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Transistor question Answered

Hey guys I have a question on transistors. When using for PWM setups, is the difference between each NPN (or PNP) transistor model by its specs? Such as gate voltage, max current, etc.

I am making a LED touch setup made by qs, but I want to make it so that the Arduino activates a transistor to turn on a string of lights that the arduino could not power on its own.

Here is the setup of the LED string. I want to replace the TIP31 in the wiring diagram with a NPN transistor (like this one). By replacing it, which pins go to which wire and do it have to add anything else to the setup? Will the new setup also work with PWM signals?


KT Gadget


So I had a question regarding the led strips and how you connect it with the arduino's. So Im looking at using a IP-65 rated 12 V RGBW 3.5 Watt Led strip and to connect it to the arduino, I need a transistor. My main question regarding that was, what transistors do I use, or which is the best transistor to use for this project since it's going to be a long term thing. Also, its a large scale project (about 45' long).
Thank you

The TIP31 is a power transistor, the 3904 isn't built for the same current. It'll work in the same way, and you wire it up in the same way (match B, C & E the same way).
Just be careful not to exceed the 3904's current rating.
(That is essentially what Goodhart said though)


I plan to only use maybe 100mA max on each transistor I'm using, so I will be well below the max rating of the 3904. KT

Yea, go for it, just match B, C & E. L

KT, here are some of the "pinout" data sheets for the TIP31 http://www.datasheetarchive.com/TIP31-datasheet.html Now, comparing the Emitter,  Base,  and Collector designations of the TIP31, you can then figure out how to solder in any other transistor you would want to use....just be careful to read the rest of the data sheet for your transistor,  in as much as if you draw more power then it can handle, you'll fry the transistor as soon as you throw the switch.

The only major difference between the two transistors (voltage-wise) is the Emitter-Base voltage; TIP31 is 5v max while the 2N3904 is 6v max. In this case, the 2N3904 will work with PWM signals of 5V?

well, several other things jump out ...like tip31 collect current dc = 3 A and the 2n3904 = 200 mA This amperage difference, may not make a problem for you either though. For your application, any differences in switch time is negligible.

Alright cool. Thanks for the help! Hope I can get this project going.

You need to Google "(part number) datasheet" if the transistor didn't come with one. If you're referring to a specific-build please link it. L

Hey lemonie, I just edited the post with three links of two projects and the part I have that I want to use. KT