diy led lighting

arscott82

I just got done reading This deserves another journal...My 190g Wild Discus build! [Archive] - MonsterFishKeepers.com and he has an amazing light set up. I have read here that led does work with plants (Geomancer). I was wondering if anyone has tried to build a light set up kinda like this. I really like the idea of slowly bringing the lights to full power and slowly turning it off. As to not shock the fish with instant on and off. I'm not dumb with electronics as I am an electrician, but I've never dealt with programable electronics that much. I think I'm going to keep researching and try and build a fixture myself. Just wanted to know if anyone here had some ideas on how to do it and some good places to buy the parts.

Geomancer

I didn't read that other thread, but to answer your question on how you do a dimmer with LEDs, it is done with pulse width modulating (PWM) them.

For automated control, they probably use a microcontroller and a real time clock (to get time of day information).

A microcontroller will usual handle PWM by using a counter. Every clock cycle it will 'count' and compare the value to a threshold value. If it passes the threshold, it turns the LED off and continues to count. When the counter rolls over back to zero, it turns the LED back on.

By changing the threshold, you change how long the LED is on during a time period. The longer it is on, the brighter it will be because it approaches the point where it is constantly on anyways. The shorter the pulse, the dimmer.

Without knowledge of assembly or C, programming a microcontroller will be quite a challenge, but not impossible.

To go further with an RGB LED you can use this method to generate every possible color (well, lots of colors anyways). An RGB LED has three LEDs in it; red, green, blue. As we all know, from those primary colors you can make any other color. So by using PWM on each LED individually you can change how 'bright' each color is and thus the overall color. This isn't useful in an aquarium though ;)

EDIT: I edited my original post to provide more information on the implementation of a dimmer with a microcontroller.

Geomancer

I went ahead and read the second on lighting in that post. I was pretty much spot on


However, before you get your hopes up you'll need to set your budget.

That setup probably cost that guy several hundred bucks, just on lighting alone. To get a custom PCB made you're looking at ~$100 alone for a double sided board. An aluminum heatsink the size of that light fixture had to cost a fortune. Thick, clear acrylic for his splash guard isn't cheap either. Even a power supply like that is pricy. The microcontroller is a development board that's pre-made and mass produced so not too bad at about $22.

I'm cheap, so I cut corners which you can see in my not-so-pretty fixture I made But I only spent $50-$60 total on it too.

arscott82

Yes, I don't really have knowledge in these.

This is for my future tank I plan on getting. It's not nearly the size he has. I just want a 40 gallon breeder tank, so hopefully I can save money with a smaller fixture. My budget will probably be around 2 to 300. Plus I have a while until I get my tank and set everything up so I'm hoping to start piecing this together slowly to help the budget. The rgb leds would be cool, but can't I just get some 6500k and some 5000k leds and hook them up every other one?

If I was to start on this soon, what do you think would be the first step?

Geomancer

Yes, you would want to get LED's with a color spectrum between 5000-7000K for plants. Mine are 5665K which were significantly cheaper than the 6500K ones they had. I was just talking about RGB LEDs as an example of what PWM can do, they would not work in an aquarium.

The size of the tank to the cost is somewhat irrelevant. Yes you will have fewer LEDs which is less cost there, but you still need all that other stuff to go with it (micro controller, power supply, constant current source, etc) and all that will be roughly the same price as he paid. For mine I used individual heat sinks for each LED, versus a single large one that's really overkill, but his fixture looks far better than mine aesthetically.

You have two starting points, the LED fixture or the microcontroller.

Honestly, I'd probably do the LED fixture because if you aren't able to get the microcontroller working you can just use a regular mechanical switch in its place for on/off control of the lights.

For the constant current source, that will also be a difficult task as you'll need a custom PCB which you'll have to design. Since this isn't your area of expertise, you may want to just look for pre-made modules. They'll be more expensive, but removes all that risk. They're as easy to wire up as a fluorescent ballast pretty much.

arscott82

So should I look into buying an already built led fixture or is that something I should make? Lets say I can find a 3 foot led fixture, can I take the leds out and put the new ones in and retro fit that fixture? Or would it be better to have one made. I have a good friend that is a sheet metal worker and he could make one out of sheet metal really cheap for me.

Geomancer

You can't retrofit an existing one, not unless the new LEDs have the exact same current and voltage requirements.

The modules I was talking about were constant current modules. Here are quite a few, you would need to get one that matches the LEDs.

Power Supplies - External/Internal (Off-Board) | LED Drivers - Constant Current | DigiKey

You can use pre-made LED modules paired with a constant current module to be 90% there.

VLPC1201A2 Vishay Semiconductors | VLPC1201A2-ND | DigiKey

You pay for the convience of having it built for you though.

arscott82

For the retro fit, I was thinking more like just gutting the whole thing and just using the shell for the looks of a bought fixture. But after looking at those two sites I can see this is going to take some time and reading because I don't have a clue in what I'm getting into. Just thought I had to buy a couple pieces and wire them together and bam I have my fixture. I still want to do this and am going to, but it's just going to take some time.