First time building an LED :)

[Bennell]

Hi all,

First post here after a while of lerking and reading some very good info i've decided to join up

Anyway, im building an led bar for the first time which will be for aquarium use - i say building, im more modifying what i have.

The light i have is a Roleadro 81w (27*3w) red and blue hydroponics grow light see link to full description Roleadro 85cm Led Growing lamp Strip Bar 81w with Red and Blue lights for Hydroponic: https://www.amazon.co.uk/dp/B00YTWMSNM/

Apparently they are 3w leds- Epistar copy i imagine consisting of Red (610-660nm) and Blue
(400-520nm)

Im looking to change a fair few of the leds to suit my needs which isnt a problem in terms of soldering etc. But i have a feeling that the leds used, arent actually 3w due to the figures stated on the power supply - how could i check?

The output on the psu says 20-31vds at 1.2A but my understanding is LEDS should be in series with constant current of the LEDS max forward current
So 1.2a sounds too high unless they have resistors for every 3 or so leds?

One thing i did want to change was the wattage of the LEDS and if they are 3w, i would change them to 1w, is this do-able? If there are resistors in line per X amount of leds, to regulate the current whould this cause an issue?

I will upload pictures of the ligts, pcb etc. once photo bucket starts to behave and apologise for the lack of info

Thanks

Joe

 

[evilc66]

Based on the information you have given us so far, it looks like the fixture is split into 3 series strings of 9 LEDs, with each string run in parallel. That will give you about 400mA per LED. Changing to 1W LEDs doesn't make any sense in this case, unless you replace the constant current power supply to something that will supply about 900mA total with the same voltage range. Anyway, 3W LEDs will be more reliable at the factory currents, and are more readily available.

If you don't need the power of 3W LEDs, then you may want to consider getting a driver that is dimmable. At least then you can adjust the output to suit, and the 3W LEDs will live a lot longer and produce less heat.

 

[Bennell]

evilc66,

thank you very much for your reply, and dimmiming them would be the ideal solution i was under tue impression i couldnt dim them as i did buy a cheap pwm dimmer off eBay but all that did was cause the leds to flash :/

So if i purchased a driver with the same ratings but dimmable, that will possibly work?

Thanks again.

P. S. I will be opening the light up tonight so will be able to provide much more imformation

 

[evilc66]

Yes. There are many options for dimmable drivers. One such option is the Meanwell LPF-40D-36. That gets you in a similar current and voltage range, and can be dimmed by a few different methods. They are pretty reasonably priced too at about $23

http://www.mouser.com/ProductDetail/Mean-Well/LPF-40D-36/?qs=8LJq9%2bybq8owtre1fUaUtg==