Hi! I am trying to make a 3d scanner for a science project and for this, I need to move motors back and forth across a threaded track. In order to move the 12V DC geared motors back I would need to put (-) to the (+) terminal of the motor. Doing this physically with your hands would be easy; just cross the wires, but I have had a bit more difficulty doing this with a parallel port of a computer. My thoughts are using 4 transistors as seen below in the picture attached.
Basic Idea:
My thoughts would be send 5V through one data terminal on the parallel port to 2 transistor bases and have the emitter connected with the parallel port ground. Then the motor would go forward. To make the motor go back I would send 5V through a different data pin to the other 2 transistor bases. I wouldn't send current to the first 2 transistors. This is description is vague and incomplete, but writing another page or 2 of description would probably be boring to read (even more than it already is!
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I tried this with a 3V watch battery as a parallel port output and a 9V battery input, but it didn't work. (I tested with a multimeter not 12V motor)
-Is my logic off?
-Did I accidently fry the transistors in soldering process?
-Is 3V and 9V above the limits of a tipical NPN transistor?
-Did I mess up some where in the soldering process?
Sorry for the lengthy post! If anyone could offer any assistance that would be awesome!
I am fairly new to electronics if you can't tell, so this one is getting quite frustrating.
Thanks! Please tell me if you have any questions!