24v DC to 12v DC converter for LED backlight

[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?

[Heckler]

the dc/dc converter you pointed to SHOULD work BUT may generate some(a lot??) of RFI. You may want to get one and test it.

I'm curious... why were you not satisfied with two LED strips in series?? Was it too dim? or too dificult to wire up that way?
From my perspecitive that really seems the very simplest way to solve your problem without the need for any more external components.

I would also breadboard up the circut and try the PWM via the ULN2003's and use the native 24vdc. (they can easily handle that voltage) If you keep the ON-duty cycle very short you should be ok.

Anyway... just trying to help you find the simplest solution.

[PJALM]

If I try connecting 2 LED strips in series the internal power supply just clicks and turns off and on. Maybe this whole time there was nothing wrong with the original backlights and was the internal power supplies at fault the whole time lol. Too late now, I allready converted them all to LED backlights.