24v DC to 12v DC converter for LED backlight

[Heckler]

LED's are a current driven (dependant) device. In other words don't be concerned about the voltage... pay attention to the current.
Do your LED strips include current limiting resistors? If so you should be able to include an external resistor to further limit the current and still be able to use the existing 24V supply.

Another thought would be to series two of the LED strips together and therefore make a 24V LED strip.

You can drive the same LED with 3, 12, 51 or 120 Volts by just changing the current limit resistor to a value that allows only the proper current to flow.
If you google "LED resistor calculator", or some similar phrase, you will find numerous examples of how to calculate the risistor value for a given LED and voltage.

hope this helps

[PJALM]

Thanks for the help. The LED strips are the waterproof type unfortunately so I can't change the resistors on them. Every 3 LEDs has a resistor and each strip has 66 LEDs. I did try to use 2 strips in series but didn't work so well.


Here is an Idea I am working with so far, let me know if this looks feasible or not. I am not all that sure about the VRs, can you use multiple in parallel to achieve higher amperage?

Thanks.

[PJALM]

The LED strips are arranged as follows and are fixed so I can't change them. They come on a 5M reel and have 12v rated current limiting resistors.

[Heckler]

I did try to use 2 strips in series but didn't work so well.

Why did that not work?? It seems like it should have. You also should be able to supply an external Power resistor to drop half the supply voltage (which would be wasted as heat, not so good).

One thing you might consider would be to drive the ULN2003's using a PWM (pulse width modulated) signal at 50% duty cycle (or less for less brightness) and still use the native 24V supply.

Using the LMxxx regulators you are also going to be wasting half the consumed power as heat, dropping the 24v to 12v. A switching regulator (something I'm not vary familiar with) is the more efficient way to go.

Again, I would go back and find out why the parallel LED strips arent working. You would probably need to make sure each of the LED strips have the same number of LED's in each strip. Then just feed into one strip, cross over to the second strip and then to ground.

PS what is your source of LED strips?? I have been looking for some for a project.

[PJALM]

These are the LED strips I used. I wanted the Non-Waterproof but mis-ordered

[Heckler]

Again, I would go back and find out why the parallel LED strips arent working

Oops, I should have said "series LED strips".

I checked your link to the Ebay LED strips... then clicked on over to their store. I may try the RGB led strips. Thanks!!

and good luck with your project.

[PJALM]

Would THIS work for what I want?