LED lighting system... - Page 2

BeanAnimal · #26 09/08/2007, 10:44 PM

Series LEDs drop voltage, current remains constant

nynex · #27 09/08/2007, 10:55 PM

First off 5mm are too small for anything but moonlights.
I have 5mm LED arrays on all my tanks for moonlights and they work great, but
for a main light source they dont work..

I know someone who made one for their 3 gal and used 50 5mm leds with no
resistors...It worked for his 3 gal. He knows alot about this stuff, but he said
when he made the array he was still learning and got lucky on the no resistors
part, cause he was seriously over driving the LED's. It actually still works fine, he
told me.

But I used 10mm 145,000mcd super bright LEDs for mine, with 3 in a series and
4 series in each group. 36 LEDs total Half White andf Half Actinic Blue. I also used
9 Wide Angle Actinic LEDs for the moonlights. This was an array for my 3 gal Nano.
I put 1 resistor at the end of each series and the brightness was not good at all. So
then I tried it with no resistors and it was awesome!..for about 5 mins before I
blew out half the array. So now ive rebuilt the array and with the help of the
person who built the 50 led array...we figured to push the LEDs to the max
without blowing them out. I would need 12 volt 6ohm resistors. Ive also tried a
varied range of power supplys...12 volt 1.5 amp, 500ma and 800ma. I think with
the 500ma and 12 volt 6 ohm reisitors, it should push the LEDs to the max 3.8
volt without blowing them out.But im not holding my breath...Im losing faith in
this project.

I will pick up the 6 ohm resistors this week and see if they make any difference.

Here is a pic of thr array partially rebuilt.

BeanAnimal · #28 09/08/2007, 11:47 PM

This is why current source drivers are so nice. You do not need to mess with resistors

Check out the phidgets LED64 It needs to be hooked to a USB port, but it s cheap and adaptable driver that can be controlled with simple code.

National, Dallas, and others make LED driver chips. Browse through a few datasheets and you will be amazed at what some of them can do with very few parts.

speakerguy · #29 09/09/2007, 12:03 AM

Even a simple LM317 or other adjustable regulator can be turned into a current source. You lose adjustability with that setup, but it'll cost you all of $1 in parts to get up to 1.5 amps of current. You would of course need some kind of power supply to feed it.

BeanAnimal · #30 09/09/2007, 12:20 AM

BeanAnimal · #31 09/09/2007, 12:34 AM

Sorry for the large dimensions. The appliation was designed to run on an 800x600 touchscreen. That is the scheduling page.

What bearing it has on this thread... well I dunno. I mentioned the software, so I figured I would post a screenshot.

liveforphysics · #32 09/09/2007, 07:20 AM

I mentioned it earlier in the thread here, but I've dont lots of work with driving LEDs, and useing high power LEDs.

Nobody uses voltage for power control. Nobody uses resistors.

You run chains in series, and you use current control to drive them. The methods used in these circut board layouts is not only silly, but the temperature effects on the voltage needs of the LEDs to supply idea current can not be optimized.

The function the LED cares only about current. Current is what output varies directly with. The voltage it requires to draw the current it wants is a property of a bunch of factors, and it varies in a pretty large way from LED to LED unless you are buying from selected bins.

The LED array that was offered to you was genius. If those are Lux3's or K2's, you would need around 400 5mm superbright LEDs to equal the output.

I would definately considder a revision to use controlled current and series chains. It also happens to be easier to make

Best Wishes,
-Luke

BTW- Bean, cool software!

BeanAnimal · #33 09/09/2007, 08:23 AM

My first venture into VB.NET and threaded applications. I used a threaded scheduler module I found somewhere and hacked the guts out of it to do what it does. Stability testing right now

MarkS · #34 09/09/2007, 08:32 AM

OK, this will be controlled with a microcontroller. If what you guys are saying will work with the PWM output from a microcontroller AND if it will still allow me to daisy chain multiple boards together, then I'll use your method. However, YOU HAVE GOT TO BE MORE SPECIFIC! I am not an engineer, just a hobbyist, so please quit talking in circles around me.

BeanAnimal · #35 09/09/2007, 10:07 AM

Mark most of the dedicated drivers do their own PWM. You just provide a digital signal to set the level.

BeanAnimal · #36 09/09/2007, 10:13 AM

http://www.linear.com/pc/viewCategor...C1,C1003,C1094

Boost: (3V supply)
http://www.linear.com/pc/productDeta...4,C1766,P37356

Buck: (12V supply, etc)
http://www.linear.com/pc/productDeta...4,C1768,P37747

National and Maxim also make some products that fit what you are look for:

BeanAnimal · #37 09/09/2007, 10:15 AM

http://www.national.com/appinfo/power/led.html

http://www.arduino.cc/en/Tutorial/LEDDriver

http://www.allegromicro.com/en/Produ.../leddriver.asp

http://www.onsemi.com/PowerSolutions...rics.do?id=197

http://focus.ti.com/paramsearch/docs...ODE_STRY_PGE_T

TIMMYE · #38 09/09/2007, 02:21 PM

And I thought I had a good understanding of how to do DIY led stuff.....well not anymore thanks guys!

MarkS · #39 09/09/2007, 03:51 PM

I was looking at this chip when I originally designed this system, but disregarded i: http://www.parallax.com/detail.asp?product_id=603-00001

It looks like it might do exactly what I want.

BeanAnimal · #40 09/09/2007, 04:46 PM

I would not pay $20 for it!

www.findchips.com

MarkS · #41 09/09/2007, 05:34 PM

I didn't even see the price!

Jameco - $8.95

Digi-Key - $5.43

speakerguy · #42 09/09/2007, 05:41 PM

You have to buy 2,505 of them to get the Digikey price.

BeanAnimal · #43 09/09/2007, 06:00 PM

Yeah single lot quantities go for around $11

So plan your oder around other needed items and save some money

original kuhli · #44 09/09/2007, 08:15 PM

Quote:

AND I just found out that Parallax' PING can be used to read water levels. Hmm... An ultrasonic evaporation control system would be REAL easy.

That's what I'm looking for but I'm a newbie to electronics...can you elaborate on how one would set one up? I'm using an Aquacontroller jr though...

original kuhli · #45 09/09/2007, 08:17 PM

Quote:

AND I just found out that Parallax' PING can be used to read water levels. Hmm... An ultrasonic evaporation control system would be REAL easy.

That's what I'm looking for but I'm a newbie to electronics...can you elaborate on how one would set one up(the sensor/chip arrangement)? I'm using an Aquacontroller jr though...

MarkS · #46 09/09/2007, 08:39 PM

The PING))) sensor emits an ultrasonic pulse and then listens for its echo. From this it can calculate the distance to an object in front of it. Its used in robotics applications for obstacle avoidance. It can accurately measure distances between 1" and 10'.

The engineers over at Parallax were getting quite a few questions about whether it could detect the distance between itself and a body of water. They did some testing, here, and found that it could accurately determine the distance to the water's surface up to 10' away.

This is not a hard project to do for an electronics project, if you have some programming and hardware experience. However, if you don't it will all be Greek to you. I'm not going to discourage you, but you'll need to do quite a bit of research first. What I'd recommend you do, if you're serious about this, is buy Parallax' Board of Education (BOE) and the PING sensor. The BOE comes with a very detailed manual with tons of projects and assumes that you know little to nothing about hardware design and programming. Its used in schools as a teaching aid. Personally, I'd spend a few dollars more and buy the BOE-bot kit. Its a really cool little robot with a removable BOE on top.

You will not be able to interface it with your Aquacontroller though.