Transformer requirement for LED lights

[mike31154]

Since the voltage vs current relationship for a diode or LED is nonlinear, the fact that your LED runs brighter with the 13.5 volt vs 12 volt supply makes sense. What doesn't make sense is that the "dimmer doesn't seem to have any effect". Not sure I'm fully understanding that part of your statement.

Depending on the load connected to a power supply, especially a smaller one loaded to near max, it will drop to a lower voltage level. That is, if you were to measure the voltage output of your 13.5 volt supply while it is under close to maximum load, I suspect you would read less than the rated 13.5 volts.

Here is a graphic of the voltage vs current curve of a LED or diode.



As you can see as the voltage nears the rated/maximum forward voltage of about 3 volts for the diode, the current rises sharply. This is why using a power supply of the correct voltage is so important, or you risk cooking your diode. However, something as simple as resistor in a circuit running a LED can keep the current at a safe level by dropping the voltage available to run the LED to its rated value. This is not efficient since the resistor wastes power & creates heat in doing so. This is why PWM (pulse width modulation) is commonly used to dim and control the current to LEDs, it is more efficient. That doesn't mean you can't also include components such as resistors and zener diodes in conjunction with PWM circuitry to help sense & control both voltage and current in designing your hardware. Often tradeoffs are made in efficiency vs simplicity of design in most of these components. This is why I was suggesting that it may be possible to use a 24 volt supply feeding your dimmer to safely run your 12 volt LEDs. Again, that may not be an experiment you wish to carry out. If I'm wrong, you could cook your lights.

[Aquacrazed]

I see, I think I will contact Fluval and ask them if a 24v power supply will work with this LED bar. I contacted Current USA, they say a 24v power supply will work for their LED strips.

[calo247]

you hit the nail on the head with the current graph, that is a pretty steep curve, do the strips use the Cree XR-E leds?

[calo247]

are these the strips you have?

http://current-usa.com/aquarium-led-...d-striplights/

if so it is really weird it came with a 13.5v supply when on their site it says it is powered by a 24v one, it even lists a part number for one.

you did mention before that the box said it could be hooked up to a 12v supply, was this a typo?

[Aquacrazed]

LED strips: http://current-usa.com/aquarium-led-...en-led-strips/
They don't come with a power supply, they say they can ben connected to a 12 - 24v

The 13.5v power supply came with the Fluval LED bar (it's the light that comes with the Fluval Evo 13.5 kit)

[calo247]

i cant see where it says it can be connected to a 24v supply, only talks about a 12v one, and supply in the parts list is a 12v one. maybe the person you talked to got confused on what strip you had maybe?

[mike31154]

Error, delete.

[Aquacrazed]

Originally Posted by calo247

i cant see where it says it can be connected to a 24v supply, only talks about a 12v one, and supply in the parts list is a 12v one. maybe the person you talked to got confused on what strip you had maybe?

I got a reply from Current USA:

The 24v transformer compatible with the Truelumen actinc strips can be found below:

https://www.amazon.com/TrueLumen-24-...nt+usa+24v+60w

[Aquacrazed]

Also just today I got a reply from Fluval:

We do not recommend you use a higher powered power supply as it will damage the unit and void your warranty.

[Aquacrazed]

I was looking on Amazon and noticed they have a used single ramp timer (https://www.amazon.ca/gp/product/B00...?ie=UTF8&psc=1) for $20. I decided to buy it and then use my Fluval LED bar though it and then use the dual ramp timer for my Current USA LED strips (actinics).

Thanks for all the help guys.