1 Learning in Electronic CircuitsReading Schematics © 2013 Universitat Politècnica de Catalunya (EPSEVG) José Antonio Soria Pérez - Collaborative Professor at the EPSEVG (UPC). C/ V. Balaguer, 1. Vilanova i la G. (Barcelona - Spain). Telf: Fax: Office hours: VG3-D101 – EEL MON 10-14h, TUE: 10-14h (Yellow zone)

2 In this lesson you will learn...... to read schematics Definition of the different parts of a schematic Designation of components Annotation of electrical variables, magnitudes and units

3 The elements of “schematics”The “schematics“ represents the connection of components in a circuit A junction is any connecting point between two (or more) components A branch is any open path containing two or more junctions. A mesh is any closed path (clockwise convention) containing three (or more) junctions This point is a junction with 4 connected wires This point is a crossing of 2 unconnected wires 3 This is a junction A Specific branch Upper branch Lower branch Left branch Middle branch Right branch 1 2 In this schematic, the 7 components are connected with 6 junctions Several possibilities depending on chosen components This schematic has 3 meshes

4 The elements of “schematics”The “schematics“ represents the connection of components in a circuit A component consists of a symbol and a designator Components are generally annotated from left-to-right and up-to-bottom Example: A resistor Resistors + Capacitors Inductor Transformer Diodes Bipolar Transistors MOSFETs JFET DC Voltage AC Voltage DC/AC Current Variable controlled Passive: Semiconductor: Active: (value) R n (value) R n R Uppercase letter specifies component class n Subscript specifies component number (...of the same class in the diagram) Z2 (‘R’ stands for Resistor) Z5 (value) Component value (when inserted) This is the symbol of a resistor (i.e. 1kΩ) ATT = Atenuator BR = Bridge rectifier BTT = Battery C = Capacitor D = Diode (inc. Zeener, etc…) DS = Display F = Fuse J = Jack Connector JP = Jumper K = Relay L = Inductor LS = Loud speaker M = Motor MK = Microphone P= Potentiometer PS = Power supply Q= Transistor R = resistor RT = Thermistor S = Switch T = Transformer TC = Termocouple TR = Trimmer TP = Test point U = Integrated circuit V = Vaccum tube X= Transducer Y = Crystal or (oscillator) Typical Designation References ...and this its designator Z1 In semiconductors and integrated circuits, this label is a reference number specifying manufacturer information Z4 Z7 Example: A Zenner diode D1 Z3 Z6 BZ4V7 Silicum (B); Zenner diode (Z); Breakdown voltage 4.7 Volts Manufacturer’s reference number

5 The elements of “schematics”The “schematics“ represents the connection of components in a circuit A component consists of a symbol and a designator Electricity is generated by connecting external (or independent) sources Sources can be either Voltage (V) or Current (I) … ... and can be either Direct Current (static) or Alternate Current (dynamic) Uppercase and lowercase symbols specify static and dynamic behaviour In sources, the subscript specifies the nature of external energy Z1 Z2 Z3 Z4 Z5 Z6 Voltage source A DC voltage source An AC voltage source Current source VCC I + V t VCC vcc(t) + Uppercase symbol Lowercase + + VCC (12V) ICC (1A) CC.- Power supply IN.- Input source G.- Generator VCC _ _ In “active” sources, electric current normally flows from their POSITIVE pole to their NEGATIVE pole Uppercase symbols generally denote constant parameters Lowercase symbols generally denote incremental parameters Voltage and polarity fixed to the circuit DC values do not vary with the time AC values vary with the time Current and flow direction fixed to the circuit (Convention: Current outgoing from the positive pole) (Convention: Positive pole set by flow direction)

6 Annotation of electric signalsThe following notations are used both in DC and AC signals Electrical variables always in italic. Metric prefixes and main electrical units Total component (lowercase symbol, uppercase subscript) Vectors are indicated in bold iC(t) aka. iC Incremental (or AC) quantities (both lowercase) V → [Volts] → V I → [Ampers] → A P → [Watts] → W E → [Joule] → J R → [Ohms] → Ω C → [Farad] → F L → [Henry] → H Ic Peak value iC(t1) ic(t1) IC –Direct (or DC) quantities (both uppercase) t - time

7 The elements of “schematics”The “schematics“ represents the connection of components in a circuit A component consists of a symbol and a designator Electricity is generated by connecting external (or independent) sources Electric current flows through the circuit branches and causes voltage drops to appear “across” junctions. Convention with electric current always entering the positive pole i-v relationship established by component operation and electrical laws Z1 Z2 Z3 Z4 Z5 Z6 Example: The Resistor IZ1 IZ4 IZ6 = IZ4 IZ5 = IZ4 IZ3 VZ1 _ VZ4 + _ VCC + I + _ V The theme of obtaining circuit behaviour using “electric laws” is addressed in the next lesson: Lesson 2: Circuit Analysis VZ3 _ + VZ6 _ + + 𝑅 = 𝑉 𝐼 The Ohm’s Law * _ IZ2 VZ2 _ + VZ5 _ + The Ohm’s law is the most basic form of electric law (i-v relationtionship) in circuit analysis

8 Components, Variables and Annotation rulesThe “schematics“ represents the connection of components in a circuit A component consists of a symbol and a designator Electricity is generated by connecting external (or independent) sources Electric current flows through the circuit branches and causes voltage drops to appear “across” junctions. Circuit operation is seen as an Input /Output relation Electronic circuits (or “systems”) carry out operations with electric signals ”Ways” of representing the input and output of a circuit Input of the system Electronic System Output of the system Z1 Z2 Z3 Z4 Z5 Is the initial signal to be processed by the circuit + vs(t) Vin _ + Vout _ + ZL Is any electric variable providing the result It can be any External Source To get the result we often use a load (L) (another circuit device or component) Source/Load Full representation Arrow notation Dot notation

9 Components, Variables and Annotation rulesThe “schematics“ represents the connection of components in a circuit A component consists of a symbol and a designator Electricity is generated by connecting external (or independent) sources Electric current flows through the circuit branches and causes voltage drops to appear “across” junctions. Circuit operation is seen as an Input /Output relation The Ground is a reference point (typ. 0V) for other voltages in the circuit Other ground reference symbols: Z3 Z1 Z4 ZL Vout _ + Vin Z3 Z1 Z4 ZL Vin _ + Vout _ + Unipolar Input & output Differential Input & output Earth Ground Signal Chassis Generic These are equivalent circuits Generally (but not necessarily) assigned to negative poles in input sources Z2 Z5 Ground terminal Voltages refferred to (negative pole connected to) ground are known as unipolar voltages A variety of definitions depending on the true physical connection Voltages not refferred to ground are differential (or floating) voltages

10 1st. Exercise Annotate the following circuit: 1 6 4 2 5 3Place the ground connection and specify designators and electric variables (indicating voltage positive and negative poles, and electric current flow direction). Specify the total number of junctions and possible meshes of the circuit. Solution: 3 junctions 6 meshes I1 IR2 R2 I2 1 2 IR1 + _ VR2 IR3 + VR1 + _ VR3 + _ + 1 6 4 2 5 3 V1 R1 R3 V2 3 These are, in fact, the same junction

11 2nd. Exercise Annotate the circuitComplete the annotation just as in the preceding example specifying junctions and meshes (Note: Be aware of both AC and DC components) Solution: 5 junctions 8 meshes iR2 R1 R2 R3 R4 R5 iR5 iR4 iR3 iR1 + _ vR2 vR4 vR3 v2 vR5 vR1 + V1 i2