Here is a data sheet for a TIP31C ( Intelligent Power and Sensing Technologies | onsemi ). It shows that the base is terminal 1, collector 2 and emitter is pin 3. The base should wire to a series resistor and the other end of the resistor to the Arduino output pin. The emitter should wire to the Arduino ground and the ground of the +12vdc power source. The collector should wire to the device you are trying to control (lamp, motor, etc). The other end of the device should wire to the +12vdc voltage.
The missing information needed to properly size the resistor and to ensure that the TIP31C can indeed work for you, is how much current is your controlled device drawing?
The data sheet shows the TIP31C has a current gain of over 100 at that collector current so a series resistor of 500 ohms or so should work fine. Resistor wires between output pin and base terminal of the transistor.
retrolefty
I did say it was old memory...
Thanks for reminding me that that was the voltage used, not the recorded voltage. :
Your sheet does give the same gain, but additionally it specifies that the Base saturation is 375mA and that the C-E voltage should be 1.2v.
Hopefully pingy has overcome his frustration with soldering, and is able to measure if the switching is working now....
If all else fails pingy, often using a resistor power supply and a light bulb, without anything else quickly proves that damn transistor you sweated with for hours has had the smoke released earlier, and is nothing more than carbon, housed in a small plastic container with legs.
Mark
Ok lefty, I must call upon your thus far infinite wisdom one more time.
I am 98% there....really I am.
I got everything wired per the suggestions here and it all is working great..EXCEPT!
When the Arduino triggers the TIP31 my multimeter is going from 0 to only 2.x vDC ..its not making it anywhere close to 12vDC.
Now the only thing I can thing of is the fact that I put a 12vDC zener diode in series to stop the voltage spiking back. Could I have put the diode in backwards?
is this a valid symptom of having the diode in backwards?
...I thought I checked and double checked and triple checked how to install the diode, but at this point all I can think of is that it is backwards.
current flow top to bottom of the pic.
out the bottom of the transistor and into the zener diode, then out to my 12vDC load. Diode band is at the bottom.
I sure would like to see a drawing showing the whole thing including the load, however I can say I don't think I have ever seen a series zener diode used in a simple 12vdc switching application, did you copy that from some design, or are you winging it.
You normally see a reversed biased diode wired right across any inductive load device terminals (motor, solenoid, relay coil, etc). So try it without a the zener and try and provide a drawing (even a picture of a hand written schematic) if you want more comments.
When the Arduino triggers the TIP31 my multimeter is going from 0 to only 2.x vDC ..its not making it anywhere close to 12vDC.
Again without a drawing it's hard to see what and where you are measuring. You say it works, does that mean the load turns on and off under Arduino control?
It was indeed my zener diode was in the wrong way (wish i would have tested it before I soldered it down) oh well I guess 2 come in a pack for a reason!
thank you so much to everyone for your input (even that guy that just told me "search MOSFET")
Especially you lefty. I do not know why this transistor has me so confused but it really did.
