I recently purchased a replica flux capacitor online with the intention of putting it in my car and using a USB port in the back to power it.
I was happy to learn that the plug it uses for the LED fading lights is a simple AC-DC one with ratings of

4.2V +/- 0.6V and 550mA

It has a handy 2 pin connector to go off to the LED strips so I feel all I need is a USB cable with a potentiometer in series with the positive side and I set it to a value where they light up.

However I'm a complete Electronic novice and racking my brain watching YouTube videos on the subject involving resisters in different combinations and there are a lot of potentiometers to choose from with different ratings.

If I could get some clarification that'd be great as I feel I'm oversimplifying the problem.

 

So you are telling us the LED strip you have Requires 4.2 V +/- 0.6 V or simply put 3.6 V to 4.8 V? If the car has a USB port that should mean you have 5.0 Volts available. You need just over 1/2 Amp as you mention 550 mA. You really only need to drop 0.2 Volts minimum. and at the high end you are looking at needing about a 5 Watt pot. If your USB port in the car can supply the current I would first try placing a simple 1N4002 diode in series with the LED string rather than a pot. That will drop about 0.7 Volts and give you about 4.3 Volts to the LED string, see how they look. The 1N4000 series have a forward current rating of about 1.0 Amp, close to twice what you need.

Ron

 

I doubt the LED strip needs it all as it has the ability to add more strips. The mains adapter is similar to a phone charger, those are the specs I gave.

The USB port in the car can supply 1A (if the rating is correct)

 

I doubt the LED strip needs it all. The mains adapter is similar to a phone charger, those are the specs I gave.

The USB port in the car can supply 1A (if the rating is correct)

Do you just want the pot to vary the LED intensity? Yeah, if you have 5 Volts 1 Amp available you can use a pot but looking at the power you will need about a 5 Watt Pot and about 10 Ohm and I would place maybe a 2 Ohm 5 Watt resistor in series with the pot so you can't exceed the 4.8 Volt maximum to the LED string.

Ron

 

Thank you so much for your help.

No I don't need them dimmable.

From what I can tell these pots introduce their own resistance? And to that end, what type?!

http://www.ebay.co.uk/itm/1-5-10-20...hash=item2a23c4d12c:m:mSeUFwhBM2w8PnYD2qmXXSA
Or these smaller ones.
http://www.ebay.co.uk/itm/1-100pcs-...hash=item3601e9edf0:m:mGPBxb2DapzZX2CCDbJWSRA

 

Thank you so much for your help.

No I don't need them dimmable.

From what I can tell these pots introduce their own resistance? And to that end, what type?!

http://www.ebay.co.uk/itm/1-5-10-20...hash=item2a23c4d12c:m:mSeUFwhBM2w8PnYD2qmXXSA
Or these smaller ones.
http://www.ebay.co.uk/itm/1-100pcs-...hash=item3601e9edf0:m:mGPBxb2DapzZX2CCDbJWSRA

If you don't need dimmable, the diode is a simpler solution.

 

From what I can tell these pots introduce their own resistance? And to that end, what type?!

A pot (potentiometer) is a resistor, a variable resistor. The pot has three terminals. You would join the center terminal to one of the end terminals and the pot would go in series with the LEDs. If you don't need a dimmable solution I would just try the diode as I mentioned.

Ron