Electrical4U 
A logic gate is a digital circuit whose output follows a Boolean function of its inputs. Earlier pages covered the internals of digital logic gates. This page covers common applications of logic gates that follow from that truth table. OR combines trips. AND acts as an enable or inhibit. XOR and XNOR handle parity. NOT … Read more
There are two common AC systems in electric circuits: single-phase and three-phase. In a single-phase circuit, current flows out on one live conductor and back on the neutral, so the power that can be sent is limited. Both generation and load can be single-phase, and that arrangement was used for a long time.Polyphase systems were … Read more
The three phase induction motor is an AC electrical motor built from a stator and a rotor. Plants use three phase induction motors for much of their shaft power because the construction is simple and rugged. There is no commutator. Slip keeps speed fairly steady with load. Power crosses the air gap from the stator … Read more
What is a Single Phase Induction Motor? A single phase induction motor is an asynchronous AC motor fed from a single-phase supply. Homes and shops use single-phase more than a three phase system because the wiring is cheaper for modest loads. Industry still uses three-phase for larger shaft power. The motor itself is simple to … Read more
Single-phase induction motors are not self-starting from the main winding alone. An extra flux, from an auxiliary winding or a shaded pole, is used to start them. They are classed by how that extra flux is produced: Split Phase Induction Motor Besides the main winding, the stator of a single-phase induction motor has an auxiliary … Read more
A Kelvin Bridge (Kelvin double bridge) measures low resistance by adding extra ratio arms so lead and contact resistance do not swamp the unknown. A Wheatstone bridge is the usual tool for medium resistance; a well-built one can reach about 0.1% on those values, not on milliohm samples. Textbooks group electrical resistance into three bands … Read more
Excess 3 Code This page is about BCD addition and subtraction with Excess 3 code. Excess 3 code stores each decimal digit as the 4-bit binary of that digit plus 3 (0 is 0011, 9 is 1100). For any binary number already grouped as BCD digits, add 0011 to each group to form Excess-3, then … Read more
Error detection and correction codes add extra bits so a receiver can see whether a digital word was changed in transit, and in some codes restore the original bits. Analog and digital links both pick up errors; a computer or a comms link needs a definite check because one wrong bit can change a code. … Read more
Fan-out in digital electronics is the number of same-family gate inputs that one logic-gate output can drive without leaving the valid logic levels. One output can feed several inputs, but only up to that count.The limit is set by how much current the output can source at a high level and how much current it … Read more
TTL means Transistor Transistor Logic, a bipolar digital family built from NPN transistors, PN junction diodes and diffused resistors. The usual gate is a NAND gate. Subfamilies include standard 74, low-power 74L, high-power 74H, Schottky 74S plus later LS, ALS and 74F parts. The sections below cover the inner circuit of the main groups. Standard … Read more