A transistor I am using refuses to complete a circuit I have after putting 5 volts into the base through an arduino digital pin. I have the transistor between the 2 positive leads of a motor and my battery pack (I have tried flipping the connections to make sure it was not backwards ). I have run out of possible solutions.
The transistor in question is NTE 288.
A search of previous question yielded this posting:
http://techhouse.brown.edu/~dmorris/projects/tutorials/transistor.switches.pdf
May be it will help your situation as you have provided no details on your circuit for others to analyze.
My Circuit
+(Battery)---C(Transistor)B(Transistor)E---+(Motor)
|
|
5v (Arduino digital pin)
Picture for a better look 
That's a PNP transistor so you ground the base for "on".
Hmm im looking at the schematic on that link to try to understand it.
It seems i need to use resistors but being a noob i have no idea why (Yes im reading it).
That arrangement won't work at all with a PNP transistor.
Yes, you MUST have a base resistor, or you will damage the Arduino. Start with 1000 ohms.
The "circuit" is not complete. Where is ground? What is the battery voltage?
Forget the photo of blurry wires, instead draw out the circuit diagram by hand, and post a photo of that.
Heres a quick diagram of my current circuit i have drawn up. Im sorry about the bad handwriting haha. Question: Why do i need a 1k resistor on the base lead?
Note: Those negatives are connected to only each other, not in anyway attached to that positive lead from the arduino.
@Crossroads ya that makes sense, just some questions about it so i fully understand.
No it's not just that the transistor and motor swapped places: look at the transistor symbol.... one's an NPN (motor above it), the other os PNP (motor is below.)
NPN is "on" (= motor runs) when base is high, eg from Arduino. PNP is "on" when base is low, eg yes low as in digitalWrite. NPN and PNP have reversed logic.
Resistor:
(5V-0.7)/.03 = 150 ohm up to 1K.
You want the transistor to be full on (i.e. saturated).
I need to get my terminology straight CR..... is a PNP on or off when saturated? I'd call it "off" in the sense that the CE circuit is broken, but it's "on" in the sense that the transistor is active.
PNP - Low at base turns on the transistor.
NPN - High at base turns on the transistor.
When enough current flows (from the base for PNP, into the base for NPN) the transistor will saturate. The transistor spec will show Vbe (sat) to show you voltage from base to emitter when that happens and how much needs to flow.
What does "Saturated" mean with the transistor? Im also still trying to understand the resistor purpose, am i trying to drop the voltage to something specific for a reason?
Looking at my code i actually already set the output of the arduino to LOW for 5 seconds as well as HIGH but it still did not work. Will try to set it up like that diagram above after i figure out the resistors.
Sorry for all the questions but i really dont understand alot of the things its probably assumed i would already know 
Resistor keeps Ardiuno output from sinking (when low) or sourcing (when high) to much current.
Base-emitter junction of transistor looks like a diode - when diode voltage reaches it's Forward Voltage (Vf) it turns on with low resistance - hence the need for external resistor.
See "transistor as switch":
h4344:
What does "Saturated" mean with the transistor? Im also still trying to understand the resistor purpose, am i trying to drop the voltage to something specific for a reason?
Saturated means the collector-emitter voltage drops to a low level, perhaps 0.2V,
allowing lots of current to flow without generating too much heat in the transistor.
Without a resistor on the base you will damage the transistor or Arduino or both since
far more than 40mA will flow. Use a 150 ohm resistor to get maximum "safe" current
from the Arduino at 5V, namely about 30mA. If 30mA isn't enough to saturate the
transistor you might be better off with a MOSFET.
Looking at my code i actually already set the output of the arduino to LOW for 5 seconds as well as HIGH but it still did not work. Will try to set it up like that diagram above after i figure out the resistors.
Sorry for all the questions but i really dont understand alot of the things its probably assumed i would already know
BTW you realize that the switching transistor must be wired collector to the load? Some
of the diagrams earlier in the thread are just wrong.
For an NPN switching transistor its done like this: http://elinux.org/images/7/76/Npn_switch.png
If the load is inductive you need a freewheel diode across the load, like this:
http://makezineblog.files.wordpress.com/2009/02/arduinorelay.jpg
