In-Hood LED Retrofit - The Planted Tank Forum
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post #1 of 25 (permalink) Old 05-31-2014, 03:19 PM Thread Starter
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In-Hood LED Retrofit

Hi Guys,

I'm new here and looking for advise on replacing the two 24" tubes in my tank with LEDs of some description. The tank is approx. 32"W x 18"H x 14"D (depth being front to back in this case).

I see here that most people prefer hanging lights high above the water. Unfortunately thats not an option for me due to the tanks intended location in the new house we are moving to. The LEDs will have to go where the original tubes were in the plastic tank hood.

I'm planning on getting some long 2" wide heatsink strips (probably gratis through a supplier at work) and adding a selection of cool white, red and blue LEDs. Probably Chinese jobs from our favorite online bazzar. All Happily controlled by an Arduino controller.

What I'm struggling with is which LEDs to use, how many channels to put them in, and where to get a suitable MOSFET driver board from cheaply.

SO does anyone have any advice, links etc for a beginner in all of this.

Cheers

Chris
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post #2 of 25 (permalink) Old 05-31-2014, 05:00 PM
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The easiest way to make a LED light is to use the tapes of SMD LEDs, preferably 5630 size. See https://www.plantedtank.net/forums/sh...113&highlight= for how I made mine. One of the big advantages of these is that all it takes to power them is a 12 volt DC supply, with adequate current capability. One of the big disadvantages is that you can't easily get deep red or cyan LEDs in this format. But, it is worth considering before you go for individual LEDs.

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post #3 of 25 (permalink) Old 05-31-2014, 05:45 PM
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I did almost exactly what you're describing about 3 years ago.

Bought some CREE LEDs, mounted them to a DIY heat sink in my hood. Ran them off a TIP120 power transistor powered and regulated via an Arduino.

I really like my finished product, but it took A LOT of hours to put it all together and get it to work.

5630 SMD LED strips are the way to go. So much easier than individual high power LEDs. The heat management, wiring, and mounting is all 10X easier than buying individual 3W LEDs like I did.

You'll save a few bucks with an Arduino, but the only real reason to use one is if you like tinkering with them. Otherwise IMO its just a time sink that you'll get frustrated with, when you could have just used an off the shelf plug and play controller that would have only cost an extra $20.
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post #4 of 25 (permalink) Old 05-31-2014, 07:38 PM Thread Starter
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That's just it. What I really need is to indulge my inner geek!

I'm fixed an an arduino controller, with fade in and out, possibly linked to the time of year. And also some kind of moonlight, again probably on a 2 weekly wax and wane.

So assuming I go with the 5630s that makes the install in the hood really easy. What I want is an easily available board populated with mosfets to allow me to control then. Any ideas?

Also what colours? Cool white for the bulk of them, plus a few warms, then would you bother with a strong of red and blue 5050s?

Or even a couple of RGB 5050 strips allowing for the moonlight stuff?

So many questions!

Thanks

Chris

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post #5 of 25 (permalink) Old 05-31-2014, 11:23 PM
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Right on! You remind me of myself

You don't need many moon lights (blue). A couple of watts worth of them will give a pretty good illumination at night. I think I have 1.5 watts worth of them on a 50 gallon tank and its plenty IMO.

I would focus mostly on COOL WHITE (6500K) LEDs. I would maybe do 1/3 warm white, and 2/3 cool white. My understanding is that plants do best with cool white(~6500K), any other colors you add are really just for aesthetics.

Make sure whatever LED strips you get that you add up the wattage to figure out how much you need.

I have my warm LEDs fade on in the morning (to simulate sunrise) and then fade out around noon time, with the Warm white LEDs fading in around 8 am, then being on %100 during midday. So the tank is a yellowish white in the morning and fades to blueish white at midday, then fades yellowish white in the evening, which is pretty close to sunlight. Not hard to do with an Arduino, and I think its a really cool effect.

I could go on for paragraphs telling about how I programmed and wired the Arduino to get it to work well.

You'll want a REAL TIME CLOCK module to hook up to the arduino, otherwise you'll have a hard time keeping the time correct.

I don't know of a ready made mosfet board that you can use to fade the LEDs. I used TIP 120 transistors to power the LEDs. I don't know if thats the BEST method, but it worked for me. Its a little different, because they operate off the negative leg of the power. And its really easy, only a handful of components.

I don't know what your electronics background is, but I have an Electrical Engineering degree, so I'll get pretty technical here. I can explain things more simply if you want, but if you're going the Arduino route, you'll have to know basic electronics to get everything to work.

Here's a rough diagram I drew up of how I wired up the LEDs:




The PWM output of the arduino powers the TIP120. I put a 2000uf capacitor on this leg which makes all the transitions SMOOTH as butter. If I didn't add the capacitor, then I could distinctly see the LEDs light up in "steps" of intensity, and I really disliked it. The capacitor makes it a pain in the butt to program, but the finished result is much better.

I don't know what size resistor you'll need. The way my code is written it doesn't really matter, because the arduino kind of calibrates its output depending on current readings. Depending on the voltage/current of your LEDs, you'll probably need a 4.7K-30K resistor. Something in that range.

LED ouput is mostly a function of amps, not volts, and they typically ramp up really quickly when you approach their operating voltage. For instance, they might be 10% power at 11.1 volts, 50% power at 11.5 volts, 70% at 11.8V, 90% at 12.1 volts, and 100% at 12.2 volts, but if you measure the current, you can tell exactly what power level they're running at, instead of depending on a narrow range of voltage to monitor their output.

To measure the current, I put a 1W 1 ohm resistor on the incoming power. This makes it easy, because the number of milivolts accross the resistor is the number of miliamps. For instance: 20mv at the resistor means there are 20ma of amps going to the LEDs.

Anyway, that's enough rambling for now. I'm sure there are easier ways to do it, but the method I used I think is about the cheapest way to do it, and it made a good end result for me with very few (and easy to get) parts.
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post #6 of 25 (permalink) Old 05-31-2014, 11:48 PM
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I found a board on Ebay that might work:

16 channel 12 Bit PWM I2C FET Arduino schield PCA9685

If you break your LEDs into 1 amp segments, this could be a relatively easy way to control them.

And it has the added bonus that its PWM output has 12-bit resolution (4096 steps), while an Arduino (unless you do some tricky programming) only has 8 bit resolution (256 steps).

The trick is that these chinese boards have almost no documentation, so it can be hard to get them to work properly.
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post #7 of 25 (permalink) Old 06-01-2014, 02:39 PM Thread Starter
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i2C is a bit of a mystery to me to be honest! I think I will steer clear for now.

What about this

hmm ebay link removed.See item 400709527586

I have asked for a circuit diagram. lets see what happens

CHris
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post #8 of 25 (permalink) Old 06-01-2014, 03:16 PM
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Quote:
Originally Posted by chrislewis View Post
i2C is a bit of a mystery to me to be honest! I think I will steer clear for now.

What about this

hmm ebay link removed.See item 400709527586

I have asked for a circuit diagram. lets see what happens

CHris
I think there's a typo in that item number. Ebay says there is no such thing.

Hoppy
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post #9 of 25 (permalink) Old 06-01-2014, 03:20 PM Thread Starter
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400709527586 works on the .co.uk ebay site , not sure if that makes any difference!

Anyway search for
Four Channel 4 Route MOSFET Button IRF540 MOSFET Switch Module For Arduino

Chris
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post #10 of 25 (permalink) Old 06-01-2014, 03:40 PM
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Quote:
Originally Posted by chrislewis View Post
i2C is a bit of a mystery to me to be honest! I think I will steer clear for now.

What about this

hmm ebay link removed.See item 400709527586

I have asked for a circuit diagram. lets see what happens

CHris
Good find! I2C is pretty easy, its a basic communication protocol that the majority of arduino expansion boards use, but it can be a pain in the butt in an aquarium environment since there's a lot of noise (ask me how I know )

That board should work really well for you.
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post #11 of 25 (permalink) Old 06-01-2014, 04:39 PM Thread Starter
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I'm aware of i2c just not very familiar with it. For now 256 levels of dimming is fine (assuming the LEDs run at the lowest levels)

I'll probably go with the suggestion of 2/3 cool and 1/3 warm white 5630 waterproof strips.

Do you think it would be worth adding a couple of strips of red and blue (they only look to be available in the summer 5050 strips)

Chris

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post #12 of 25 (permalink) Old 06-01-2014, 06:52 PM
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if you're powering LED, you'll need a LED driver, not any old power supply. You can get a MeanWell, ldd driver http://www.ledgroupbuy.com/ldd-drivers/
You can connect your arduino's PWM to this driver.
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post #13 of 25 (permalink) Old 06-01-2014, 10:50 PM
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Quote:
Originally Posted by chrislewis View Post
So assuming I go with the 5630
There are plenty of off the shelf timers for strips..

Example :

http://www.alibaba.com/product-detai...175805058.html

you can reprogram via USB. Probably an Adruno clone "core"

Quote:
Programmable Timer/Dimmer

-Control up to 5 Channels
-Control up to 4 Channels independently
-Control up to 5 Devices(Leds,Fan,Power Head,Wave Maker, Etc..)
-Set Scenes by time and Intensity
-Program Timer(On/Off Time) & Dimmers to Increase/Decrease intensity from 0-100% over 24hr periods
-Create up to 50 Different Modes
-Create Up to 50 Different Scenes
-Create Modes/Scenes on the easy to use Computer Program(Provided) Download to Controller Via USB Cable(Provided)
-Control Time, Modes, Date, and Sounds,Via controller and LCD screen
-Perform Auto-run at 250X Speed to see created modes/scenes prior to setting
201039074252

for $50 it will get you through the months of getting an Adruno built,configured,programmed and hooked to your computer...
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post #14 of 25 (permalink) Old 06-03-2014, 12:11 PM
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Quote:
Originally Posted by mistergreen View Post
if you're powering LED, you'll need a LED driver, not any old power supply. You can get a MeanWell, ldd driver http://www.ledgroupbuy.com/ldd-drivers/
You can connect your arduino's PWM to this driver.
You can use a regular power supply IF you also monitor the current with your arduino, and use the arduino to adjust the output based on the current readings. Then your arduino acts as an LED driver, as all LED drivers are, are current regulated power supplies.

I will say with how cheap LED drivers are these days, there isn't really a good reason not to use them.
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post #15 of 25 (permalink) Old 06-03-2014, 12:30 PM
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Quote:
Originally Posted by PhysicsDude55 View Post
You can use a regular power supply IF you also monitor the current with your arduino, and use the arduino to adjust the output based on the current readings. Then your arduino acts as an LED driver, as all LED drivers are, are current regulated power supplies.

I will say with how cheap LED drivers are these days, there isn't really a good reason not to use them.
Are you not generally restricted to max 5V out and then all "small" LED's are in parallel... @ say 1A each, I'm not sure the Arduino would last long..

IF using an outside PS and all the resistors you'd need (though cheap) I don't see a practical (w/ my admittedly little knowledge and understanding of this "stuff") way of using "just" an Arduino...




but as you said.. at $7 each might as well throw an Menwell-LDD in between...
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