LED lighting on a budget!

[widmer]

That's quality Kcress. Now all we need is for the LED's themselves to drop by half in price

 

[kcress]

Nice write up, simple and easy to follow :beer:

Thanks spc1spc1!

Your drawings and parts sourcing make this project appear very doable. Would the terminal strips, fuses, and resistor portion be best mounted in a project box?

sphil876p; The resistors will give off about the same heat as one of the LEDs so they need to be somewhere they can breath. However they're allowed to get a LOT hotter than the LEDs. You can put them about anywhere they can have flow including only convection. I'd probably be a cleaner install if they were mounted in the hood with the LED strings. I'd probably put them and the fuses all in the same area with some airflow. Perhaps under the splash shield.

WOW! I would like to hear some comments for some other DIY electrical guys! Very well written - if this is for real I may have just found my next project!

This is really as simple as I've stated it. There is nothing to discover. I'm just reminding us all that we don't have to use expensive drivers unless we require individual string dimming. Personally I'd probably start with this setup, and if I needed to, switch to dimmable strings later. You can use the already existing screw terminals to simply switch over.

This is fantastic.

kcress, can we do a cliff's notes of advantages and disadvantages of this approach over regular drivers? I'm not sure I'm picking it up correctly.

Advantages:
1) Cheaper than commercial products
2) Less electrical noise
3) You have full control, since you built it

Disadvantages:
1) No dimming or controllability (could it be added without getting too complex?)
2) Is there potential for inaccuracy if the resistor or power supply drift?

I need to do a thread on my DIY drivers. It's interesting that the cost ends up being almost exactly the same as this solution - but you get controllability, at the tradeoff of a far more complex circuit.

Thanks very much

Thanks der_wille_zur_macht and for your great support to all the posters here.

Your Dimming point. Yes you can dim with this system but you have to do it by dimming the entire system with a voltage change at the supply. Well you could actually do it with some Frankenstein giant rheostats or something but eeeeeuw.

As to your drift question. Certainly, but I would expect only a few percent. Noting you could see and possibly similar to current drivers themselves.

cool write up :thumbsup:

Thank you tntneon.

not only does your explanation broken down in steps make it easy to understand, it should be easy to modify the thought process to fit an individual's needs for their perticular setup & the visualizations make it easy to understand as well....EXCELLENT (/bill & ted) LOL

my next build i will be on the smaller side, so i'll have to do a pre-build pricing breakdown to see if the savings will be substantial enough versus just buckpucks

Thanks james3370! Yes that was my intent to show people how to do any size rig not just a "60". This would work for a much smaller or larger layout.

thanks kcress for the informative post

You bet Skeptic_07!

kcress,

Nice find on the resistors!
I was using some of those AVT-200s just the other day intentionally burning some stuff up in the lab.

Very nice write up! Extreme detail ( We should get paid for this stuff )Stu

Thanks stu. Yeah these things take a heck of a lot of time to write! As I do them I marvel at people who write frikken books! Yikes!

Yes I started out looking at small power rheostats thinking they would be most easy to adjust but in multiwatt varieties they cost as much as drivers!!!

Then I found these and started to realize they were higher power, smaller, and more robust.

WOW!!!

Yes it was worth the wait.

60LEDs and only 100 in parts, yeah baby.

Thanks for the kind words shackscs. $100 PLUS LEDs! But hey if you save $150 over drivers how many more LEDs can you buy? :celeb1:

So since I am no electrician and simply have to take people's word for it when they explain a DIY like this, do we have any pics of ones of these babies in action for those like me who like visual gratification? :LD

Not yet. :jester:

That's quality Kcress. Now all we need is for the LED's themselves to drop by half in price

Thanks widmer! Hey, they're semiconductors they dropped a few more cents in the time it took you to read this behemoth!

 

[hayes112]

here is a little info i found on them..sorry 1.5watt..
1.5W High Power Module-White
Operating Voltage Rated Current Rated Power Dimension Viewing Angle Wavelength Luminous Intensity LED Amount Waterproof Feature
12V DC 120mA 1.5W 28×28×12mm 120° "” 65-70 lm 1 IP65

Can you tell me where you can get these I wouldnt mind trying these on a nano setup.

 

[eznet2u]

IIRC, you are using the symbol for a variable resistor after the power block/fuse.
For dimming capability, couldn't you just add the fixed resistor where you show the
variable and add a variable before the fuse?
This should allow for dimming of each string.

Please correct me if I am wrong, it has been awhile since I took an electronics class.

 

[eznet2u]

Oops, sorry. The symbol is for a potentiometer not a variable resistor.

 

[kcress]

Hi eznet2u.

Not sure I'm following your;

This should allow for dimming of each string.

Anything before the fuses would not be string changing but would change ALL the strings.

You can not really use fixed fuses for several reasons. One is that due to the variation in the string voltage stack-ups no two strings will be the same. So what value do you purchase for each string?

Next, you can't buy 4.37 or whatever ohm resistors that you might find you need. That's why you roughly set the resistor then check and if necessary adjust.

My drawing is sort of a modified "field diagram". A field diagram tries to depict things as they appear visually, unlike a schematic that depends entirely on standard symbols. With that in mind my drawing actually shows what those variable resistors look like and at the same time schematically what's happening.

 

[eznet2u]

So, this would not work?

 

[eznet2u]

Sorry for the poor quality...MSPaint bites.

 

[kcress]

Yes! With the following points.

It looks like your plug is for a wall outlet which has no + or -.

You show a transformer and not a power supply. Which could work if more components are added.

The variable resistor would need to be correctly rated for the power it ends up dissipating.

If you are talking about making the after-fuse resistor fixed then I think you will have serious issues with accidentally over driving the string when your variable resistor is turned to its lowest resistive value since you weren't able to adjust the 'after resistor' to limit the maximum string current.

 

[xcracer]

what about the voltage drop on leds.. like when they become hotter their voltage tends to drop...

what about one step up from a resistor.. a LM317T

 

[kcress]

Hello xcracer. There will likely be some slight changes in the string currents with the LEDs changing temperature during warm up, and with the heat sink warming up. However it will stabilize and be quite constant once warm up is complete.

Keep in mind that if a string changes from 700mA cold to 680mA hot you aren't going to see a difference. That's like a another drop over Niagara Falls. If it really bothers someone these are variable resistors! Just adjust to the current of choice - hot.


The problem with LM317s is that they are sensitive to power levels. If you exceed their power rating because your string has a low string Vf or your supply voltage is high they will start blinking to their detriment. They will have to be correctly mounted to the heat sink to function at all and they require soldering to flying leads with can be a challenge for some. Also they need some setting resistors.

One can certainly use them though.

 

[Danielrvb]

Your absolutely right in that I should take a look at this. This is perfect for what I want to do. Cheapest at functioning as possible! Truly, with the exception of people wanting to do sunrise and sunset, I dont see why any basic LED DIY would not do it this way!

My only concern as I was reading was efficiency as I had read early that resisters were not the most efficient way to go. But with you pointing out its a mere 2-5% difference. I am not worried about that at all.

I particularly like that you can adjust your levels with this. I would have gone with out dimmers for cost, but was concerned about if I would be displeased with the results with out, and again this takes care of that.


And one thing to just confirm, when getting dimming capable drivers on the other setups. The dimming is just done with changing the amps correct? as you adjust your dimmer, its just making adjustments to the amps the leds are pushed at correct?

 

[DidYouSayReefer]

So 60 LEDs will cover how much square footage? Are we talking this is good for a 4' tank and what kind of par?

 

[Cramz07]

what about the heat sink dosn't that need to be added into the cost or some way of removing the heat?

 

[Cramz07]

also when thinking of fans how would i figure that extra load onto the power supply?

 

[der_wille_zur_macht]

And one thing to just confirm, when getting dimming capable drivers on the other setups. The dimming is just done with changing the amps correct? as you adjust your dimmer, its just making adjustments to the amps the leds are pushed at correct?

Effectively that's true, but it's implemented in different ways with different drivers. Some constant current drivers just turn themselves on and off rapidly, adjusting the duty cycle, to accomplish dimming. Usually this is in response to a PWM input into an "on/off" pin that controls current through the driver. Other drivers truly adjust the output current target in response to a dimming input. Often, this is implemented through adding or subtracting voltage onto the current sense portion of the driver circuit, which "tricks" the driver into working at a different (lower) current.

So 60 LEDs will cover how much square footage? Are we talking this is good for a 4' tank and what kind of par?

60 typical LEDs (Q5 Cree XR-E mixed 50:50 with RB or blue run at 700mA) would be plenty for most average 4' tanks (75g, 90g, etc.) Roughly comparable to two 250w MH.

what about the heat sink dosn't that need to be added into the cost or some way of removing the heat?

Absolutely. Many people use the mega heatsinks from heatsinkUSA, but with careful planning there are cheaper alternatives.

also when thinking of fans how would i figure that extra load onto the power supply?

Depends. The easiest way to implement fans would be to just use a 12v wall wart or other separate power supply. If you want to wire them to the same power supply as the LEDs, you definitely need to take their load into account, and of course ensure that the PS will give them a reasonable voltage (i.e. many people are using 24v supplies, you wouldn't want to put a 12v fan on that!)

 

[kcress]

Thanks DWZM for handling these questions in your usual clear and accurate manner.:thumbsup:


Let me add a suggestion for the heat sink aspect.

A correctly designed passive heat sink system that supports any particular design has its heat removal ability at least tripled by added mechanically moved air (a fan).

A correctly designed passive heat sink system is very tough to do for our aquarium lights because the heatsink orientation is exactly wrong. The fins invariably run perpendicularly to the local gravity. This messes up convection and how it would normally provide for heat transport.

It means we need to incorporate fans to augment our heatsinks.

Once we've added fans we no longer need massive heatsinks if we correctly design the air flow path.

Correct air flow means we make sure the air moves over all of our cooling material in a uniform way.

This means tagging a fan or two on after everything else is done - does not cut it!

The least expensive way to do this is to use aluminum angle stock. (think 'angle iron') Alternatively just bend aluminum sheet strips into the same shape.
You can go to a local mechanical contractor and have them make these up if desired. Use sheet aluminum that's about 16 gauge give or take a little.

Mount all your stars along the face that will point down. You will generally want to orient the angle the long way down you tank's face. That's side to side as apposed to front to back.

Mount these strips next to each other front to back.

You must now enclose them all in a box that's close. The fins should make fairly air tight channels. You need to make the box extend to the sides a few inches.

Now you put in fan cut outs on one end and mount multiple fans as needed along the end. Have them blow outward. On the other end you need to put a uniform number of holes. Preferably a large one centered in each channel. This is to make sure air reliably comes down each channel. The extra space on the fan end makes up a plenum chamber to help provide uniform 'draw' down each channel. If you use a lot of fans you can run them slow and prevent noise issues.

This method takes a little wood working ability to pull off. This isn't all bad as often something is needed to enclose the fixture for aesthetics anyway.

 

[bstohrer]

You could probably accomplish the same thing by using square aluminum tubes. I've also been bar stock in an enclosed 72" canopy (135 gallon) with 6 or 8 fans blowing air toward the front thereby forcing hot air out the back between the fans.

 

[Danielrvb]

Anyone have ideas yet on something cheaper then HeatsinkUSA? I wandered around home depot the other night. While I did fine some aluminum L shaped rods that may potential work. I did not find much else, not even the U shaped ones I have seen discussed one some other thread.

 

[der_wille_zur_macht]

Look through your yellow pages for a metal supply shop, or look online:

http://www.onlinemetals.com/merchant.cfm?id=62&step=2&top_cat=60

http://www.metalsdepot.com/products/alum2.phtml?page=sangle&LimAcc=$LimAcc