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Things You'll Need
Instructions
Construct a H-Bridge motor configuration using four transistors and a single DC motor. The standard H-Bridge design is created by connecting two transistors in series, and placing them parallel to another two transistors also connected in series. The motor connects the two circuits by placing each of its terminals in between the middle of transistors, forming the distinctive H shape the circuit is named after.
Attach the top two terminals of the H-Bridge circuit to the positive output of a 9 to 15 volt bench power supply, and the bottom two terminals to the negative output of the power supply. The power supply will be used to drive the motor and supply it with the energy needed to rotate the motor armature.
Connect each of the four transistors to a square wave pulse generator, using the gain junction if you are using a BJT transistor, or the drain junction if you are using an FET transistor. The square wave generators can now be used to switch the transistors on or off, with a high voltage pulse turning the transistor off, and a zero voltage pulse turning the transistor on.
Turning the transistors on or off in sets will rotate the motor clockwise or counterclockwise. Turning the top left and bottom right transistors on only will cause the power supply to supply a voltage across the motor from left to right, turning it clockwise; turning on the top right and bottom left transistors only will cause a voltage flow across the motor from right to left, creating a counterclockwise rotation.
Switching on either both the top or bottom transistors will cause the motor to brake instantly and stop faster than if it were allowed to slow down by simply cutting power to the motor. With this in mind, the motor can now be controlled digitally as a stepper, turning two of the transistors on for a couple of milliseconds to achieve rotation then switching another set of transistors on to instantly brake once the desired angle has been reached.