How to make a 5v supply

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Use 7805 chip.
 

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Is 14V the spec voltage, or measured voltage? Measured is often times higher than what is specified.

So if measured voltage is 14, then you are dropping 14-5=9v.
For a linear regulator (such as the 7805), it will have to dissipate 9v times current draw of the bluetooth module. Depending on what the current draw is, the total power may require some heatsinking of the linear reg.

There are newer technology, lower noise versions of 7805's out there, depending how much you want to spend, and how good you want this to be.

7805 is cheap and easy, and will probably handle the power, so its something you can try and see how it works/sounds.
 
You can buy a LM317 regulator module from e-bay - should already include a small heatsink. Cost is usually peanuts.

Put a "test load" resistor of say 200 ohms on the output and adjust the voltage output to the 5v you need for your Bluetooth module, then attach the bluetooth module instead of your test load resistor and you are good to go. The LM317 regulator should have better specs than most 7805's as well.
 
Or get a cheap cigarette lighter socket 12 V to USB SMPS converter and use it's PCB.
Best regards!

Simple, very, very cheap, veryvcompact, robust and reliable idea - I like it!

(in-car nom '12v supply' is all over the place, usu 14.2-14.4v when running, right in the target area and these adaptors are designed for both this, and to withstand much higher spike from bus transients/alternator load dumps. This is a neat idea.)
 
And a good way to inject HF noise to the 14v DC rail as well. If I wanted to go that way, I personally would use a wall wart better, at least most of the switching noise would remain at the other side of the existing trafo.

Fortunately there are AC/DC small linear power supplies for very little more money. That's what I would use, If I though that noise in the 14V rail could compromise the sound quality.

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cebek 5v power supply - Google Search

Regards.
 
You can buy a LM317 regulator module from e-bay - should already include a small heatsink. Cost is usually peanuts.

Put a "test load" resistor of say 200 ohms on the output and adjust the voltage output to the 5v you need for your Bluetooth module, then attach the bluetooth module instead of your test load resistor and you are good to go. The LM317 regulator should have better specs than most 7805's as well.

+1 for the cheap and venerable LM317
 
Hi I would like to add a Bluetooth module to my amp my amp currently runs of a 14v DC supply. I would like to make a 5v rail to run it but have no idea how to achieve this any input is welcome thanks.

If you're going to put the BT receiver in the amp case then I'd say it's going to have a pretty poor range, and if you're going to have an external receiver than you might as well power it separately too, which will circumvent the noise problem that you are inviting.
 
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