1000 mah ldd drivers too much?

[coralbeauties]

I have a frag tank and a display tank which both have the same diy lights other then the drivers. The display has an ardurino system with 1000 mah ldd drivers and my corals dont have as good p/e as my corals in the frag tank that the light is driven off the standard 700 meanwell driver. I am beginning to wonder if the 1000 drivers are too much. colors are fine in both tanks and they do share the same water. Before I go and order $60 worth of new 700 ldd drivers I thought I would throw this out here for any opinions.
thanks
Jeff

 

[twilliard]

I would think that would be the same as dimming the led chips from 1000ma to 700ma
Are you running the DT at 100%?

 

[coralbeauties]

From what I was told on another thread, the leds will be driven at 1000ma but just cycled on and off more often to attain the dimming effect. So if I am understanding it right the corals would be getting the punch of the 1000ma drivers but for not as long. with full power being at 255 I believe that I have them set at 175.
thanks
jeff

 

[twilliard]

The dimming drivers regulate current

 

[TheEngineer]

The LDD drivers are constant current so they will, ideally, always put out 1000mA of current when on. I would need to look clos r to see what the actual output of these are when being controlled. That said, they probably are modulated by a duty cycle output. (Aka they blink on and off)

There's really little difference, in my opinion, between running them with a reduced duty cycle and running them at lower current. You need to think about a longer time period than each blink. The brightness we see is an integration of all of the photons hitting our eyes. The chlorophyll in the corals works the same way. The lower the duty cycle, the less photons produced.

 

[TheEngineer]

Just looked it up, they do operate on a duty cycle to dim.

 

[coralbeauties]

Tks for all the replies. I am assuming in my dummy terms then that dimming the 1000ma would be the same as running the 700s full strength.?
Tks
Jeff

 

[twilliard]

Running the 700 at 100% will only be 700ma compared to the 1000ma

 

[theatrus]

There is one thing that's missing here: a 70% 1000mA driver and a 100% 700mA driver will have the same energy delivered ( not actually true but bear with me for a moment), but the 100% 700mA setup will actually put out more PAR. Why? LED efficiency is not linear with drive current, and a 700mA driven LED is more efficient, even if it's on 100% of the time.

A LEDs Vf (forward voltage, the voltage drop) also scales with the drive current, usually linearly in the area we are concerned about. It increases as current increases. More Vf means more power from the driver, even if current remains the same.

So not only do you get lower PAR, you're also using more energy to do so.

How much? We need to look at the charts on the LED data sheets. It could be a noticeable difference.

For example, here is the Luxeon T:

At 1000mA it will deliver only ~1.3(2?)x the light than at 700mA, for 1.35x the current. Not too great of a difference, but still around 3-4%. If the increase in current were to change the Tj (junction temperature) the difference would be bigger.