And yet more L.E.D.'s

[Putt]

looking at the 7443 "wedge" led, arranged to bounce light off
of the reflector.....

7443... ten bucks each...

http://autolumination.com/specifications.html


Putt...

[crazykz]

I like these. I'm trying them out as a reading lamp.

http://www.lumileds.com/products/family.cfm?familyId=2

I'm using the Star/O with a lens.

Curt

[crazykz]

Ok dudes. I finally got the resistor I needed to fire this sucker up. I'm driving the Lumiled LED at ~330mA which is just about the max of 350mA. Show me another LED that you can drive over a 1/4 of an amp through.

The one shot is the LED shining on the ceiling from 8 feet away. The shot is from 10 feet away and is not zoomed in.

I have a 5 Watt resistor hooked in to limit the current and prevent the LED from frying which is what I did with the first one. Oops. And you guys think I know what I'm doing. HA!

I'll include a circuit picture of this so you can see what's happening. Maybe a little Ohms law refresher. I know you love that crap.

Ok here it goes:
I started with the fact the I get 13.8V from my convertor and if the electrical on the bike was running correctly that's about the max I would get.

So normally you would start with the voltage and some resistance but in this case I have a diode and although it does have a resistance isn't the limiting factor so with a diode (LED) you have to look at the max amount of current for the LED which is 350mA. But you also need the minimum voltage drop across the LED which from the documentation is 2.8V. That means we have to get rid of 13.8-2.8 = 11 Volts.

So we need a resistor to drop the rest of the voltage before we connect the circuit to ground. Resistance limits current and we want to make sure that we don't exceed 350mA or we will fry our LED. I got in a rush and fried one without remembering to do that. Just wasn't thinking.

Using Ohms law we have 11 Volts and 350mA so 11/.350 = 31.43 Ohms. Now that's the minimum resistance we need to add to our circuit. We don't want to drive the crap out of the LED we should probably add a little more to this value plus resistors only come in certain values so the closest standard resistance we can get is 33 Ohms. Now I could use a higher resistance and maybe I should but that's what I got so that's what I used. Now the last part of this is power. Power in a resistor is dissapated by heat so the amount of surface area is important. The physically bigger a resistor is the more power it can disspate. If we know the current is 350mA max and the voltage across the resistor is 11V then by Ohms law (P=I*E) 11*.350=3.85W. That's a lot for a little circuit. Typically resistors are 1/4W in small voltage circuits but since we have almost a half amp there's a lot of juice flowing here so we need a small resistance but the resistor must be able to dissapate 3.85W of power which will generate a decent amount of heat. So the power rating of the resistor must be greater than 3.85. 5W is one we can get so I used that. It has about the same surface area as a cube of sugar. That's big.

This isn't a detailed explanation but I included a the circuit diagram and what I measured at each point. I'll summerize what I had to start with and what I measured in the actual circuit.

LED: 350mA max, 2.8V minimum
Supplied Voltage: 13.8V maximum

Total Voltage - LED Voltage Drop from Documentation = Voltage Drop across resistor needed for circuit.
13.8V - 2.8V = 11.0V

Resistor Voltage / Diode's Max Current = Minimum Resistance needed to keep current in the circuit under 350mA
11.0V / 350mA = 31.43 Ohms (closest resistor is 33 Ohms)

Resistor's Voltage Drop * 350mA max current = Power value for resistor
11 * .350 = 3.85W

The picture of the circuit I drew up reflects the measured values.
Supplied Voltage: 13.8V
Resistor: 33 Ohms (5W), drops 10.8V
Current: 330mA (in a series circuit, which is what this is current is the same through the whole circuit. Why? Because there is only one path for current to flow from the positive terminal to ground. It can't go back through the power source, it doesn't work like that. It's like water through a garden hose. It only has one way to go out the other end unless you make more connections and split up the water to flow to multiple hoses but then the amount of water is split between mulitple hoses. It's the same with current. If you have multiple paths in the circuit then they must split up the current through all the legs.)

So the actual and measured are slightly different but for the most part it's all right on and it works. We're getting as much current through the LED which will give us the most light. Of course that also gives us 4 watts of heat and we're driving the light very hard which may shorten it's life but we'll see.

Curt

[nm6r]

I'm anxious to see the results of some of these LED assemblies in a real world application. Like the ST1300 taillight. Is enough light directed to the reflector?

Curt has me wondering how he's going to use that killer 4 watt LED on his ST. Imagine an array of those?

Ray
http://www.frontiernet.net/~st1300rider/smile04Bikerwheelie.gif

[crazykz]

I'm anxious to see the results of some of these LED assemblies in a real world application. Like the ST1300 taillight. Is enough light directed to the reflector?

Curt has me wondering how he's going to use that killer 4 watt LED on his ST. Imagine an array of those?

Ray
http://www.frontiernet.net/~st1300rider/smile04Bikerwheelie.gif

I'm going to use it as a map reading light. I have it boxed up with a switch but trying to aim it at the top of the tank bag is going to be a challenge.

Curt

[Putt]

Curt,
Put a 0-1000 ohm or 0 - 500 ohm 5 watt pot/rheostat in series with the load resistor, that way you can controll the brightness of the L.E.D. Even though the
L.E.D. is red, if it is too bright it will still temporarily play havoc with your
night vision....


Putt...

[crazykz]

Curt,
Put a 0-1000 ohm or 0 - 500 ohm 5 watt pot/rheostat in series with the load resistor, that way you can controll the brightness of the L.E.D. Even though the
L.E.D. is red, if it is too bright it will still temporarily play havoc with your
night vision....


Putt...

Thought about that but I want to try it before I blow more money on the project. We'll see. I want to do some more experimenting first. I would like to mount the light but with the little box I have the angle I need is going to be hard. Again we'll have to see.

Curt

[crazykz]

I'm anxious to see the results of some of these LED assemblies in a real world application. Like the ST1300 taillight. Is enough light directed to the reflector?

Curt has me wondering how he's going to use that killer 4 watt LED on his ST. Imagine an array of those?

Ray
http://www.frontiernet.net/~st1300rider/smile04Bikerwheelie.gif

BTW these LED's are used for reading lights on airplanes. Well at least the white ones. I bought 2 red ones and 3 white ones.

Curt

[pmorritt]

looking at the 7443 "wedge" led, arranged to bounce light off
of the reflector.....

7443... ten bucks each...

http://autolumination.com/specifications.html


Putt...

Putt, are you going to put those led'd (7443) in the two brake light housings? Are they 2 element equilivent? Would love to hear how they work and perhaps a pic--Phil:biker:

[Putt]

Ok, how about this?

controller box in one of the pockets, (on off switch/pot/resistor mounted
so you can adjust them on the pocket door) small 2/3 pin polarized plug, L.E.D. affixed to your helmet (top, pointing forward) Turn your head which ever way you want the light to shine..
If you run 3 wires, you could use one of the red ones and one of the "white"
ones (2 hot, 1 common, on-off-on toggle switch).
We can find all kinds of ways to spend money!!!

Putt...

[ligito]

"I'm going to use it as a map reading light. I have it boxed up with a switch but trying to aim it at the top of the tank bag is going to be a challenge."

Maybe mount it on the tank bag.

[Putt]

Putt, are you going to put those led'd (7443) in the two brake light housings? Are they 2 element equilivent? Would love to hear how they work and perhaps a pic--Phil:biker:

Phil,

For ten bucks each, I think I will give it a try.... Even if it is no
better than the filament 7443's I won't ever have to worry about
replacing them...

Putt...

[pmorritt]

Putt, rgr that. Think i will also. Can't ever have enuf light-ft or back.

[Biddyman]

http://www.st-owners.com/forums/attachment.php?attachmentid=5977&stc=1&thumb=1&d=1135998271 (http://www.st-owners.com/forums/attachment.php?attachmentid=5977&d=1135998271)

Curt,
Is that the remote in the background for your new DVD player installed on the dash so you don't get bored on those long trips?

[crazykz]

http://www.st-owners.com/forums/attachment.php?attachmentid=5977&stc=1&thumb=1&d=1135998271 (http://www.st-owners.com/forums/attachment.php?attachmentid=5977&d=1135998271)

Curt,
Is that the remote in the background for your new DVD player installed on the dash so you don't get bored on those long trips?

Yes, how did you know?

Curt

[ccryder]

Too bad no one, so far, has this style bulb in the 7443 base. This is what we need to properly illuminate our stoplight and license plate. The LEDtronics lights are pricey but they really put out a lot more light than the cheaper LED's. Not all LED are created equal. I comared some Autozone 1157 LEDs to the LEDtronics and you could barely see the Autozone lights in full sun. Even in full sun the LEDtronic bulbs you knew they were lit in running mode and in brake mode there was NO question.

Neil S.