Text-only reference. Published from the recorded official FAA General Chapter 12 PDF. Diagrams, photographs, and figure artwork are not reproduced here; use the official FAA PDF for those materials.
12-123 High Leading edge Low Trailing edge Positive logic pulse Negative logic pulse Trailing edge High Leading edge Low Pulse width Pulse characteristic from a databus Rise time 50% 5 V Pulse amplitude (10 volts) 90% 9 V 10% 1 V Fall time Input = 1 (High) Output = 0 (Low) A X B A B A B C D Input Output High Low High the same components as found in the small-scale design but in larger numbers ranging from 12 to 100. The medium- scale designs are house circuits that are more complex, such as encoders, decoders, registers, counters, multiplexers, smaller memories, and arithmetic circuits. [Figure 12-268] The large-scale integrated circuits contain even more logic gates, larger memories than the medium-scale circuits, and in some cases microprocessors.
Microprocessors The microprocessor is a device that can be programmed to perform arithmetic and logical operations and other functions in a preordered sequence. The microprocessor is usually used as the central processing unit (CPU) in today’s computer systems when it is connected to other components, such as memory chips and input/output circuits. The basic arrangement and design of the circuits residing in the microprocessor is called the architecture.
DC Generators
Theory of Operation In the study of alternating current, basic generator principles were introduced to explain the generation of an AC voltage by a coil rotating in a magnetic field. Since this is the basis for all generator operation, it is necessary to review the principles of generation of electrical energy. When lines of magnetic force are cut by a conductor passing through them, voltage is induced in the conductor. The strength of the induced voltage is dependent upon the speed of the conductor and the strength of the magnetic field. If the ends of the conductor are connected to form a complete circuit, a current is induced in the conductor. The conductor and the magnetic field make up an elementary generator.
This simple generator is illustrated in Figure 12-269 , together with the components of an external generator 12-124 Ahrs +28 vdc Ahrs +28 vdc A/p controller +28 vdc Pitch servo valid +28 Roll servo valid +28 Yaw damper valid +28 Trim servo valid +28 Attitude valid +28 Heading valid +28 Attitude/heading reference system (Ahrs) Autopilot computer (engage circuit) Autopilot controller Pitch wheel centered Turn knob centered When all input circuits are valid, then the a/p can be engaged Autopilot Engage Logic +28 vdc OR gate input/output Truth table A f = A + B B A 0 1 0 1 B 0 1 f 0 1 A B + − A B + − circuit which collect and use the energy produced by the simple generator. The loop of wire [Figure 12-269A and B] is arranged to rotate in a magnetic field. When the plane of the loop of wire is parallel to the magnetic lines of force, the voltage induced in the loop causes a current to flow in the direction indicated by the arrows in Figure 12-269. The voltage induced at this position is maximum, since the wires are cutting the lines of force at right angles, thus cutting more lines of force per second than in any other position relative to the magnetic field. As the loop approaches the vertical position shown in Figure 12-270 , the induced voltage decreases because both sides of the loop (A and B) are approximately parallel to the lines of force and the rate of cutting is reduced. When the loop is vertical, no lines of force are cut since the wires are momentarily traveling parallel to the magnetic lines of force, and there is no induced voltage. As the rotation of the loop continues, the number of lines of force cut increases until the loop has rotated an additional 90° to a horizontal plane. As shown in Figure 12-271, the number of lines of force cut and the induced voltage once again are maximum. The direction of cutting, however, is in the opposite direction to that occurring in Figures 12-269 and 12-270, so the direction (polarity) of the induced voltage is reversed. As rotation of the loop continues, the number of lines of force having been cut again decreases, and the induced voltage becomes zero at the position shown in Figure 12-272, since the wires A and B are again parallel to the magnetic lines of force.
If the voltage induced throughout the entire 360° of rotation