advanced wiring question....led driving

james3370

Premium Member
ok, for my led lighting for a build i am planning, i want to have (3) blue leds for moonlights & (2) white leds for fuge/cheato light. since they will be on the same light schedule (opposite main lighting), i was thinking about 1 driver/power supply to simplify everything, but can't figure out the easiest way to do it since i really need the whites to be full power, but the blues to be dimmed down so they aren't as intense......

the only way i can come up w/ to do like i'd like to do is this:
* 350ma dimmable buckpuck>>blue leds
* 700ma non-dimmable buckpuck>>white leds
* either 1 or 2 wall adapters....depending on what i can find to meet votage/amp requirements

but that seems excessive as far as $$ having to buy 2 seperate buckpucks for no more than they will be doing (trying to save some $$ ya know LOL)

the other thought i had was this:
wall wart (voltage/amperage to be determined)>>700ma standard buckpuck>>white leds in series>>resistor (value to be determined)>>blue leds in series>>return to buckpuck

i was thinking (5) total leds(3 blue & 2 white) w/ forward voltage of 3.5 each=17.5v & i have a 20v/1a wall wart.

so for all you electrically gifted individuals..... will that work??
 

insane

New member
A simpler way to dim them down

A simpler way to dim them down

The easiest way to do what you want involves no electrical work and is relatively inexpensive to do.

Run full power to all LED's

This is assuming you are in Nashville like it says under your avatar.

Go here.
Guitar Center Nashville
721 Thompson Lane
Nashville, Tennessee 37204

Phone: 615-297-7770
Store Hours:
Mon-Fri: 10-9 | Sat: 10-8 | Sun: 12-6

Ask for Porter, he is off mon & fri
He works 1pm til close.

Buy a Half Sheet (21" x 24") of this for $6.95 + tax:
http://www.leefiltersusa.com/lighting/products/finder/act:colordetails/colorRef:C4630710C73DB0/

You want True Blue #196 Lee Color Filter (gel) or one lighter in color. Hold it up to a bright light at the store and look through it, either the whole sheet or a swatch book they should have, to get an idea of how dark it is. Stay away from powder blues (pukey looking), opaque blues (frosted or hazy), and ones with any hint of red tones in it or you will end up with purple LED's. If it looks purple or lavender don't get it.

Do not go darker than True Blue #196.

Cut a small piece to fit over each Blue LED you want to dim down. Attach it with double stick tape or similar. You will get the idea once you start using this stuff. Try it with one layer on each LED first. If that is not dim enough, add another layer. You can add as many layers as you want. That is why you go with the lighter shades of blue. These are designed to be placed within 8" from a 1000w lamp in a large stage light without melting.

This can also be wrapped around a normal output flourescent. Do not use it on the other kinds of flourescents. Do not let it directly touch a regular, halogen or MH bulb. If you heat this up too much you will melt it and it will curl and come in contact with the lamp if it can.

This will save you from having to wire this to that and the other thing and will let you dim down the LED as low as you want. If you get it too dark with too many layers, simply take one layer off.

Lights not 2 Brite by,
insane
 

kcress

New member
If you want to do it other ways we can.

Since you don't want the full whammy on the blues you could just run a wall wart and an appropriate dropping resistor.

Alternatively you can run them all in series but add shunt resistors across the blue ones. That way the full 700 won't be running thru them.

Or run 4 blues, two in parallel, twice.
 

JTL

New member
I have heard that brilliance and insanity are 2 lanes on the same side of the street. :spin2:
 

james3370

Premium Member
<a href=showthread.php?s=&postid=15417855#post15417855 target=_blank>Originally posted</a> by kcress
Alternatively you can run them all in series but add shunt resistors across the blue ones. That way the full 700 won't be running thru them.

yeah, that is kinda what i was interring by this configuration....just didn't know the terminology LOL

wall wart (voltage/amperage to be determined)>>700ma standard buckpuck>>white leds in series>>resistor (value to be determined)>>blue leds in series>>return to buckpuck

* how do i figure out the value of the resistor(s) i'd need??
* can you give me a laymans description of how i'd wire it up??
i'd assume that since it is "shunting", the negative off the last white led going to the positive of the 1st blue would have a resistor wired in going to the negative coming from the last blue led going to back to the negative of the buckpuck?

sorry, my electronics skill level as far as reading schematics & knowing all the terminology is minimal....but i got the basics & can usually figure it out once explained LOL
 

james3370

Premium Member
<a href=showthread.php?s=&postid=15418112#post15418112 target=_blank>Originally posted</a> by JTL
I have heard that brilliance and insanity are 2 lanes on the same side of the street. :spin2:

i've always said that going crazy seems to be the only thing that keeps me sane
crazy.gif
 

JTL

New member
<a href=showthread.php?s=&postid=15419267#post15419267 target=_blank>Originally posted</a> by james3370
i've always said that going crazy seems to be the only thing that keeps me sane
crazy.gif

I was thinking about the way Insane (Frank) would do it. He may be brilliant but is also insane. At least he claims to be.
 

insane

New member
<a href=showthread.php?s=&postid=15419491#post15419491 target=_blank>Originally posted</a> by JTL
I was thinking about the way Insane (Frank) would do it. He may be brilliant but is also insane. At least he claims to be.
You think that is something, wait til you see what I put together today and posted a link to it in the equipment forum about LEDs!



ha ha ha ha ha (crazy laugh)
insane

[violation]
 
Last edited by a moderator:

JTL

New member
I don't know much about aquarium lighting. No scratch that. I don't know anything about it except that the fixtures are insanely (no offense) expensive. They are even pricey if you buy the components and DIY. From what I read it is all about PAR. It would be interesting to measure that with the fixtures you use in the clubs. I like the fact that they have enclosures for mounting and look kind of neat.
 

insane

New member
It seems that a moderator on here is playing games and deleting posts of mine. The one I made in the equipment forum this afternoon is now gone about the LED fixtures. Isn't that nice. I actually paid for premium membership too. Several others have disappeared on me before as well.
 
Insane, if you have questions regarding a moderator's actions, I strongly urge you to contact that moderator - or an admin, or post in the feedback & questions forum. Making offhand comments about it in semi-related threads won't get you far. I mean this as a positive suggestion to help you resolve your issue, I have no involvement in the moderation of these forums.

James, you're handy - have you thought about DIY'ing your own drivers from scratch? Check the photo I posted in Soundwave's LED thread a minute ago - the DIY driver I'm using is based on the NCP3065 chip from On Semi, and took about 20 minutes to put together. Cost was maybe $5, and it has more functionality than any similar commercial driver.
 

james3370

Premium Member
i have considered it....like some of the DIY ones listed in evil's thread on nanoreef

i'd like to save some cash if i can seeing as the buckpucks are kinda pricey driver for no more than i plan on doing w/ them (the moonlights & fuge lights portion at least)

my biggest problem is figuring out exactly what i need....i can't read schematics for shat & am a functiong retard as far as the terminology LOL....but somebody shows me what to get & describes how to assemple it & i'm great. even if it's giving me the formula(s) to figure out resistor values & such i can do since i am good at math
:rollface:
 
For the moonlight LEDs you could even just do an LM317-based driver - it'll operate in constant current mode with only two or three external parts. Total cost $2 or so. Not incredibly efficient but you'll be running at pretty low power levels anyways, so no big deal.
 

stugray

Premium Member
james3370,

"the only way i can come up w/ to do like i'd like to do is this:
* 350ma dimmable buckpuck>>blue leds
* 700ma non-dimmable buckpuck>>white leds"

How about putting two 350ma Blues in parallel in place of one 700ma white that you have?

They wont balance perfectly and are susceptible to the "parallel meltdown" that we discussed before, but if one blue blows, you will only lose two Blues.....

Stu
 
<a href=showthread.php?s=&postid=15421284#post15421284 target=_blank>Originally posted</a> by stugray
james3370,

"the only way i can come up w/ to do like i'd like to do is this:
* 350ma dimmable buckpuck>>blue leds
* 700ma non-dimmable buckpuck>>white leds"

How about putting two 350ma Blues in parallel in place of one 700ma white that you have?

They wont balance perfectly and are susceptible to the "parallel meltdown" that we discussed before, but if one blue blows, you will only lose two Blues.....

Stu

IMHO the problem with approaches like this is that it really limits controllability. The "steps" of control, assuming you are trying to drive blues and whites on the same driver and just using different parallel/serial schemes to cut power to the blues, are pretty large. If you nail a setup that gets the whites just right, but you want the blues a tiny hair dimmer, you might be stuck.

In contrast, putting each color of LED on it's own driver gives you perfect, independant control of brightness for each function.
 

james3370

Premium Member
<a href=showthread.php?s=&postid=15421283#post15421283 target=_blank>Originally posted</a> by der_wille_zur_macht
For the moonlight LEDs you could even just do an LM317-based driver - it'll operate in constant current mode with only two or three external parts. Total cost $2 or so. Not incredibly efficient but you'll be running at pretty low power levels anyways, so no big deal.

that's what i was thinking of trying....(3) & running them around 200ma w/ a 12v wall wart

wainting on kcress to explain the "shunting resistor" cause i like the idea of them all being on the same driver & wall wart if possible
 

james3370

Premium Member
i'm not too worried about the whites running at full power since they are just for the fuge....i just don't want to pull them down real dim like i want the blues to be

controllabilty isn't a concern either. once i get the level i want, it will stay that way.....not doing any kind of dimming, just want to have a few running as bright as possible (fuge) & a few running at a much lower intensity (moonlights)
 

james3370

Premium Member
before i make it harder than it has to be, i might just try using the lighting film insane mentioned. this gets them all on the same driver (might DIY my own or possible a std 700ma buckpuck) & 1 wall wart.

i'm thinking (5) leds total...3 blues & 2 whites...ran at 700ma. they have a forward voltage of 3.5 so thats 17.5v & i have a 20v/1a wall wart to drive them. then just put the blue film over the blue moonlights to cut the intensity some
 

kcress

New member
Hi James!

You know, I am the champion of "don't parallel", but in small setups where the amount of money hanging out is minimal, it can make sense.

You can run two blues in parallel in place of a single blue. You just add a very small "load sharing" resistor in series with each of the two in parallel. The small value resistors act to balance any dissimilarities in conduction that the LEDs have. A 1/2 ohm resistor with a 1/2W rating would do the trick, even a 1/4 or 1/10th ohm would work well too.

You would have both diodes connected on one side(same polarity).

Then the other sides would each have the above resistor attached to them.

Then the other end of the two resistors would be connected together.

This "pair" would be dropped into the LED string like one LED. Each LED would have half of the string current flowing thru it.


If you want to actually do the shunt thing, keep in mind that you are wasting every drop of the power being shunted which wouldn't happen in the above case.

But to continue:
To shunt a LED for dimming you solder a resistor from the plus to minus terminals on any particular LED in your string that you want to reduce current thru.

If your LED has a forward voltage of 3.5V with 350mA supplied to it you want to choose a resistor that would pass about 350mA at that same 3.5V The ultimate current you desire thru that LED is 350mA so try to look up or estimate the forward voltage across the LED at that current. The chosen resistor also has to be able to dump all the waste heat that it will be turning the shunted current into.

3.5V/350mA = 10 ohms.

Watt rating = 0.35 x 0.35 x 10
Watt rating = 1.3W

This means you would want to use a resistor of 2W rating or higher so it doesn't run so hot as to fry your fingers or de-solder itself.

You can go with any type and the more wattage the better.
 
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