I have 7 shelves that are 4 feet across that I want to light with LED strip lighting. After searching and looking for an answer, I can't find anything that is clear.

They are indoor shelves and need to be dimmable.

What kind of power supply should I use to power the LEDs? I am not sure what power supply I need to use when I have seven 48 inch strips running in parallel.

The LED strips I have are 20 inch individual strips and are cuttable every 2 inches, so I will make 48 inch strips out of these. Here is the LED strip specification from the website I bought them from:

enter image description here

Any help on this would be awesome. I don't want to buy the wrong power supply.


1 Answer 1


2.4 W per 20" = 0.12 W per inch.

7 shelves × 48" = 336"

336" × 0.12 W/inch = 40 W.

From P = VI we can calculate the required current = 40 / 12 = 3.3 A.

You need a 12 V, 4 or 5 A PSU with a 0 to 12 V voltage adjust capability. Usually for LEDs the dimming will be done by pulse-width modulation (PWM) which switches them fully on and fully off at a high enough frequency that the eye doesn't notice any flicker.

enter image description here

Figure 1. PWM signal transitioning from high pulse width (75%) to low (25%) and back again. Note amplitude remains constant. Image source and more reading on Dimmable mains power supplies.

  • \$\begingroup\$ Changing PS output voltage is not the way to dim led. PWM should be. It needs some special PS , which able to dim. \$\endgroup\$
    – user263983
    Commented Nov 21, 2020 at 16:09
  • \$\begingroup\$ thanks guys! just what i wanted to know. \$\endgroup\$
    – kris118
    Commented Nov 21, 2020 at 16:17
  • \$\begingroup\$ @user263983: Of course. I forgot to mention it. Corrected. \$\endgroup\$
    – Transistor
    Commented Nov 21, 2020 at 16:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.