Can You Use a Dc Motor Controller?
NO! Do not do because a DC motor controller puts DC current into the circuit who acts as control, or, puts a variable voltage across it to define the speed of the controlled motor. You need to (in most of the situations) control the phase angle to make a variable speed and the power supplied to the motor. Good luck.
1. Drive DC Motor with H Bridge(H Bridge turns off too slow and problem with current monitor)
To switch a power MOSFET, you have to move a substantial charge through the gate and the source. The datasheet will specify something like "total gate charge". In order to move all that charge in a short time, you need high current. And in your circuit you can not have high current, since the current through the gate is ultimately limited by R1 and R3.In other words, the problem is that with your design, U1B does not fully turn off until some time after S1 goes low. And when it does turn off, it does so slowly, which is why you see the voltage at T1 ramp down slowly. See What is MOSFET gate drive capability and why do I care about it?In order to reduce this problem, you need to increase the current that your gate driver can source and sink. A simplistic solution is to add a pair of emitter-followers, like this:simulate this circuit - Schematic created using CircuitLabYou can get fancier with a discrete approach like the one that follows. In addition to having emitter followers to increase the current drive, it uses a clamp (D13, D23) to reduce the storage delay of the BJTs Q11 and Q21. You can read more about it in another answer.Or, you can just buy an integrated MOSFET gate driver and call it a day
2. Will a dc motor generate as much power as it can put out?
Nope... motors & generators are not 100% efficient, thus power out is always less than power in, regardless of the direction of flow. For a smaller motor like that you are probably looking at around 20% loss from input power to output power. With a higher mechanical input power (>6500 rpm at 5in-oz) you might get 150W electrical output, but I would look pretty carefully at the manufacturer's data to be sure you are not overheating the windings.
3. DC motor and encoder for pendulum with low static friction
Actually, you need to rethink your controller. As stated, forcing the motor voltage to zero will cause the motor to provide a large damping force to the pendulum. The reason is that any motion of the motor shaft will cause the motor to act as a generator. Keeping the motor voltage at zero is effectively the same as providing an extremely small resistance across the motor (E = iR, after all), and this will resist any motor motion. So simply controlling the motor voltage will not allow the pendulum to swing freely, regardless of friction
4. Question about a DC motor comutator?
The commutator bars are the strips of copper mounted arount the perimiter of the commutator . As you pointed out each commutator bar is connected to the end of an armature coil. You are correct in your observation that a brush can bridge across two commutator bars during the transisition of switching from one set of coils to the other. Since the armature coils are wound in the same direction and are mounted along side one another the electricity produced in these adjacent coils is inphase and at similar (but not equal) voltages. In effect during this breif period where a brush bridges between two adjacent commutator bars the effect is like having two armature coils in parallel. During this change over period two coils share the load so current does drop in one coil as it increases in the other coil. BUT !!!! You have forgotten to consider that the voltage produced in the armature is constantly changing and is actually an AC sine wave. Maximum potential is generated as the coils cut across the magnetic line of flux where they are concentrated at the field poles and also at a right angle to the coils movement. At the coil continues to rotate away from the field pole the flux density decreases and motion of the coil tend to travel in parallel to the lines of flux. the result is little to no voltage is produced. Again this is illustrated in an AC sine wave which shows a constantly changing level of voltage between zero and peak Pos and neg voltages. In order to minimize brush sparking and major changes in current flows in the armature coils, the brushes are located at an angular position with respect to the rotor where the AC sine wave voltage produced within the armature winding is at a zero or near zero value. So the switching of the coils and the bridging of the adjacent commutator bars which you are questioning is happening at a point in the armature rotation where there is little if any voltage being generated in the armature. The effect is temporarly placing two armature coils in parallel to each other as the gap between two adjacent commutator bars passes under a brush. This is one of several reasons why the
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