Hi I have a constant current led driver:1000mah 35v 30-35w. The voltages and total wattage are correct for what I need but the current is too high (the led's are 700-800 mah max rating) I have a Mean Well LDD-700L unit, will this, in series, limit the current allowing me to run the led's? Thanks in advance.
You would not put that in series. The LDD is a driver, so you only would need that (and a power supply for it). An LDD is not a current limiting device or anything like that
Many thanks for swift reply Turbo, is there any way that I can use the 1000mah driver, say with resistor in series? Or do I have to bin it and get a DC power supply?
Yes, you can get a resistor that will do the trick. Has to be a high-power one, I haven't ever really done that so I can't give you much insight except that the load-shedding resistors look like a stick of concrete about the diameter of a pencil, with wires coming out of them
If I were to do that, how would I calculate the resistor value? Isn't that a waste of power, or is it negligable loss? And is the cheapest way, given that I have the LDD700L to just get a power supply that's 35w and 35volts?
I suppose I should ask: what power supply (made by meanwell should I get considering I have the LDD700L)? I had a look on Ebay and I see power supplies for LED's then I see some similar and they say LED driver, I don't know the difference. Sorry this is all confusing.
LPC-35-700 is constant current driver is 700mA, 48V, 33.6W which is plug & play - just connect the output leads directly to your string and it puts 700mA of current through no matter what the total voltage drop is, up to 48V. I think it has a minimum Vdrop of like 10V or something. It's all in one, so you just put a plug on it (universal voltage) and you're off to the races. The LDD is essentially the inner guts of the LPC without the built-in power supply. That version is meant to incorporate into a circuit board that is supplied with power. So LDD + power supply = LPC, essentially This is actually trickier than I said. Since you have a 1000mA constant current driver, what you would need to do is put the resistor in parallel with the string so that you split the current between the resistor and the LEDs. This will be difficult because the LEDs don't have a constant resistance as this changes as they heat up, age, etc. The "power resistor" scenario I was thinking of only works if you have a constant voltage power supply, because you want to drop the voltage across the resistor, and that is V=I*R, much simpler. I wouldn't attempt to build a current splitter and use the 1000mA power supply to try to get 700mA of current to the LEDs.
Arghh I've spent money out on drivers thinking I had it worked out and all along there was a cheap alternative that matches! Never mind. I've got the requisite info now, and for that, I thank you Turbo. Part of the problem is the forward voltages and max operating currents, as I've mixed and matched different LED's and some are 700, some are max 800mah, but I don't mind, I'll just run the 800's at a slightly lower level. This new array I've got planned is to light a chaeto bundle in the sump, so the slightly lower output of the 800mah LED's aren't going to matter.
