DIY LED driver for reef lighting

[stephenrwright]

Does anyone look at the Luxeon LED from philips?

http://www.philipslumileds.com/products/luxeonrebel

Those are the ones I am looking at, I got 10 white and 10 royal blue to play with. I had to use a toaster oven to solder the first two to the star board, the metal core board sucked too much heat from the iron. Waiting on some solder paste to do the rest, but the regular solder worked OK on the first two. The CAT4101 board was not too hard by hand, even with the 805 resistor and caps, but I do have old eyes so I use a stereo microscope so I can see what I am doing. I should get the power supplies soon so I can test out a string of them. If I ever get it all together I will post some results.


Star board

White LED

Blue LED

Steve

 

[der_wille_zur_macht]

DER,

Did you account for the 4 terminal block on the dual board?

It was not listed in the BOM so I was checking as I am ordering the boards tonight or tomorrow. Not that it has any bearing, just wanted to know.

I also have to get two parts from mouser that digikey did not have in stock so I may was well pick up a few of these too.

Also any one got a picture of the dual board after assembly? For us new to electronics, the visual is always helpful.

I shoulda been more clear above - the 3.5mm screw terminals is what i used on the 3 x CAT4101 prototype I'm working on now. For the NCP3066 dual driver board, I put a single header with all the ins/outs on it, and it's .1" spacing. On the prototypes of that I built, I just used a male pin header. A 3.5mm screw terminal would have been too big to easily fit on that thing.

I don't think I have any photos of the NCP3066 dual driver but I can get one tomorrow.

 

[MuckTown]

Printed Boards

Printed Boards

Hey Der, I would like to get some of the printed boards for the CAT4101 design. I don't know how to get them printed. How are you getting yours done for the prototype?

 

[der_wille_zur_macht]

A few people have PM'd me so I'll explain here:

To get PCBs made, you need to get your hands on gerber files for the board (I put them up for the dual driver NCP3066 project, I will put them up for my CAT4101 design when it's tested). Then, you need to send the gerbers to a board house, who will make the boards and send them to you. (You can do them at home if you've got the equipment, but I'm not that advanced )

I used seeedstudio.com. Their webstore is:

http://www.seeedstudio.com/depot/

Click on open source service in the left menu, then prototyping service. They JUST changed their pricing structure - it's actually simpler now. When I ordered my boards as noted above, it was under the old structure. But here's how the new structure works: you place an order for the board size you want, then email them the gerbers. They make the boards and ship them to you.

They have two tiers in the service, based on board size. With a 5 cm * 5 cm max, it's $20 for 10 boards. With a 10 cm * 10 cm max, it's $40 for 10 boards. That's DIRT CHEAP and you likely wouldn't get a price that low from any other board house unless you were ordering quantities much greater than any of us will likely need. For reference, the CAT4101 and NCP3066 drivers I've designed are 5 cm * 5 cm, so it fits in the cheaper tier, and works out to 8 cents per square cm! For comparison, the next cheapest service I've found is the $99 special from golden phoenix (http://www.goldphoenixpcb.biz/). It's 1000 square cm for $99, which is basically 10 cents per square cm.

There are a couple options when you order, but you can pretty much ignore them (unless you want to spend a lot on different colored soldermask I guess.)

 

[TheFishMan65]

This forum is NOT for selling.~dc

 

[TheFishMan65]

dwzm,

I like gold phoenix (at least for my design). I was looking at PCB FAB Express. Cheaper for the five boards I need, but for a little more I get 10 (or 15) at GP. Decisions decisions? I was looking at around $16 dollars for my board. If I go with 15 that will get cut in half.

Thanks for the information.

Speaking of pricing check out FutureElectroncs. I will post a spreadsheet after I get some final number. For my board it looks like the prices will be about Future $40, mouser $45, and digikey $55. I tired to find the lowest appropriate device - so maybe you could go cheaper.

 

[der_wille_zur_macht]

I forgot to upload the link with the prices from the different venders.

If you haven't ordered boards or parts yet, I'd think about finding a different package for the parts you have in 0603 SMT. IME that's too small to solder by hand. Think of it this way - I posted a picture of some 1206 parts a page back:

FOUR of your 0603 parts would fit on top of ONE of these, and these are already pretty tiny! 0603 is like a spec of dust! Fine for a robot, but tough for a human.

 

[TheFishMan65]

We use them all the time at the office. Awkward yes, but I think I can handle it. If not I have a friend here that can do it. Time will tell

 

[der_wille_zur_macht]

Maybe I've got shaky hands and weak glasses.

 

[TheFishMan65]

I have not done it yet, but they may solder under one of those table mounted magnifying lamps. How many cups of coffee have you had today.:lol:

 

[cptbjorn]

What's the dimming performance on these?

I've used LM3404s for several LED arrays now and with an arduino they will dim XR-E crees down low enough to be used as moonlights. If these can do the same I might try a couple.

 

[TheFishMan65]

I assume you are talking CAT4101 is can go as low as 1%. Not sure what it takes to do moonlights, but it is my plan to try it.

If you start with lower than full power then it should definetly work. What I am not sure of is at 1A of current is a 1% on cycle still to bright for moonlights.

 

[Doolin]

I'll admit I haven't read this whole thread, but has anyone tried this?

 

[der_wille_zur_macht]

I'll admit I haven't read this whole thread, but has anyone tried this?

Yes. It was a fun experiment but IMHO is not ideal (for my needs at least).

It's terribly inefficient, unless you carefully match PS to your LED string. Even then, there's a TON of dropout, which means mediocre efficiency at best. It allows for no dimming control. The margin of error (for an LM317) is pretty big.

Plus, that circuit isn't really significantly cheaper or easier to assemble than a CAT4101, which has better accuracy and allows for dimming. Also, the CAT4101's minimum dropout is lower, which means it can be more efficient.

 

[Doolin]

I just read the datasheet on the CAT4101, those seem ideal. Good find DWZM

 

[der_wille_zur_macht]

I didn't find them, technically. I passed over them originally (last summer) because they were SMT-only, and linear, which didn't meet my criteria at that point in time. Recently, SpacedCowboy mentioned them again, which led me to re-evaluate them and realize they're easy to use and cheap!

 

[Doolin]

Ah, well done to whoever then!

 

[marspeed]

Question
if you were not using PWM to dim the LEDs what other methods or circuit would be required to accomplish dimming with the 4101

Marc

 

[TheFishMan65]

The 4101 also supports dimming through the sense resistor. So you have three options (that I know of)
1) change the resistor every time you want to dim or brighten - no really feasible
2) add a 10k potentiometer in series with the resistor - this is what I did
3) use an IIC 10k potentiometer - I thought about this, but decided not to
all of these can be used in conjunction with the PWM

 

[der_wille_zur_macht]

Or, a simple conversion circuit to generate a PWM signal from whatever source you have. What would you have available to control the drivers?