how many 10w leds

canadianbudz604 · #1 03-30-2014, 05:27 AM

how many 10w leds can be ran on a cpu power supply
I don't want them to be dimmable or any fancy stuff just to work properly.
I know it runs one 50w led, but how many 10w could I put on it
thanks

Coral Hoarder · #2 03-30-2014, 05:31 AM

Your going to run 10 watt chips on 100% you will burn all ur corals I have them over my 72 and if u
I run more then 70 sps bleach
I would assume 4 or 5 would be safe idk about more

canadianbudz604 · #3 03-30-2014, 06:03 AM

yes 100% but royal blue. I have 10 10w royal blue, and one 20000k. anyone know how many?

mike31154 · #4 03-30-2014, 04:42 PM

Need to know what your CPU power supply is rated at & what the voltage output is. Simple math using Ohm's Law after that. If your power supply produces 50 watts, you could run about 3 to 4 of the 10 watt LEDs on it. Best to have about a 25% safety margin there. If you hook up 5 of these LEDs to a 50 watt power supply & run them at 100%, the power supply won't last long & you'll be risking some fireworks.

How do you intend to limit or control the current to your LEDs? Are you looking to hook them up in series or parallel? I use standard 12 volt power supplies to run my build (parallel), but also have dimmers in line to keep the voltage at safe levels. Different colour LEDs will have a different maximum Vf (forward voltage). Royal Blues usually take a lower Vf & run at less current than the 20000K LED. Exceeding max Vf will cook them in short order.

SeaHorse_Fanatic · #5 03-30-2014, 06:07 PM

I would also highly recommend adding a dimmer function if you're using 10w emitters. I have been using these for about 3 years now and wouldn't think of NOT having dimmers on my set ups, especially for the whites.

canadianbudz604 · #6 03-30-2014, 09:00 PM

Quote:

Originally Posted by mike31154

Need to know what your CPU power supply is rated at & what the voltage output is. Simple math using Ohm's Law after that. If your power supply produces 50 watts, you could run about 3 to 4 of the 10 watt LEDs on it. Best to have about a 25% safety margin there. If you hook up 5 of these LEDs to a 50 watt power supply & run them at 100%, the power supply won't last long & you'll be risking some fireworks.

How do you intend to limit or control the current to your LEDs? Are you looking to hook them up in series or parallel? I use standard 12 volt power supplies to run my build (parallel), but also have dimmers in line to keep the voltage at safe levels. Different colour LEDs will have a different maximum Vf (forward voltage). Royal Blues usually take a lower Vf & run at less current than the 20000K LED. Exceeding max Vf will cook them in short order.

I'm going to hook them up in parallel, I could use dimmers, but I don't intend to use any whites. My tank Is a 40g breeder with a 90w led fixture already. (This is a dimmable fixture) with 15 6500k Cree and 15 blue Cree. Could I use resistors? Or should I just dim them?

mike31154 · #7 03-30-2014, 09:27 PM

Either or none will work. The key is not to exceed the Vf and/or rated current as I mentioned in my earlier post. The specs for the 10 watt Royal Blues I have is 9 to 10 volts Vf and maximum current of 900 milliamps. The standard blues & whites have max current of 1000 milliamps. Warm whites are down at 900 milliamps like the Royal Blues. The output voltage of your power supply will determine what current the LEDs run at if you don't use any dimmers, resistors or other current limiting device to protect them. Therefore you want a very stable power supply that has a Vf of about 9 volts. Lower voltage is probably better. Due to manufacturing variances, it's likely that each one of your LEDs will run at a slightly different current when provided with the same voltage if you don't use a current limiting device. That's why most folks opt for constant current drivers instead of a constant voltage power supply.

I use fairly inexpensive dimmers to keep my Vf less than 9 volts for all colours of LEDs I'm using in my fixture. This provides a bit of a safety margin from premature burnout. Early in the build I did some current testing & found that there was as much as 80 milliamp difference in current for some of the LEDs when provided with the same voltage. Photo of the dimmers & power supplies follows. I actually cooked the RB dimmer recently but looking back I wonder why it took so long. I've been running too many LEDs on the two dimmers running my outer rails of LEDs for a couple of years now. There are 9 LEDs per rail, so the 8 amp dimmers have been running at close to maximum rating. The two dimmers for the center rail run 4 and 5 LEDs respectively, so they're well within their rating. I have 5 more dimmers on order & will be splitting the load so each outer rail is run the same way as the center one. So the photo will have two more dimmers added below the two on the left. Not sure why the RB dimmer cooked before the 10000K one since it runs 8 LEDs while the 10000K runs 10. Only thing I did was install a couple of larger power supplies recently. Also been running the voltage at 8 to 8.5 for a while now, not as low as the settings in the photo.