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Topic: What are transistors. (Read 7978 times) previous topic - next topic





Understanding what I can do with transistors

Hint: You're using several million right now.
"Pete, it's a fool (who) looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.
I speak for myself, not Arduino.


Get a new transistor.

Emitter to ground.
Base to a 1K resistor.
Other end of the resistor to you arduino output pin.
Collector to the LED's current limiting resistor, say 220R
Othe end of this to the cathode of the LED.
Anode of the LED to the positive supply.

Now turning the arduino pin on and off will turn the LED on and off.
The small current flowing in the base that is limited by the resistor to less than 5mA will switch the large current of 20mA lighting up the LED.



nothing is working

Then your doing it wrong. Post a drawing of what you are trying to wire up.



Then you have either wired it up wrong, got the LED round the wrong way or you have a faulty transistor. Did you replace it because your previous circuit would have distroyed your previous one.

Have you set the arduino pin to the output mode in the setup() function?


should it fade like a resistor


well, the code is the BLINK
i just changed the delay function to 1


That will blink faster than you can see and so should look half on. When you say nothing works exactly what to you see?
You should have a delay of something like at least 500 to give half a seconds delay.


i'm gonna come back in 20 minuts.


I only see two wires connecting your circuit to the arduino, there should be three. A 5v, a ground and a signal from pin 13.


guesse what, my red led is dead.
and i felt really the transistor really hot after touching it


The transistor should not be hot check you have identified the leads correctly. Also have you sorted out the missing wire from those photos?


can you put photo of it, its gonna be easy for me to plug the wires



I look at your picture, and I want to know what type of transistor you are using - NPN ? PNP ? MOSFET ? What ?  Well you can tell by the number/letter in front of the transistor.  The one you are using is a TO-220 <-- Package type. That tell me it is a "power type" I can handle a few amps.. And yes IT WILL get HOT !! if a lot of currents go through it. ( need a heatsink ) Here the site I use when I have a number/letter of a unknow transistor. http://www.datasheetcatalog.com/

Ok for exammple, the number 2N3904 is a NPN small signal general purpose - TO-92 package can only handle small current.

Small current ===> a street  ( low traffic )  A high current ====> a 6 lane highway ( high traffic ).

And please tell us the number of that transistor you are using.

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