wich power supply for 8x XP-G on strip (in series)?

Other Types of Lights LED Light Bulbs
1

I got myself this led-strip.
I want to build either a desk lamp or something for my aquarium with it, but the main reason for buying was…you know it… it’s on sale S)

Now I am looking for a suitable power-supply. I’ve got a power-supply from a old scanner (speak:transformer), wich has a claimed output of 30V 400mA. Directly connected to the strip, that would mean 3.75V 400mA per led, right? Will that work or is the voltage too high?

Is there a more or less easy and budget way (I have basic electronic-knowledge and (also basic) soldering skills) to build a adjustable power supply out of it? Putting a conventional 230V dimmer, like for incandescent bulbs in front of the supply for example?? or a big potentiometer parallel to the strip?

Thanns in advance!

2

3.75V per LED is enough for XP-G @ 400mA. don’t connect LEDs directly. add series resistor. otherwise it will draw more than 400mA

try to measure current with few ohms resistor. (2-10 Ohms)

don’t connect conventional dimmer or large resistors with 230V directly.

Running 8 XP-G at 400mA under drive. if me, I use 4 XP-G @ 800mA

3

spec say its 24V @ 350mA
so if you use 30V supply. difference is 6V
add 15 ohm resistor series with LED strip

or LED driver like that

4

You might want to take a look at dedicated LED drivers, too. And don’t be afraid to go above 350mA. Driving a string of XP-Gs at 350mA is almost criminal. They can handle 1.5A if they’re properly heat-sinked. At 350mA, your strip will put out somewhere around 750lm. You’ll get around 1800lm if you increase the current to 1A, assuming you’re able to handle the heat.

Mean Well’s ELN-30-24D LED driver might be a good fit for your light strip. It has internal pots to tweak the voltage and maximum current and it has a built-in dimmer (you’ll need to supply 0-10VDC to the dimmer leads…0V=standby/off, 10V=full power). Downside is it costs around 21USD.

5

Im not sure this would work so well with 8 x XPG’s. The max adjusted voltage is listed as 26.4V, which would only deliver 3.3V per emitter - max. Perhaps the ELN-30-27 would be a better choice. Its capable of delivering 3.7125V per emitter at +1A in this configuration. Your thoughts?

Data Sheet link.

I agree that mean well is definitely one of the much better and safer solution for this application. Being able precisely set voltage and amperage seperatley makes it very attractive.

6

That’s a good question. I think either will work at 1A, actually, unless I’m misinterpreting the XP-G’s data sheet. Interpolating the current-voltage graph, it looks like it only needs ~3.15V at 1A (so ~25V for the OP’s array). That’s within the capabilities of either driver. Perhaps you’re right, though. Perhaps the –27 is a better choice since it’d be operating near its voltage floor while the –24 would be operating near its voltage ceiling.

(What leads me to suspect that I’m misunderstanding Cree’s data sheet is they state that the max drive current is 1.5A and their charts indicate this happens at 3.25V. They also say that Vmax is 3.75V but extrapolating the graph yields a huge current at that voltage).

7

Ive had more than a few XPG’s that have a Vmin lower than 3.30V regardless of Vin (new and used). I should have mentioned that when I recommended the ELN-30-27. When you look at what you get for the price, it still seems well worth it.