Hello, I have just gotten into Arduino and for my first project i'm doing the Luminch One. When looking for the NPN transistor, I was unable to find the specific one that was listed. I only want to buy from one of 3 sites that I trust, and none of them carry the exact model, but they do carry other models. Is there is a difference between the NPN BC337 and one of another model (say, a BC547 or a P2N2222A)? Can I use any NPN transistor? Thanks.
Is there is a difference between the NPN BC337 and one of another model (say, a BC547 or a P2N2222A)?
I believe the pin outs are different.
Always double check your E B C (emitter base collector) pin layout before hooking it up.
Google the data sheets for each.
So, what I found:
BC337 / BC547
Collector − Emitter Voltage VCEO: 45 / 45
Collector − Base Voltage: 50 / 50
Emitter − Base Voltage: 5.0 / 6
Would that last one cause this to not work correctly with the setup for the project? I did eventually find the BC337, but i'm new to all of this and trying to learn as I go so i'm asking this question any way 
There are many different parameters in a transistor, useful in different situations, which is why there are so many types. If you want to use a different transistor than the one specified, you must make sure that certain parameters, like current gain (also called beta or Hfe), are similar and that maximum limits are not exceeded. These include maximum power dissipation, maximum collector current, maximum collector voltage, and several others.
For your project, the high power LED current will be limited to about 150 mA by the 18 ohm resistor. That is OK for the BC337 (which can handle up to 800 mA collector current) but NOT OK for the BC547, which can handle only 100 mA collector current.
The 2N2222 would be a good substitute, but has a different pin configuration. If you can't find that one, pick a "general purpose" amplifier or switching transistor with a maximum collector current of at least 300 mA and medium to high current gain.
Edit: the parameters you posted, slightly before I did, are not ones you need to worry about. You need to worry about maximum power dissipation and collector current.
Just had one of those "ah-ha" moments there. Totally caught on to what you were saying. But, you said the pin configuration was different. Perhaps i'm looking at the wrong thing on the data sheet?
P2N2222A
BC337
If i'm reading it correctly, they have the same case and style number. The collector, base, emitter are on the same pins. Am I reading this correctly? I think I will go with the P2N2222A. It comes from the same site that more than half of my materials are from so that makes things a little bit better.
Now if the pin configuration is not correct, does that mean I have to put the transistor in a different way?
As for the LED, would the type I use matter? The one from the original product is no longer available, but if i'm understanding you correctly, the resistor is limiting it anyway. So if I were to get an LED that put out higher, it wouldn't be too big of a problem? This is what i'm looking at:
matrix86:
So, what I found:BC337 / BC547
Collector − Emitter Voltage VCEO: 45 / 45
Collector − Base Voltage: 50 / 50
Emitter − Base Voltage: 5.0 / 6Would that last one cause this to not work correctly with the setup for the project? I did eventually find the BC337, but i'm new to all of this and trying to learn as I go so i'm asking this question any way
The Vbe (base-emitter) reverse voltage limit is always about -5V and it should never matter
as you should not be driving the base negative at all.
If i'm reading it correctly, they have the same case and style number. The collector, base, emitter are on the same pins.
Case style and pin configuration can be different, for the same type of transistor but from different manufacturers. The 2N2222 data sheet you linked is from a different manufacturer than the one I use. Make sure that you have the data sheet for the transistor type and manufacturer that you intend to use.
You can use a different high power LED in that circuit. However, a low power LED would be destroyed by excess current.