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October 30, 2005
Labs
Tomorrow.
Crunch-time for pcomp labbing!
Transistors, relays, midi (will be working on it with Todd M) and the H bridge. Thank you Todd H. You ROCK!
Transistor schematic
The relay
A relay is a switch that's controlled by a small electric current. Relays take advantage of the fact that when you pass an electric current through a wire, a magnetic field is generated surrounding the wire as well. When you place an iron shaft inside a coil of wire and pass current through the wire, the magnetic field moves the iron shaft. If that iron shaft is part of a switch, the switch can be turned on and off by putting current through the coil, which moves the shaft, closing the contact
H bridge, SN754410NE to control the direction of the DC motor
DC motor
There are two terminals, and when you apply direct current to one terminal and ground the other, the motor spins in one direction. When you apply current to the other terminal and ground the first terminal, the motor spins in the opposite direction. By switching the polarity of the terminals, you reverse the direction of the motor. By varying the current supplied to the motor, you vary the speed of the motor.
H bridge, ULN2004KN for the stepper motor
The stepper motor. The stepper motor is different from a regular DC motor in that the user could have control over its rotation angle.
The stepper motor bought from James' garage sale a while ago... 3 dollars! :)
A stepper motor is a motor controlled by a series of electromagnetic coils. The center shaft has a series of magnets mounted on it, and the coils surrounding the shaft are alternately given current or not, creating magnetic fields which repulse or attract the magnets on the shaft, causing the motor to rotate.
This design allows for very precise control of the motor: by proper pulsing, it can be turned in very accurate steps of set degree increments (for example, two-degree increments, half-degree increments, etc.). They are used in printers, disk drives, and other devices where precise positioning of the motor is necessary.
Posted by min at October 30, 2005 01:55 AM