You want 300-350mA; that eliminates 2N3904. PN2222 and 2N4401 can handle the current, but can they handle the power.

What is an 8050?

That circuit will only give a constant current if the voltage source is stable.

its going to be powered by a 9 volt switching power supply which really puts out 9.4. as for the 8050, i dont know its what it is labeled as.

 

but what about the whole deal with just using a resister for longevity is not good enough due to fluctuations? I want this to last for it is part of a gift.

What variations?

If you have a regulated 5V supply, and it does not have to operate at extreme temperatures, the resistor will be just as robust as any other driver you come up with.

I have been running RGB LEDS, 1W each color, for years without problems.

KI SS

Bob

 

What variations?

If you have a regulated 5V supply, and it does not have to operate at extreme temperatures, the resistor will be just as robust as any other driver you come up with.

I have been running RGB LEDS, 1W each color, for years without problems.

KI SS

Bob

im using a 9 volt switching supply. Everything i read says you can use a resister but you should use a constant current driver...

 

Everything i read says you can use a resister but you should use a constant current driver...

If you are using multiple LEDs and care about brightness matching, you need to use a current source/sink.

 

If you are using multiple LEDs and care about brightness matching, you need to use a current source/sink.

decided to just use one 1 watt led

 

decided to just use one 1 watt led

Are you just using one LED?

 

decided to just use one 1 watt led

So for that a resistor will be fine.

 

1W is a lot of heat in an LED. How will you cool it?
Post its datasheet for us to see the recommended way it is cooled.

 

Youcan build a current regulator with a 3-terminal regulator IC and one resistor. That is about as simple as it gets, And the regulation is as good as the regulator. The circuit has the regulator input connected to the positive supply,and the common terminal connected directly to the load, and the output also connected to the load through a resistor with a value to provide the rated regulator voltage at the desired regulated output current. Also there is a 0.1 MFD capacitor connected between the regulator common and the regulator output, using very short leads.
As an example, using a 5 volt regulator to deliver 100milliampos, V=5, I=0.1A, so R=V/I=5v/0.1a=50 ohms.
So you do need to know the intended LED current, AND the supply voltage needs to be at least 5 volts greater than the LED forward drop at it's rated current.
This regulator is not the most efficient but sometimes accuracy and simplicity outweigh efficiency.

 

This regulator is not the most efficient but sometimes accuracy and simplicity outweigh efficiency.

Don’t see any requirement for accuracy here, and simplicity favors a single resistor. Now, if it was a 10 Watt LED my answer would be different, but it would still not be a constant voltage supply of 9V and a current regulator.

Bob

 

What caused you to switch from using “ a USB power supply if possible, or 12V” as stated on the original post, to using a 9V supply that is actually 9.4V ( indicating an unregulated supply?)

The USB supply is not only possible, but a far better choice than either a 12V or 9V supply,

Bob

 

1W is a lot of heat in an LED. How will you cool it?
Post its datasheet for us to see the recommended way it is cooled.

1636581.pdf (farnell.com)

 

What caused you to switch from using “ a USB power supply if possible, or 12V” as stated on the original post, to using a 9V supply that is actually 9.4V ( indicating an unregulated supply?)

The USB supply is not only possible, but a far better choice than either a 12V or 9V supply,

Bob

because I didn't have a small enough resister to get the brightness i needed on 5 volts and I couldn't find a 12 volt that was not being used for something.

 

Ah, design guided by part availability. Actually, the higher voltage makes the resistor a better current regulator, but at 9.4V, you will need a 2W resistor minimum, and it will get quite hot.

Bob

 

It looks like the copper on its pcb carries away heat from its solder pads and under its "slug".

 

because I didn't have a small enough resister to get the brightness i needed on 5 volts

How about using two or more resistors in parallel to get the low resistance you need?
That will save a lot of power.

 

Ah, design guided by part availability. Actually, the higher voltage makes the resistor a better current regulator, but at 9.4V, you will need a 2W resistor minimum, and it will get quite hot.

Bob

yeah im using 2 watt resisters and yes that mf got really hot

 

How about using two or more resistors in parallel to get the low resistance you need?
That will save a lot of power.

lol, because the next one down that i have is 0 ohm.

 

Don’t see any requirement for accuracy here, and simplicity favors a single resistor. Now, if it was a 10 Watt LED my answer would be different, but it would still not be a constant voltage supply of 9V and a current regulator.

Bob

The forward voltage drop of an LED varies quite a bit with temperature, and thus if the operation is to be stable and near the maximum safe current it needs to be stable.
But now I see that parts availability and size are also variables in the design..

 

The forward voltage drop of an LED varies quite a bit with temperature, and thus if the operation is to be stable and near the maximum safe current it needs to be stable.
But now I see that parts availability and size are also variables in the design..

yea.. like i said in the beginning I'm kind of new. therefore I don't have every value of everything but a good little chunk of everything...