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vbsaltydog
03/22/2010, 01:09 PM
My T5 2 x 24w ballast for my aquamedic oceanlight just burned out and the cost to replace it is ~50.00 so I was thinking of DIY two LED strips to put in the place of the T5s.

Reasons are:

(1) less bulb/ballast replacement
(2) ability to ramp the bulbs up/down for advanced sunrise/sunset effect.

Questions are:

How many Cree XR-E LEDs would you put in each 24" strip to provide actinic supplement to a single 250w MH provided there are going to be 2 LED strips?

If this question is too complex given you don't know my full tank specs then what is the effective distance covered by a single LED of this type at 20" from the LED with no optics?

Can you use a rio stat to turn the brightness up/down on these LEDs without damaging them?

der_wille_zur_macht
03/22/2010, 01:15 PM
How many Cree XR-E LEDs would you put in each 24" strip to provide actinic supplement to a single 250w MH provided there are going to be 2 LED strips?



How blue do you want your tank? What MH lamp are you using?

If this question is too complex given you don't know my full tank specs then what is the effective distance covered by a single LED of this type at 20" from the LED with no optics?

That's a worse question! "effective" depends on a vast number of parameters.


Can you use a rio stat to turn the brightness up/down on these LEDs without damaging them?

Nope. You need a constant current driver with capability to dim based on an external signal, and you need something to generate that signal. You can't dim by directly reducing the power to the LEDs with a rheostat.

TheFishMan65
03/22/2010, 01:19 PM
You got some reading to dohttp://www.reefcentral.com/forums/showthread.php?t=1678127
Oops the big man beat me to it.

vbsaltydog
03/22/2010, 01:38 PM
How blue do you want your tank?

That's a worse question! "How blue?" is a relative term unless I have a spectrum analyzer, which I don't. :)

Ideally, I would like the LEDs to have variable output so I can "dial in" the desired amount of blue.


What MH lamp are you using?


14K Phoenix 250w DE driven by a Lumatek e-ballast.


Nope. You need a constant current driver with capability to dim based on an external signal, and you need something to generate that signal. You can't dim by directly reducing the power to the LEDs with a rheostat.


OK. So I buy a dimmable driver and then control the output much the same as controlling a servo or stepper motor? Does the controller signal to the driver need to be constant or does the driver hold the output of the last controller signal until it gets a new controller signal without the need of the controller signal being fed constantly?

I plan to control it using a microprocessor so I need to know how to write the program.

der_wille_zur_macht
03/22/2010, 01:45 PM
It'll depend on the driver, but in general they come in a few different flavors. All require a "constant" signal, there's generally no intelligence onboard.

The most common drivers are as follows:

1) Buckpucks need a 0-5v digital or analog signal. They're inverted, such that 5v is OFF and 0v is ON. They can take a PWM or true analog signal over that range. The datasheet shows several arrangements.

2) ELN-model mean well drivers come in two flavors: D-type takes a 0-10v analog DC signal, P-type takes a 10v PWM signal. There are rumors that they're interchangeable.

3) DIY drivers run the gamut. Of the three "popular" designs, all will take a 5v PWM signal.

In other words, it really depends on the specific driver you'd like to use, but most will work in some format that most microcontrollers can deal with.

vbsaltydog
03/22/2010, 01:55 PM
Sounds great. Thanks for the info.