I am new to electrical engineering and I would like to build simple circuit with potentiometer as voltage regulator.

I have simple circuit, as you can see in attached picture below.


I have 12V/1000 mA DC source connected via potentiometer to LED strip (unfortunately I don't know the resistance of this component, strip is about 1.5m long - type 5050 if it will help somehow)

I would like to know what kind of POT should I use to regulate source to range 6 - 12V. At the moment I have chosen 1k Ohm POT and it dims LED strip only in first 10% of range then nothing happens at all because strip barelly shine.


1 Answer 1


What you are doing is not voltage regulation, but rather adjusting the resistance in series with the LEDs. This is a fine way to adjust brightness in principle - though it won't be linear, as you've observed - except for the fact that a potentiometer is not rated to carry the sort of current that flows through an LED strip. Potentiometers tend to be rated at 100mA or less, but 1.5 meters of LEDs will draw a lot more than that.

Your best option for controlling brightness fairly linearly is an adjustable constant-current supply - such as one like this:

enter image description here

An alternative that solves the power dissipation issue but not the linearity issue is to use a linear regulator like the LM317 with a potentiometer in the feedback loop - see that part's datasheet for an example.

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    \$\begingroup\$ BJT would be more adequate ;) although, the best is off-the-shelf led driver. \$\endgroup\$
    – user76844
    Jul 10, 2015 at 10:23
  • \$\begingroup\$ @GregoryKornblum A BJT on its own will have a high dependence on its beta, which doesn't make for a really reliable regulator. \$\endgroup\$ Jul 10, 2015 at 10:27
  • \$\begingroup\$ But you made a current sense resistor! The circuit will almost not depend on beta. On the other hand, the control circuit will be much more linear, while with MOSFET you will have hard time with stability and regulation. Trust me, i did this mistake once :) \$\endgroup\$
    – user76844
    Jul 10, 2015 at 10:30
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    \$\begingroup\$ @GregoryKornblum Oh, sorry, I thought you were suggesting using a BJT on its own as a current regulator, not replacing the FET with a BJT. I actually manufacture a series of dummy loads for hobbyists that use this exact circuit, and with a little compensation it's perfectly stable. \$\endgroup\$ Jul 10, 2015 at 10:55
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    \$\begingroup\$ @GregoryKornblum BTS117/BTS133/BTS141. They're rated for linear operation, and include various protections too. \$\endgroup\$ Jul 10, 2015 at 12:10

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