Re: another Brightness question

Andrew Stone

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Feb 21, 2012, 2:59:29 PM2/21/12

to Phil Spitler, toasted-circu...@googlegroups.com

With your 12v supply, you can probably even use 3 LEDs. Within the "high brightness" category you can't trust the LM values unless you know the manufacturer (i.e. Osram). Trust the mA rating and the cost (more efficient LEDs are more expensive). Manufacturer branded LEDs are rated a lot less bright (but still look awesome!!). In fact, for any "unbranded" LED, I'd strongly recommend running them a few mA lower then rated. Try 15mA for example instead of 20. This will keep them good for longer. But I'm not negative on unbranded; they cost so significantly less you can easily use 2-3 for the same price.

You are going to be *much* happier with the brightness of 3 LEDs in series then with one LED that is supposedly 3x as bright.

You can make a mold and pot 3 LEDs in epoxy to make a single "bulb". Check out "Cantin Craft" products for stuff that's easy to get and pretty good: http://www.michaels.com/on/demandware.store/Sites-Michaels-Site/default/Search-AdvancedSearch?cgid=entire&simplesearch=Search&q=castin+craft

Cheers!
Andrew

On Tue, Feb 21, 2012 at 2:08 PM, Phil Spitler <ph...@bonfirelabs.com> wrote:

Andrew, sorry to bug you once again but I have another question for you.

A while ago you said I can power 2 LEDs from each output, I'm thinking I might do this to give me extra brightness in each ball.

My question is, could I just buy brighter LEDs to keep my project neater or would 2 LEDs be a better way to go?

Here are the LEDs I am currently using, I am using the white LEDs. If I am looking for brighter LEDs would I be looking for a higher Luminous Flux/LM ?

Thanks again.

Phil

Phil Spitler | Associate Creative Director | Bonfire Labs | t : 415.394.8200 | c : 415.571.3139 | Bonfirelabs.com

Phil Spitler

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Feb 21, 2012, 3:01:22 PM2/21/12

to Andrew Stone, toasted-circu...@googlegroups.com

Thanks for the great info.

Phil

Phil Spitler

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Feb 21, 2012, 3:04:18 PM2/21/12

to Andrew Stone, toasted-circu...@googlegroups.com

Do I need tweak any of the onboard pots to power 70 x 3 LEDs?

And to clarify, they should be in series?

Thanks.

Phil

On Feb 21, 2012, at 11:59 AM, Andrew Stone wrote:

G. Andrew Stone

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Feb 21, 2012, 10:33:31 PM2/21/12

to toasted-circu...@googlegroups.com, Andrew Stone

yes, put them in series, and you'll need to turn up the center pot until the voltage it produces is just higher then the forward voltage of the LEDs in series. The easiest way to do this is to hook a few up and then turn the pot until they light up! Note don't go above 12v! You won't if you are using the 12v supply I resell... And you don't want to run lots of single LEDs and just a few triple LEDs...the extra voltage being delivered to the single LED will have to be burnt off by the M5451 chip as excessive heat.

Cheers!
Andrew

Phil Spitler

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Feb 21, 2012, 10:49:14 PM2/21/12

to toasted-circu...@googlegroups.com, Andrew Stone

Great, I'll try that later this evening.

Out of curiosity, what does the other 2 pots do (bri Left, bri right)?

Thanks.

Phil

G. Andrew Stone

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Feb 21, 2012, 11:57:34 PM2/21/12

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They adjust the current going through each LED (brightness) for the left and right IDE connectors.

Phil Spitler

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Feb 22, 2012, 12:05:15 AM2/22/12

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Great, thanks.

I just put 3 in series and tweaked the pot and they look good.

One last question, where do I measure the voltage in case I want to go back to having just single LEDs.

G. Andrew Stone

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Feb 22, 2012, 10:27:51 AM2/22/12

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Between what you'd connect the LED's anode to (the "LED" pin) and ground. But you can also just use the same method. Running the chips at 12v with a single LED lit won't hurt it since the heat dissipation is good enough for 35 LEDs. So turn the pot until the single LED turns off then turn it back a bit.

Cheers!
Andrew

Phil Spitler

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Feb 23, 2012, 1:38:25 AM2/23/12

to toasted-circu...@googlegroups.com, Andrew Stone

Hi Andrew, I just did some tests and my results were not as expected.

I have the 3 LEDs in series and they light up great after turning the pot until they all came on.

I then added one of my single LEDs to a different pin on the same IDE cable (as you said it wouldn't harm them if I used your 12v PSU).

I put the 3 LED setup inside a pingpong ball and also put the single LED inside another pingpong ball.

The 3 LED ball was brighter but I would expect it to be a LOT brighter (3x) but it isn't.

I am not using any resistors or an other components, just the Lightuino, the RJ45 breakout board and the same LEDs.

Any thoughts?

Cheers

Phil

On Feb 21, 2012, at 7:33 PM, G. Andrew Stone wrote:

Andrew Stone

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Feb 23, 2012, 1:02:01 PM2/23/12

to Phil Spitler, toasted-circu...@googlegroups.com

Its possible a lower current is running through the 3 LEDs (so each one is dimmer). You can test this by with your multimeter. If that is the case, then not enough voltage is being provided. So either the pot is not up high enough, or the voltage across the LEDs + the M5451 voltage (~.7) + voltage regulator drop is > 12v. Please test the transformer's output and if its at 12v or less you can supply the 3 series LEDs directly from it (its a regulated transformer). This actually will be best, because then you can use the onboard regulator to provide the lower voltage for your single LEDs.

Its also possible that its all working fine. The sensitivity of the eye is logarithmic with respect to brightness. So 3 times the energy (3 LEDs) will look less then twice as bright. Also, you may simply be getting a better light dispersal. I mean a single LED provides directed light illuminating one side of a ping pong ball, in a tight circle. So energy is dispersed by a small fraction (the size of the beam circle) of the square of the distance from the LED. But 3 pointing in all directions will disperse the energy as the cube of the distance.

Cheers!
Andrew

Phil Spitler

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Feb 23, 2012, 1:14:11 PM2/23/12

to Andrew Stone, toasted-circu...@googlegroups.com

Wow, great information. Thanks once again.

I'll test it tonight directly from the 12V PSU.

I was thinking of putting a photography light meter on the ball to see what the actual difference was.

I'll report back.

Thanks.

Phil

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