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Transistor Related Questions? Answered

Hey Guys,

I need some help, I need to choose a transistor and get to know how to wire it. I have the following transistors:

6822 (http://pdf1.alldatasheet.com/datasheet-pdf/view/604250/ALPHAWIRE/6822.html)
2N3904 (https://www.sparkfun.com/datasheets/Components/2N3904.pdf)
2N2222A (http://www.onsemi.com/pub_link/Collateral/2N2222A-D.PDF)
TIP42C (https://www.fairchildsemi.com/datasheets/TI/TIP42.pdf)

And I need help to choose one that can run an Green LED Strip (16 in.). And also how to wire it. If you can give me the steps to wire it up to the output of a circuit and how to wire it up with the led strip it will be greatly appreciated. Oh and also the voltage at which the transistor turns on should be 2.8-9v ish.

Thanks in advance.
-Prickly Potato


2N3904 and 2N2222 are almost the same 40 volt .5 watt NPN transistor.

TIP42C is a 100 volt 65 watt PNP transistor.

Don't get much useful information on the wire other than the TIP42C would probably be better.

Beyond that what do you want to do?

Do you just want to turn the LED strip on because you can do that with a resistor and a switch.

Do you want to connect it to a flasher so it turns on and off to a timer or audio input?

Dumb me I did not realize it was the same author.

You can get datasheets here http://www.maxim4u.com/

Down load the datasheet so you are sure which pin is which.

TIP42C is a PNP transistor so the emitter goes to source voltage and the collector goes to ground and the base is your negative signal in.

So positive voltage from source comes in the emitter and goes out the base to ground and out the collector to ground.

Since you want to use the PNP transistor as a switch you need a negative charge at the base.

With that audio circuit you want the 2N3906 emitter connected to the base of the TIP42C not source voltage, and the collector of the 2N3906 connected to ground.

Then you can have the LED strip ether between the TIP42c and source which is where I would put it, or you can have the LED strip between the TIP42c and ground which should work just as well.

Does that help?

There are datasheets that will tell you the pinouts and electrical values.
If you are unable to use those I strongly suggest to buy a controller for your strip - 3 bucks well spent...


2 years ago

To select the most optimal transistor (more strictly speaking, what driving circuit), you need to have an idea on how you are going to drive your LED. What voltage and current does it need? What power supply do you plan to use?

Really if all you want to do is switch the LEDs on and off, just use a MOSFET like the IRFZ44, which might be a bit overkill for small LEDs, but that's not a problem.