perikaruppan
Member
i made 3 boards... so 3 in each will do right?
DIY LED driver for reef lighting
- Thread starter der_wille_zur_macht
- Start date
TheFishMan65
New member
That is probably what I would do. To keep the heat down some.
perikaruppan
Member
20 min they are running the heat is kindda bearable.. but HOT..
only 1 is operational. will run it overnight.. lemme see what happens if it blows or not. if it blows it wont damage the LEDs right?
only 1 is operational. will run it overnight.. lemme see what happens if it blows or not. if it blows it wont damage the LEDs right?
TheFishMan65
New member
I wouldn't think so, but I have troulbe predicting all possibilities.
perikaruppan
Member
ok its 1am now.. will let them run and see in the morning whether it has worked or bursted!!!
Skeptic_07
New member
From the datasheet for CAT4101: "Accurate linear dimming is compatible with PWM frequencies from 100 Hz to 5 kHz for PWM duty cycle down to 1%"
That pretty much means that I can dim down to 1% so long as the PWM input is between 100Hz and 5kHz... right? Sorry for the dumb question....
That pretty much means that I can dim down to 1% so long as the PWM input is between 100Hz and 5kHz... right? Sorry for the dumb question....
der_wille_zur_macht
Team RC
In theory, yep!
Skeptic_07
New member
well thats cool this should work fine for the XP-E's but it only goes up to 1A. I've been searching for a similar version that goes up to 1.5 for the G's but cannot find. I did however find your ncp### that go up to 1.5...... :hmm2:
kcress
New member
Skep; Part of the problem is that these put out so much light that 1% is going to probably still be way too bright for your scheme.
der_wille_zur_macht
Team RC
Just drive the XP-Gs at 1A and buy more of them.
They'll be more efficient that way.The NCP chips get into risky territory near their current limit; at that point you'd probably want to use an external switch which drives the cost and complexity up. You generally can't max the current AND voltage limits on these chips simultaneously, because there's a third factor (thermal dissipation) that'll cut in first.
One way to get around that would be to "mix" your banks of LEDs (i.e. X leds on a given driver spread out over the tank instead of being adjacent). Then you could stagger the on times of each bank to get the effect you want.
Skeptic_07
New member
that stinks!
well... i suppose as close as i can get will have to be good enough..i guess thats one way of doing it! :lol:
what about if i was only going up to around 1250ma and 24V? I never intended to drive them at full 1.5A but did want to go above 1A. I also see they go up to 40V, which is quite a lot but i could do strings of 6 for 24v. I have 36 of each color, which is a good number divisible by 1,2,3,4,6,8,12,18, i had thought ahead in designing stages to be able to change my configuration down the road.
not me man.. I want my LEDs close together so that each part of tank gets blasted at different time... ooohhhh crap i just realized now i dont have enough PWM pins.. CRAP! well.. actually.. no it doesn't matter..
Skeptic_07
New member
do i babble too much ??? let me cliff note that post.. if i was only going up to around 1250ma and 24V on an NCP, will i still have heat probs?
der_wille_zur_macht
Team RC
It would probably be OK. I'm assuming you're talking about running it as a buck converter. You're going to have to design a circuit from scratch, since none of us have run it in buck (that I know of) at that high of current - for instance, some of the components in my original boost design would be over their current limits at 1.25A.
perikaruppan
Member
Vola!!!! it worked and it is still light up!!! 1am to 8am it was ON!!! 7 hours, and not hot at all.. normal it is...
So i guess i hit the optimum operational value.
But one thing, I measure the voltage across each of the LEDs and found this :
the 9 Cool Whites have : 3.69v,3.71v,3.71v,3.76v,3.72v,3.82v,3.7v and 3.7v
the 3 Royal Blues have : 3.82v, 3.81v, 3.81v
Totalling to 42.25V Across the 12 LEDS and supply voltage is at 43.5V, so an efficiency of 94.8%? am i correct?
The current on the system is 620mA. And constant throughout the time of operation.
Tested for 7 hours+ or so...
So i guess i hit the optimum operational value.
But one thing, I measure the voltage across each of the LEDs and found this :
the 9 Cool Whites have : 3.69v,3.71v,3.71v,3.76v,3.72v,3.82v,3.7v and 3.7v
the 3 Royal Blues have : 3.82v, 3.81v, 3.81v
Totalling to 42.25V Across the 12 LEDS and supply voltage is at 43.5V, so an efficiency of 94.8%? am i correct?
The current on the system is 620mA. And constant throughout the time of operation.
Tested for 7 hours+ or so...
TheFishMan65
New member
Depends on how you want to measure efficiency. I would probably user power in over power used. Then comes the question of power in is that to the driver or into the power supply. Either way the part you have control over is very efficient. WELL DONE!
perikaruppan
Member
thanks a ton Fishman and DWZM without your help i think this would have taken me ages.
now the big one - PWM!!! any ideas how i can go about it? going to use and ardunio controller to get it going. have a 1.8k resistor onto a transistor in common emitter mode. the collector is to the ADJ pin of the controller.
By directly sending PWM signals from 0-5V over to teh resistor/transistor module the spec sheet says it can dim the output. The signal required for the Adj pin is between 0.3v-1.25V to control the output. very tiny spread!!!
now the big one - PWM!!! any ideas how i can go about it? going to use and ardunio controller to get it going. have a 1.8k resistor onto a transistor in common emitter mode. the collector is to the ADJ pin of the controller.
By directly sending PWM signals from 0-5V over to teh resistor/transistor module the spec sheet says it can dim the output. The signal required for the Adj pin is between 0.3v-1.25V to control the output. very tiny spread!!!
kcress
New member
Excellent!! Finally!! For the first time someone has reported all the various voltages for a string of LEDs.
+3.82
-3.69
-------
Delta 0.13V over just 8. Parallelers beware.
Congrats perikaruppan, on your success.
der_wille_zur_macht
Team RC
Check the datasheet and copy it exactly - there's a diagram buried in there for exactly what you're trying to do. Basically, it uses the transistor to let the ADJ pin switch between floating (which means it gets the internal reference of 1.25v) and GND. So it doesn't matter that you're "controlling" it with a 5v signal.
stephenrwright
New member
I had had a chance to play with my CAT4101 driver some more, after hooking one up wrong and convincing it to release its magic blue smoke. I tried it on a string of 7 luxeon rebel cool white LXML-PWC1-0100 and a string of 7 royal blue LXML-PR01-0275. With a 768 ohm sense resistor I was getting 680 ma through each string, with these voltages:
White - measured total 21.4v, measured each LED:
3.08 - 3.05 - 3.09 - 3.02 - 3.14 - 3.02 - 3.07
Blue - total 22.3v:
3.10 - 3.15 - 3.33 - 3.11 - 3.35 - 3.11 - 3.21
I had to adjust the input voltage up to 24v before the current through the LED stopped at 680 ma, so the voltage drop for the driver is higher than I expected and the voltage dropped by each LED is lower and less consistent than would have thought. But it seems to work well enough. I set up an arduino to do PWM based on an analog input from a variable resistor and that worked well. I have all the LEDs on starboards mounted on a 1 1/2" wide 1/8" thick aluminum stick, which gets very warm, so I want to come up with a better heat sink so I can do a burn in test.
Over all I like the results and just need to figure how many strings of 7 to put above my 90 gal, 48"x18"x24"deep tank. I had 6 T5HO, so 7x12 would be 84 LEDs total, does that seem reasonable?
Just wanted to share my prototyping fun....
Steve
White - measured total 21.4v, measured each LED:
3.08 - 3.05 - 3.09 - 3.02 - 3.14 - 3.02 - 3.07
Blue - total 22.3v:
3.10 - 3.15 - 3.33 - 3.11 - 3.35 - 3.11 - 3.21
I had to adjust the input voltage up to 24v before the current through the LED stopped at 680 ma, so the voltage drop for the driver is higher than I expected and the voltage dropped by each LED is lower and less consistent than would have thought. But it seems to work well enough. I set up an arduino to do PWM based on an analog input from a variable resistor and that worked well. I have all the LEDs on starboards mounted on a 1 1/2" wide 1/8" thick aluminum stick, which gets very warm, so I want to come up with a better heat sink so I can do a burn in test.
Over all I like the results and just need to figure how many strings of 7 to put above my 90 gal, 48"x18"x24"deep tank. I had 6 T5HO, so 7x12 would be 84 LEDs total, does that seem reasonable?
Just wanted to share my prototyping fun....
Steve
