1.4)/permitted current for the LED.

__________________
Regards,
Sarma.