kcress's Turf Scrubber build.

[kcress]

Greetings!
I'm finally getting my act slowly together.

I'm building a TS that is entirely LED based.

I started initially building a variant of SM's 3G. There are so many technical issues with that style design that it rapidly became unwieldy. The biggest single issue is getting electrical power into the screen itself and then having this connection require a connect/disconnect plug that wouldn't get contaminated in handling and washing the lit-screen once a week. That is a real problem. Also any LEDs used have no opportunity to expand their light patterns. You need about an 1-1/2" for 30 degree LEDs to expand to a reasonable spot size.

My design is two fairly dense walls of LEDs I've selected, out of hundreds, for their brightness and wavelength. Each wall will have 132 alternating red and blue LEDs pointed inward at the central two sided screen. They will be spaced such that their light spots will mix at about 50/50.

The screen will be hung in the center. It has a handle to remove it like a cartridge. The entire unit will be made of acrylic. The screen itself is a 1/4" acrylic sheet. To provide grip for the turf there are over 200 slots routed in each face. These slots should provide a hold for the turf preventing complete removal during a cleaning.





Here's the screen:

[SantaMonica]

Looks like a great start! You should be able to get the LED's to within a 1/2" of the screen (although this might not be needed.)

These slots should provide a hold for the turf preventing complete removal during a cleaning.

They will certainly help, but still rough/scratch it up a lot. And you may still want to consider epoxying a screen onto it, depending on how well the holes work.

As for the previous G3 concerns:

The biggest single issue is getting electrical power into the screen itself and then having this connection require a connect/disconnect plug that wouldn't get contaminated in handling and washing the lit-screen once a week. That is a real problem.

One way I though of dealing with this is having the power come in from a permanent wire from the top. The wire would exit out of the water, to a connector that would be in dry air. The connector would thus be unplugged first, and then the screen would be free to be lifted out.

Also any LEDs used have no opportunity to expand their light patterns. You need about an 1-1/2" for 30 degree LEDs to expand to a reasonable spot size.

The LEDs I was looking at were either 90 or 120 degree ones. And with a diffuser/prism sheet on top of them, it should (have not tried it) be totally spread out.

[kcress]

Thanks SM.

Here's the next part. This is one of the two LED walls.

[SantaMonica]

What's the horizontal slots for?

How far will the LEDs be from the screen? Will you be diffusing/prisming them?

[kcress]

Been a change in plan. (Proto-types.. sheesh.)

The slots are/were for wiring the LED connections. The routed holes for the LEDs are all made horribly opaque by the machining process and there is no good way to return transparency. This opacity is blocking 50% of the LED's light.

I am mulling several alternatives. This panel was the inner wall and the LED panel all in one. This required at least 1/4" acrylic. Now I will replace this with a thinner inner face since it just needs to be waterproof. I will make a box on the back of this thin face that will hold the LED structure, (now just dropped in), and then backed with a glued on smoked rear cover to reduce light leakage.

The LED structure needed to hold them all in position will be either an engineering plastic or acrylic sheet machined to hold the LED leads for manual soldering or I will use a single sided sheet of copper cad laminate which I will route to hold each of the LEDs that can then be machine soldered in a conventional manner. This then will be dropped into the "acrylic box".

I'm checking on the price of the copper clad verses the labor/cost of an acrylic/engineeriing plastic design.


The LEDs will be about 2 inches from each face of the screen. The LEDs are about one inch apart in alternating colors. The spots they cast at 1-1/2" theoretically overlap about 95%. So the same blue and red mixture should uniformly cover the screen even if it grows out 1/2" from the face of the screen. My calculations show I need no diffusion or prismatic assist. But! If I do this new design change would make that very simple as I can drop the diffuser into the aforementioned "box" before the LED panel goes in. Everything added, of course, costs more $$ and every surface in between the LEDs and the turf reduces the photon energy at the turf by at least 5% so I would rather not add anything unless my theory is bad.

Thanks for the thoughts.

[SantaMonica]

This opacity is blocking 50% of the LED's light.

Maybe not. Maybe it's just diffusing greatly. After all the material (acrylic) has not changed. Even if melted, it does not become opaque; it just diffuses, as if you sanded it. It may actually be what you want.

As another alternative, how about reversing the LEDs so the leads go through the acrylic, but the lens shines out the open hole?

the same blue and red mixture should uniformly cover the screen even if it grows out 1/2" from the face of the screen

Remember that most grow lights use much more red than blue, I think about 5 to 1.

every surface in between the LEDs and the turf reduces the photon energy at the turf by at least 5% so I would rather not add anything unless my theory is bad.

If so it's another chance to design a G3 (with power out the top)

[diy]

I am mulling several alternatives. This panel was the inner wall and the LED panel all in one. This required at least 1/4" acrylic.

This is exactly what I working on doing right now. But I am using 110 superflux LEDs mounted on a standard circuit board. I made a mold 12x12" out of wood (making sure all corners are perfectly square. Sit the circuit board in the mold and pour a ultra clear poly resin in covering everything except the LED lens. Superflux LEDs are 1w high power 5mm LEDs, They are perfect for a application when you need the light source to be extremely close. They also have 120 degree viewing angle and they emit little to no heat. Also with all the searching I have done, I figured out ALGEA loves red more than any other color. I would do a 8:1 ratio.

Heres my layout. Good luck with you scrubber

[kcress]

SM; The opacity is blocking the light. If you hold up a white piece of paper 1-1/2 inches from the front, the light from this verses just holding he LED behind the clear acrylic is huge.

I want this LED panel really close I can't see how to use one in five blue and have it actually work. Not enough spreading distance. These red ones are very bright so I hope they'll be enough even 'diluted' by 50% blue.

The G3.. Think of plugging and unplugging some connector 60 times a year. Then having it flop around as you scrub the screens - water getting in it. Most connectors, (that never have salt and water splashed on them), are rated for about 100~200 plug in cycles. More than that and they start to fail.


diy; Aren't those 'superflux' LEDs four LEDs in series already? How can you put 8 of them in series and then still drive them with only 24V?

Hope you can shoot us a picture!

[SantaMonica]

I would imagine that waterproof marine connectors would be cheap and easy to find. It's only 12V or so, and hardly any current. Or, maybe there could be no connector at all, and the power just runs all the way to the supply. The user just needs to know to install it with enough free-length so he can get it to the sink.

By the way, shouldn't every setup be using an isolation transformer to prevent a possible short to 120V?

[diy]

diy; Aren't those 'superflux' LEDs four LEDs in series already? How can you put 8 of them in series and then still drive them with only 24V?

Hope you can shoot us a picture!

There will 13 strings of 8 LEDs in series. Then the strings will be connected in parallel, So far we are at 16 volts. Then I will run 2 strings of six LEDs in parallel. This puts me at 22volts. The illustration was done in the early design stage and I haven't bothered to change the schematic but, you get the idea, right?

I'll be sure to post a pic when Im finished. I just ordered everything so give me two weeks. Good luck with yours