How long it took you?

[RobEU]

I am a bit lost now - I am VERY stupid, or its just not that easy. Its coming so hard to me understanding electrics. Also, some confusing texts like "driven at 700mA" are making this more complicated for me. As far as I understand, you dont feed amps into led, you feed volts and led gives back amps. Why not say "driven at 20v" it gives xxxLm?

How long did it take you to learn and fully understand volts and amps things?

 

[robvantour]

It is actually not that hard to understand.
LEDs give a certain amount of photons per electron.

If you drive the LED at a constant current the LED creates more or less the same amount of photons for different temperatures.

If you drive it at a constant voltage, that implies a certain current at a certain temperature. When the LED heats up, its resistance will grow and therefore the current will decrease.

Constant current means constant amount of light.

And yes, a difference in potential will create a current.

 

[Tekno_Cowboy]

It's not too difficult. Just keep at it and you'll get it :thumbsup:

 

[matrixshaman]

Study Ohm's law and the several equations it uses. That will help a lot and they are not that complex if you know basic algebra. Electronics can be complex and I'm sure a lot of people here who are talking about drive currents and making designs or mods have had electronics in school but for the purpose of flashlights and a basic understanding of what many talk about here it's not that complex if you know Ohm's law. A couple examples:
E= Electromotive force in Volts
I= Current in Amps
R= resistance in Ohms
P= Power in Watts

E=I x R
P= E x I

From those two you can derive many other equations with simple algebra.

 

[rje58]

I am wanting to learn more, as well. Are there any good primers, tutorials, references, etc. for things like Ohm's Law, 'modding for beginners' and related topics?

 

[45/70]

You guys might find this helpful. It's one of the many interesting topics in the "Threads of Interest" sticky at the top of this Forum.

Dave

 

[Mr Happy]

Also, some confusing texts like "driven at 700mA" are making this more complicated for me. As far as I understand, you dont feed amps into led, you feed volts and led gives back amps. Why not say "driven at 20v" it gives xxxLm?

Because you really do feed current into an LED, or at least you have to think that way. An LED does not behave like a normal resistance, so if you try to apply a fixed voltage to an LED you will not be able to predict the current reliably or consistently. It will be very easy to damage the LED.

Therefore, when you drive an LED you have to use some mechanism that restricts or regulates the current in a suitable manner. When people say an LED is driven at 700 mA, it means that something is done to make sure the current stays at 700 mA and does not float up or down.

The idea of driving lamps by current is not unique to LEDs. Incandescent lamps are sometimes driven by current as well, for example in the case of airfield lighting systems, or street lighting a very long time ago.

 

[PeAK]

I am a bit lost now - I am VERY stupid, or its just not that easy. Its coming so hard to me understanding electrics. Also, some confusing texts like "driven at 700mA" are making this more complicated for me. As far as I understand, you dont feed amps into led, you feed volts and led gives back amps. Why not say "driven at 20v" it gives xxxLm?

How long did it take you to learn and fully understand volts and amps things?

It is voltage that induces or "drives" current. Slang has given leeway to use of phrases such as 'driven at 700mA' being acceptable. You can make a fairly direct analogy between driving LEDs with slightly differring resistances to pipes with differring diameters. If we applied the same pressure to both, the larger diameter pipe would have a greater flow (equivalent to current). If I ask someone to make the "flow" (analog: current) to be a specified number/rate, then we would need to vary/lower the pressure in the larger diameter pipe until the flows (analog: current) were equal.

So a current source is basically:

"a source of variable voltage such that it puts out whatever voltage is needed to 'make' the current the specified value"
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[rje58]

Thanks! I appreciate your mentioning that! I had checked the stickys at the top of most of the forum topics, but I missed that one here in 'Batteries'.

You guys might find this helpful. It's one of the many interesting topics in the "Threads of Interest" sticky at the top of this Forum.

Dave

 

[RobEU]

I am wanting to learn more, as well. Are there any good primers, tutorials, references, etc. for things like Ohm's Law, 'modding for beginners' and related topics?

See "Analog eLab Videocast series - Powering LEDs" video on this link:
http://focus.ti.com/general/docs/gencontent.tsp?contentId=28887

VERY useful.