DIY LED driver for reef lighting

I am looking at building some drivers for a nano I have and I am planning on using cat4101 to drive the rebels that are in it if I am reading this right I can only drive 3 leds per cat4101 each rebel consumes 350ma and the cat4101 is rated for 1000ma so I will not quite be driving the rebels fully or am I missing something I was hoping to drive twice that many per string
 
You want to go buy voltage not current. Add the forward voltage, not current. i am not familiar with rebel LEDs, however with cree XPs you can do 6.
 
Funny thing the white led strings driver seem to get about 50 degrees hotter then the royal blue.Anyone noticed this have them running at right at 21.80 volts turning out .69ma on each string. the boards are right around 200 degrees which i think is pretty hot now the royal blues run at about 160 degrees right around the same voltage and .69ma neither has done a thermal shutdown have had running for about 8 hours.
 
Depending on the Rebels you should be able to do 6-7. The driver can handle a MAX of 25v. Each Rebel uses ~3-3.4vF.

3.4x6=20.4

When you are talking about 350-1000mA that is what your are driving the LED too ( Brightness ).

Hope this helps!

-Dave

sanddune600 said:
I am looking at building some drivers for a nano I have and I am planning on using cat4101 to drive the rebels that are in it if I am reading this right I can only drive 3 leds per cat4101 each rebel consumes 350ma and the cat4101 is rated for 1000ma so I will not quite be driving the rebels fully or am I missing something I was hoping to drive twice that many per string
Click to expand...
 
So I would set it up for 350ma for 100% and use pwm to dim and if I use a 18.5v power supply that I already have then I can drive a max of 5 per cat4101
 
Jtro, I noticed the white tend to have have a lower forward voltage at the same current than royal blues (at least the ones I tested). So what is the voltage of each string and the supply voltage (21.8).
 
Its a laptop power supply so no its not adjustable. I would have to buy one or use lm317 to limit the current, on a build this small it shouldn't waste that much. Doing the math if I drive my leds at 700ma if I drive 4 strings off of 4 cat4101 I will need 2.8 amps from my power supply. If the power supply that I am using is 3 amps so I may need to get another or completely different power supply for the whole project. Do you think I will be pushing to close the the limit of my power supply I could under drive them more to get lower as well what do you think the max is that I want to push the power supply.

(talked to the person the built the tank originally and 700ma is what he set it up as and the brightness seems good just not blue enough and not dim able)
 
I am not an expert on PS, and think you may want to find another one though. I what recommended to only use 80%.

i was actually worried about the heat dissipation of the CATs. Lowering the current will increase that.
 
Looking at the ps again and not my notes it's a 3.5 amp this puts me right at 80% so I think I will still use it I am confused on why you say limiting the current will make the cats hotter I thought the closer I get to 17 volts (3.4v x 5) the cooler the cat will run
 
IIRC power supply is 18.5 volts. To run at 17 volts it will dissipate heat energy at a rate of 1.5 volts times the current (say 700) so 1.05 watts. If you make a small change in current the voltage changes at a greater rate. So goto 650ma and maybe a voltage of 16 no it is 2.5 * .65 or 1.625 watts.

NOTE: I made up the number for this example.
 
I am a noobie so bare with me when I said current I think you took it as amps and I was thinking voltage so I want to drop the voltage with the lm317 down to 17 or maybe slightly higher then this although it is good to know that change amps to the cat will lower the needed voltage
 
You are wasting the ecess enrgy as heat. So now the LM317 will get hot. Unless you change the voltage of the supply you must waste the enrgy somewhere.
 
only using 17 volts of the 18.5 should I worry about ruining the cat4101 I know that I will be wasting the energy as heat I am just not sure i want to spend the money for one that is adjustable I also saw some 17.5 volt 1.8 amps supply from ebay for 9 shipped
 
well everything is ordered thanks for all the help I couldnt have been able to fully grasp how to do it without a little help I think I have most of it figured out now
 
i would like to say thx for the excellent thread on diy led driver

i need help on the Eagle pgm to convert the triple cat4101 over to Gerber. I have the freeware Eagle and after the convert i got six files all named cat4101_triple with extension file cmp, gpi, plc, sol, stc, sts

is this correct to send over to seedstudio?

thx
orlando
 
Well I got my drivers in today and they seem to be working only thing is that I seem to get some flicker and they dont stay off should I have a pull down resistor on the pwm pin I was thinking of putting a 10k resistor in place
 
The flicker is probably from over heating -add a heat sink to thd CAT and see if that fixes it.

What is providing the PWM signal. If it is going to ground (IIRC below 1.7 volts) a resistor should not be needed.
 
Its a hydra I used Terahz firmware I notice that it is only 1 of the drivers doing it so I will pull it apart in the morning and find out where I am getting interference I used a heat sink and this started before the lights even turned on so it shouldnt have gotten hot I put my finger on it and it was very cool to the touch I just thought that maybe I was supposed to have put one in and I should have mentioned I only get the flicker when they should be off when they are on they work fine
 
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