Electrical and electronical training



Electrical and electronical training

I. Basics of electrics

Connection of electrical switches, electrical bulbs, circuit breaker, staircase switches, contactors. This part will include connection of an AC 3-phase motor with frequency changer.

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Fig. 1: Connection of training stand

During interconnection of power electronics an attention has to be taken to three types of wires PE, N and L. The circuitry in buildings have to be divided at least into two circuits: lights and electrical sockets – each circuitry has its own circuit breaker.

Sockets are connected according to Fig. 2 with hot wire always on the left.

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Fig. 2: Conection of electrical socket and staircase switch

Screw terminal is used to divide the wires (neutral, ground and hot) into several branches. In screw terminals the yellow pads are used for ground wires.

Special circuitry is for motors (asynchronous or induction motors) or other high power equipment. Special attention has to be taken with motor label – the most important is connection type (delta or start) with according voltages and currents, power in kW, revolutions per minute and power factor. These values are input for frequency changer. The revolutions are slightly less than calculated from frequency (optimal frequency is usually 50 Hz). For example 50x60=3000 revolutions so the real frequency can be 2850 Hz, or for motor with division factor 2 or 3 (number of magnetic poles) it can be 1430 Hz or 970 Hz. Optimal operation is when motor is operated with nominal (50 Hz) frequency. The frequency cannot drop very low since the cooling air flow cannot efficiently cool the motor (typically no less than 20 Hz). The frequency from frequency changer is usually between 35 – 65 Hz. There are other important parameters in frequency changer – for example Ramp (how fast the motor should start or stop to operate).

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Fig. 3: Motor label and motor unit

3-phase connection: star (higher voltage) or delta (lower voltage) on motor – Fig. 4.

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Fig. 4. : Connection of delta and star for 3-phase motors

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Fig. 5: Frequency changer and graph showing optimal frequency

II. Basics of electronics

Connection of parallel and in series resistors (Fig. 6) – OR and AND functionality (LED connection with resistors), connection of potentiometer and buttons. Typical LED (LED is a diode – longer contact is +) has a voltage drop of 1,8 V, the current which is required through LED is typically 10 mA – hence from V = R.I (ohm law) a needed resistor can be calculated.

Measurement 1 (parallel and in series connection): 9V battery, 2x LED (identical), 1x 680ohm (Ω) – measure voltages and currents.

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Fig. 6: Parallel and in series connection

Multimeter and measurement of voltage, current, resistance, diodes, (capacitors and J, K or Pt100 thermocouples for better multimeters) – Fig. 7.

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Fig. 7: Measurement of voltage and current

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Fig. 8: Resistor color code

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Fig. 9: Connection of button and voltage divider

Measurement 2 (button and potentiometer as a voltage divider): 9V battery, 2x LED, 1x 680ohm, 1x button, 1x potentiometer (2k5). Fig. 9.

Measurement 3 (photoresistor): same as Measurement 2 but instead of 680 ohm resistor use photoresistor. Fig. 10.

Measurement 4 (diode): same as Measurement 2 but in series with 680 ohm put diode in both directions.

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Fig. 10: Schematic for photoresistor, diode and capacitor – with electrolytic capacitors a special care has to be taken about polarity

Capacitors have also something like a color coding of resistors but only using a special codes for certain values - (e.g. 103 means 10x103pF=10nF). Basically electrolytic capacitors are cylindrical.

Measurement 5 (tyristor): 9V battery, LED, 680 ohm, 220 ohm, 1k ohm, 2x button, tyristor (cathode is -, anode is +)

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Fig. 11: Description of TIC106 and diagram for tyristor control

Transistor is a device with two PN junctions. Basically there are bipolar junction transistors (BJT) and Field effect transistors (FET). For NPN transistors the negative connector is called emittor (or source for FET), the posive connector is called collector (or drain for FET) and the controlling conector is called base (or gate for FET). It can be used to build various circuits – for example amplifiers of flip-flops (basis for logic circuits).

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Fig. 12: Schematic of transistors

Measurement 6 (basic astable circuit): 2x 3,3 uF, 2x 680 ohm, 2x 820k ohm, 2x 470k ohm, 2x 680k ohm, 2x NPN transistors. R2 and R3 transistors can be varied either only 470k ohm (higher frequency), or in series 820kohm and 680kohm (lower frequency). The frequency can be computed using f = k/(0,69C1R3+0,69C2R2) (where k is in our case approx. 2). For C1=C2 and R2=R3 there are precomputed values of frequencies – Fig. 13, Fig. 14 and Fig. 15.

Assume that transistor, TR1 has just switched “OFF” (cut-off) and its collector voltage is rising towards Vcc, meanwhile transistor TR2 has just turned “ON”. Plate “A” of capacitor C1 is also rising towards the +9 volts supply rail of Vcc as it is connected to the collector of TR1 which is now cut-off. Since TR1 is in cut-off, it conducts no current so there is no volt drop across load resistor R1.

The other side of capacitor, C1, plate “B”, is connected to the base terminal of transistor TR2 and at 0.6v because transistor TR2 is conducting (saturation). Therefore, capacitor C1 has a potential difference of +5.4 volts across its plates, (6.0 – 0.6v) from point A to point B.

Since TR2 is fully-on, capacitor C2 starts to charge up through resistor R2 towards Vcc. When the voltage across capacitor C2 rises to more than 0.6V, it biases transistor TR1 into conduction and into saturation.

The instant that transistor, TR1 switches “ON”, plate “A” of the capacitor which was originally at Vcc potential, immediately falls to 0.6 volts. This rapid fall of voltage on plate “A” causes an equal and instantaneous fall in voltage on plate “B” therefore plate “B” of C1 is pulled down to -8.4V (a reverse charge) and this negative voltage swing is applied the base of TR2 turning it hard “OFF”. One unstable state.

Transistor TR2 is driven into cut-off so capacitor C1 now begins to charge in the opposite direction via resistor R3 which is also connected to the +9 volts supply rail, Vcc. Thus the base of transistor TR2 is now moving upwards in a positive direction towards Vcc with a time constant equal to the C1 x R3 combination.

However, it never reaches the value of Vcc because as soon as it gets to 0.6 volts positive, transistor TR2 turns fully “ON” into saturation. This action starts the whole process over again but now with capacitor C2 taking the base of transistor TR1 to -8.4v while charging up via resistor R2 and entering the second unstable state.

Then we can see that the circuit alternates between one unstable state in which transistor TR1 is “OFF” and transistor TR2 is “ON”, and a second unstable in which TR1 is “ON” and TR2 is “OFF” at a rate determined by the RC values. This process will repeat itself over and over again as long as the supply voltage is present.

The amplitude of the output waveform is approximately the same as the supply voltage, Vcc with the time period of each switching state determined by the time constant of the RC networks connected across the base terminals of the transistors. As the transistors are switching both “ON” and “OFF”, the output at either collector will be a square wave with slightly rounded corners because of the current which charges the capacitors.

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Fig. 13: Connection of astable multivibrator circuit

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Fig. 14: Table of frequencies for R and C

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Fig. 15: RC discharging circuit with time constant T=RC, at 5T the capacitor is fully discharged

Measurement 7 (transistor as an amplifier): 1kohm, 47kohm, button, NPN transistor, 2x LED

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Fig. 16:Circuit of amplifier with transistor

Measurement 8 (operational amplifier non-inverting): 9V battery, 6k8, 2x 480, 220, LM741, potentiometer

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Measurement 9 (operational amplifier inverting): 9V battery, 6k8, 2x 180, 1k5, 2x 12k, LM741, potentiometer

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Fig. 17:Circuit of amplifier with transistor

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Fig. 18: Inverting amplifier, non-inverting amplifier and voltage follower

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Fig. 19: Connection of DIP 741 transistor, aside from DIP package there is also SMD especially for soldering

Measurement 10 (Pulse width modulation): buzzer, Arduino kit (PWM to pin 3, possibility to change PWM from 0 to 255).

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Fig. 20: PWM example

PWM is very often used for controlling of power going to a specific device.

Functionality of diodes, transistors (NPN – BC547B and PNP – BC556B) as amplifiers, operational amplifiers (741, AD620) as voltage followers and amplifiers, photoresistors, tyristors (TIC106M), voltage stabilizer (5V – LM7805, 6V – LM7806), relay.

Measurement 11 (relay with soldering): relay, board, 1k5 (or 2k2), LED, 9V battery

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Fig. 21: Connection of relay

Measurement 12 (LM7805 voltage stabilizer): 2x 3.3uF, LM7805, diode 1N4007, 9V battery

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Fig. 22: Voltage stabilizer

Voltage stabilizer can be done with a Zener diode (diode operating in a reverse direction

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Fig. 23: Zener diode, notice the change in scale for positive and negative voltages

Measurement 13 (phototransistor detection of movement): 2x 1k5 (or 1k2), UV diode, phototransistor (resistors on +)

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Fig. 24: OWON SDS6062V - osciloscope, CEM DT-101 - multimeter, SOLOMON SL-976 – soldering station

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Fig. 25: Connection of buzzer with two transistors

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Fig. 26: 555 timer IC (integrated circuit) with amplifier

Measurement 14 (timer 555): 9V battery, 1k2 (R1), 12k (R2), 100uF, 150ohm, LED, 10nF, 555, C 100uF or 100nF with inductance – functionality of osciloscope

Measurement 15 (timer 555 - monostable): 9V battery, LED, 10nF, 150ohm

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III. Basics of processor programming

Arduino UNO with connection to PC (temperature sensor TMP36, display 1637, buzzer).

The most common communication interfaces are serial, I2C and SPI. For serial (COM, UART) communication it is necessary to define several parameters (default> COM number: COM1, baud rate: 9600, data size: 8, parity: none, handshake: OFF).

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Fig. 27: COM port (RS 232)

Measurement 16 (state machine with Arduino and COM communication): Arduino, 2x LED, 2x resistor, PC terminal - Hercules, (possible show of closed loop)

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Fig. 28: Simple state machine with serial communication

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Fig. 29: Arduino UNO, display (TM1637) and stepper drive (ULN2003)

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Fig. 29a: Connection of LM35 thermometer

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Fig. 30: Pinout of Arduino Uno and configuration of type UNO and Port number

Measurement 17 (display TM1637): display, Arduino

Measurement 18 (display TM1637 with temperature sensor): display, Arduino, temperature sensor

#include

const int CLK = 9; //Set the CLK pin connection to the display

const int DIO = 8; //Set the DIO pin connection to the display

int NumStep = 0; //Variable to interate

TM1637Display display(CLK, DIO); //set up the 4-Digit Display.

void setup()

{

display.setBrightness(0x0a); //set the diplay to maximum brightness

}

void loop()

{

for(NumStep = 0; NumStep < 9999; NumStep++) //Interrate NumStep

{

display.showNumberDec(NumStep); //Display the Variable value;

delay(500); //A half second delay between steps.

}

}

Stepper motor - functionality

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Fig. 31: Unipolar and bipolar stepper motor

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Fig. 32: Stepping modes (driving only one winding, two windings and half-step)

Measurement 19 (driving stepper motor ULN2003): stepper motor, Arduino

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Fig. 33: Connection of stepper motor

IV. Basics of PLC

Measurement 20 (creating of ETH cable): cable, connectors, crimping pliers

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Fig. 34: Connection of standard Ethernet

Tecomat Foxtrot 1004 (8DI (4AI), 6DO - ) programming using Mosaic. Creating of state machine, connection to Arduino with temperature sensor and stepper drive). Web server on PLC.

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Fig. 35: Tecomat Foxtrot and programming ladder diagram

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Fig. 36: Layout for PLC training

Mosaic – PLC programming

After a double click on Mosaic icon a screen with Hardware key required appears. If you have only one or two modules of Tecomat you do not need a key otherwise you need to buy a professional licence.

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Under File -> New -> New project group create a new Project group under a default Mosaic directory (c:\MosaicApp\).

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Then enter the name of new project – then choose modular system Foxtrot.

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Choose program name and select programming language LD (ladder).

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Choose program instance name and FreeWheeling.

Under Project manager – HW configuration – double click on CPU type and choose appropriate.

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Under PLC Address: 0 choose appropriate connection to PLC. If you do not have PLC you can choose Simulated. If you have PLC you can connect it by e.g. Ethernet, choose appropriate connection and click Connect. Then you can close Project explorer. In the top of the window two small windows appear: one with 0:Halt and the other one with ms (typically 110ms).

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Under Icon IO give aliases to inputs and outputs.

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After clicking to a chosen block red and blue squares appear in the ladder diagram. When clicking on blue it means a parallel connection, when clicking on red it means in series connection.

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After placing the block a dialog appears. Here it is necessary to click on icon with … and then continue with a tab Global and under VAR_GLOBAL are our inputs and outputs.

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When placing a timer it is necessary first to choose General Block and then under Counter/Timer choose TON with some name. Then as an operand we have to enter T#1000 in order to have 1000ms delay (an example).

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If you want to program PLC just choose Program – Compile.

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A message with possible errors appears. If everything is OK there are no errors.

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Now you can choose under PLC – Run. You have to confirm to send the code to PLC and choose e.g. Restart type Cold.

Two small windows in the top of the window change slightly.

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It means that the program is running. With right click on a particular variable you can choose to add the watch and in the bottom of the window under the tab Watch you can see all your watches. Under I/O Settings you can modify value of a particular variable and immediately see the result under Watch tab and also in ladder diagram.

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To stop debugging you can choose PLC – Halt.

V. Labview with camera

Possible demonstration of programming Labview environment with camera and image processing.

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Fig. 37: Labview camera programming

VI. PC Schematic for drawing of electrical connections

Start with File-New-Project(Template)-PCSstart

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Fig. 38: Start new Project from template

Give it a name and a customer.

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Fig. 39: Routing enabled

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Fig. 40: Different types of pages: Diagrams, Panel layout, Lists

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Fig. 41: Panel layout

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Fig. 42: Defining next available name for a part with question mark, updating Lists with Update the List

Drawings for electronic boards: Eagle ().

References:











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