DIY LEDs - The write-up

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Has anyone had / noticed a light pulse after turning a meanwell driver (ELN-60-48D) off?

I finished the 3rd 12x string last night. 1st string is 12 xp-e royal blues, 2nd string is 12 xp-g (6nw/6cw),
and the third string is 12 xp-e royal blues. This last string comes on fine, dims OK, but right close to 7 seconds after I turn the power off I get a light pulse. The other two strings didn't pulse when I tested them. I checked and found no shorts to the heat.

Any thoughts?

Thanks,
Randy

I've had that on a couple...a single blink when the power strip is turned off. Once put on an APEX there was no blink.

One thing to note if your forward voltage does not match the driver it makes a nice christmas tree light by blinking regularly.

Make sure you check the mA of the 48D and adjust the output. I measured one at 1.8A :strange:

Bill
 
LED Optics Test

The test fixture is a 24" LED Strip Kit custom assembled for Corbins Exotic Pets Pets in Buffalo Grove Illinois.

The Heatsink is a 24" x 8.46" from HeatsinkUSA. The LED strips are 6 XR-E Royal Blue/White and 4 XRE Royal Blue. The drivers are MeanWell 60-48D. The four Royal Blue strips are driven at full power (at 9 volts appx 580mA) in 2 parallel series of 12 LEDs. The other Royal Blue/White Strips are driven by a single MeanWell 60-48D adjusted to 750mA at 9Vdc

What brand optics were used? It looks like the 70° is the winner to me.
 
LOL.... When typing the post ya think ya put in all the details......!

The menawell's for the blue's are at 800 ma by digital multimeter and 1000 ma for the white string. With a 2:1 ratio I thought the blue should be run a bit higher than 700 ma and I picked the 1000 ma setting just for the nice even number (I'll drop it downward if I want a more blueish look).

Also I was testing one string of LED at a time. In the time since I posted, I've rewired so that all strings are on at once. NO Flash after turning off. So I guess I'm OK. I'd still like to know what causes it though.

Now that I've a decent camera I've really got to learn how to add pictures.

Thanks,
Randy
 
Need some input on this little rig. Lets say I have Royal Blues and some True Violets on a meanwell ELN 60-48D driven at 1000mA. The True Violets has a max of 500mA. If I do this is ok? All LEDs in series but the true violets in parallel hoping to reduce mA down to 500

LEDstrip.png
 
In theory it will work. Ideally you would want a fuse. If one of the violets open all the current will go through the other and it will blow. Also if the Vf don't match you may get 450 and 550 so maybe only run at 900ma total (or 3 in parallel - if one goes two are still in parallel and don't go bye-bye).
 
Just a quick note on some of the driver issues and finding cheap ways to do it. This is specifically to address (or just add to) kcress's post from about 20 pages back... sorry it's a bit of a necro.

There is an adjustable regulator which can be had for about $1.00 called LM317. This has 3 pins IN, OUT, and ADJ (adjust) and can run over 30 volts at 1.5 amps. This is perfect for driving those 6-LED strings at 24V. You simply wire a 1.25 OHM resistor to the OUT line, and then the LED after this. The ADJ line is tied between the resistor (just after it) and the first LED. This gives you a 1amp CURRENT controlled regulator. Double to resistance, and you halve the current... easy math. You can then look at potentiometers instead of resistors for fine control.

The advantage here is that you should really have a current controlled driver, and the I-V relationship in LEDs is highly nonlinear. A small change in voltage makes a very large change in current which can quickly run away and kill the LED. The second thing.. a blown LED (short) will cause an increased current flow in a voltage controlled source, and could blow the rest of the string. Better than a fuse, this source will still drive only 1A, even if 2 blow. A simple resistor will start running the remaining LEDs too hot in this case, and may take them out too. The driver basically acts a resistor that changes is resistance to makes sure that the resistor always has a 1.25V drop across it which is 1A for 1.25 Ohms, and therefore the LED string will always run a 1A... This also lets you reduce the power dissipation of the resistor (1.25V x 1A = 1.25W). The LM317 also has internal current limiting and temperature sensing, so it will shut itself off before it fails in case anything goes wrong. This makes the circuit more fail-safe and even cheaper.

Another idea for those trying to make dimming circuits is to use PWM. This essentially turns power on and off rapidly, giving the effect of dimming. This can be done very easily using a micro-controller and a power MOSFET. The MOSFET (520N for instance) can typically handle 10A, more than enough and is again $1-2... but what if you don't have a microcontroller? There's another simple and cheap circuit you can use.

The idea is a little more complex, but still easy to do at home. The well-known 555 timer can be used to generate a "sawtooth" wave, basically a triangle wave instead of square or sine waves. That output is fed to one side of a comparator, which simply a switch than turns its output on and off based on which of 2 signals is larger. The other side of this comparator gets hooked to the center tap of say a 10k potentiometer which is wired to the supply and ground. The output of the comparator is the finally hooked to the gate of the MOSFET. Lets say we set the potentiometer half-way up. The triangle wave will then spend half its time below that voltage and half above it. The means that the comparator, and therefore the MOSFET will spend half its time on and half its time off, which leads to 50% output on the LEDs. This gives two big advantages... The first is that for those using white LEDs or various different colors of LEDs, the color drifts ALOT less when using PWM dimming... and yes color does depend on the output due to a different temperature of the LED. The second is that the same triangle wave can be fed to any number of comparators, and you can get up to 4 or even 8 comparators on 1 IC, which means very little additional investment to control multiple colors and/or channels.

I've attached a sample circuit diagram for the sawtooth oscillator for you, but triangle waves work equally well. The frequency is almost unimportant for this application, something between 100Hz and 10kHz will be fine, so component selection is simple. For the comparator an LM339 is both cheap and effective.

picture.php


For a total price of around $20 you can build a 4-channel control system and driver sets for almost as many LEDs as you could possibly want to run (plus the price of the 24V power supply) and have flexibility and fail-safety. A little more complicated the kcress's design but still easy, even cheaper and a makes me feel a bit more secure. You may not want to tackle PWM, but I high recommend you try a real current-limited supply instead of a simple resistor, its only 1 extra part.
 
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Foxy, not sure what you are geting at. But have you read the DIY driver thread? For About $1.50 you get the LM37 functionality and PWM that you described above. All you need is a sense resistor (ok the math is not as simple) and a couple capacitors. Still need the 24v supply.
 
Quick question: how many Cree XR-Es can be ran in series on one Meanwell ELN-60-48-D? I know 12 is usually the way to go but I think I've heard up to 15 can be done safely. True?
 
Foxy, not sure what you are geting at. But have you read the DIY driver thread? For About $1.50 you get the LM37 functionality and PWM that you described above. All you need is a sense resistor (ok the math is not as simple) and a couple capacitors. Still need the 24v supply.

Nope, I've not read that particular thread, though I would be interested if you can link it. The idea here was to provide a super simple (2 parts), cheap ($1), high current (1.5A), and current-CONTROLLED supply (ie. fail-safe and reliable). I also wanted to give a very simple and cheap way to generate the PWM signal for those less than comfortable with programming micro-controllers, and one which can control an almost unlimited number of lines, whereas a uC can at best do only a few.
 
Need some input on this little rig. Lets say I have Royal Blues and some True Violets on a meanwell ELN 60-48D driven at 1000mA. The True Violets has a max of 500mA. If I do this is ok? All LEDs in series but the true violets in parallel hoping to reduce mA down to 500

LEDstrip.png


I like Fish's (3) idea. I'd also include (3) 0.1 ohm 1/2W resistors in series with each LED so you can make sure nobody's hogging the current. You should buy a few extras so you have some to swap in.
 
Quick question: how many Cree XR-Es can be ran in series on one Meanwell ELN-60-48-D? I know 12 is usually the way to go but I think I've heard up to 15 can be done safely. True?

The guys at Mean Well use an assumed 3.5 forward voltage for the Cree XR-E (yes it has been rated at 3.2 depending on how its driven).

The ELN 60-48D has a voltage range of 24-48 so 48/3.5= 13.71 LEDs.

I like 12 just because but theoretically no harm in adding a single red or green to the mix.

Bill
 
Foxy
Here is the link: DIY LED driver for reef lighting
It takes a few pages to get to the CAT4101.

There are a few problems with that chip, though it is a nice one.

The first one is that at 1A you are right at the rated capacity. In reality you shouldn't run such things beyond about 0.7x the rating, unless it has VERY good heatsinking.

This is exacerbated by the second problem. SMT only! While some folks don't mind hacking a toaster oven into a reflow station to work with SMT chips (I have one of these) most people don't want to cope with that. You COULD hand solder it down if you had the proper PCB made ($$$) but even then you wouldn't be able to get the back of the chip soldered to the ground plane for heatsinking unless you reflow.

Put together it means you wont be able to hit 1A true output for long unless you spend some serious money on equipment and custom PCBs. Using through hole components like the LM317, with much higher current ratings means no heroic measures to put the circuit together and get 100% output from the LEDs. Heck, you don't even NEED to solder, just wire wrap.

I'll stick with my drivers, thanks.

The second part is how you can get that PWM signal without a microcontroller, which I hope will be useful to those who don't want to spend $20-40 for an arduino with only a couple PWM outputs. This can do MANY output (dozens), and can even convert that 0-10V DC output from your current aquarium controller (profilux or whatever) to a PWM signal, by simply comparing that instead of the potentiometer voltage to the triangle wave. That way you can build you own drivers rather than buy the Meawells.
 
I will do a quick response, but if you would like to discuss it more lets go to the right thread to discuss the design.

1) These can be run in parallel so you could use 2 to reach your desired 1.5 amps. But since most are running below 1 amp it seems to be a good choice.

2) This a huge smt part and soldering the back plane is not a problem. Many have done it including me. My PCB is about $10 and wll hold 8 chips for 48 LEDs. Not sure what the three chip version is running.

3) It takes a 5 volt PWM signal so the same 555 circuit should work that you described above.
 
I will do a quick response, but if you would like to discuss it more lets go to the right thread to discuss the design.

1) These can be run in parallel so you could use 2 to reach your desired 1.5 amps. But since most are running below 1 amp it seems to be a good choice.

2) This a huge smt part and soldering the back plane is not a problem. Many have done it including me. My PCB is about $10 and wll hold 8 chips for 48 LEDs. Not sure what the three chip version is running.

3) It takes a 5 volt PWM signal so the same 555 circuit should work that you described above.


If I wanted to get one of your PCBs, where could I find one? 8 of those is about right for the tank I'm building.
 
Foxy, the CAT4101 essentially fills the same purpose as you are proposing the LM317 for - they're both linear regs that can be run in constant current mode. The big differences are that the CAT4101 is made to accept a separate PWM control signal, so you don't have to PWM the power line yourself (which is probably not as simple as it looks if you want good control) and, even more importantly, the CAT4101 has a .5v minimum dropout, while the LM317 is something like 2.5v. This means it'll run more efficiently, and it'll be easier to run it "hard" (near it's current limit) without needing heatsinking. An LM317 run anywhere near it's 1.5A current limit needs a HUGE heatsink PLUS active cooling PLUS careful PCB design PLUS an ideal environment. A CAT4101 run at 1A only needs heatsinks or active cooling if your PCB sucks or you're running in a bad environment.
 
small LED setup

small LED setup

Hi all. I've been lurking in the DIY section for a while and made a few posts with questions a while back. I thought since most I"m seeing are these very large builds, I thought I would just show my very ghetto small LED build for my 5 gal tank.

Please excuse the very dirty tank :)

I have 6 CREE LEDs on there, it is driven by a 700mA buckpuck. The circuit is still on a breadboard because I am planning on eventually adding a PWM microcontroller (perhaps a PIC?) The heatsink is some old part salvaged off of an computer. The yellow box is a 24V 2.5A power supply. There is a pot on the breadboard currently for adjusting the light.

picture.php
 
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