Motors 2/16

At the end of class on Monday we began talking about motors so that we could build circuits with motors in them on Thursday. This is what the circuit we built looked like:

In our circuits we connected the motors to an op-amp with negative feedback to create a virtual ground where the motor connected to a resistor and the input voltage. There is a virtual ground because V- wants to be the same as V+ since this circuit has negative feedback. V+ is connected to the ground, so V- is 0V. This allowed us to control the current going into our motor by changing the resistance with our potentiometers. By changing the voltage coming out of our potentiometers between -12 V and +12 V we were able to change the direction that the wheel moved on our motor. Then we put another potentiometer on our circuit so that the output would measure only the speed of our motor.

  The potentiometer created a voltage divider that canceled out a value in the equation of the motor so that we could measure the speed of the motor.
  The motors we used were pretty cool because they were Lego motors.  I think that the Lego's educational stuff is pretty cool, and I think it is very interesting that they are now making Lego sets marketed specifically for little girls. I wonder if this help lead to more interest in engineering for girls?  There are so many Legos in that room, I hope we get use them. I would honestly be pretty happy if we played with Legos the rest of the semester!