Electronic Systems and Design

Branch of electronics in charge with the manufacture of heavy-duty electronics for industrial uses

“Thyratron” “Transitor”

Acts as a bistable switch, takes high voltages

Silicon Controlled Rectifier / semiconductor-controlled rectifier

4-layer solid-state current-controlling device used in electronic devices that require control of high voltage and power

schematic diagram of SCRs

A graphical representation showing the electrical connections and functions of silicon controlled rectifiers in a circuit, including their input and output terminals.

Forward Blocking region

Operational state of an SCR where it is reverse-biased and does not conduct current despite the presence of a forward voltage, allowing the device to block current flow.

Reverse Blocking Region

Forward Conducting Region

The operational state of an SCR where the device is forward-biased and conducts current, allowing significant current to flow through the device while it remains in the conducting state.

SCR Characteristic Curve

A graph representing the current and voltage characteristics of a Silicon Controlled Rectifier (SCR) across its various operational regions, including forward blocking, reverse blocking, and forward conducting.

Turning Off SCR methods

1. Anode Current Interruption

2. Forced Commutation

Anode Current Interruption

process of reducing the current flowing through the anode of a thyristor (SCR) to below its holding current

Series Interruption

Normally closed configuration of Anode Current Interruption

Shunt Interruption

Normally open configuration of Anode Current Interruption

Forced Commutation

process of turning OFF a Silicon Controlled Rectifier (SCR) in a DC circuit by using an external circuit (using capacitors, inductors, auxiliary SCRs, or switches) to force the anode current to zero or below the holding current

Firing angle

angle measured from the zero-crossing of the AC voltage to the instant an SCR (Silicon Controlled Rectifier) is triggered ON by a gate pulse.

In an AC circuit, the voltage is sinusoidal. Even though the SCR becomes forward-biased at the beginning of each positive half-cycle, it does not conduct immediately. It starts conducting only when a gate pulse is applied.

dv/dt Triggering Method

• The SCR is forward-biased but OFF.

• The anode-to-cathode voltage rises very rapidly (high dv/dtdv/dtdv/dt).

• The SCR's internal junction capacitance charges, producing a charging current.

• If the charging current is large enough, it acts like a gate current.

• The SCR turns ON without a gate pulse (unwanted triggering).

Temperature Triggering Method

unintentional turning ON of a Silicon Controlled Rectifier (SCR) due to a high junction temperature, even without applying a gate pulse.

As the SCR's temperature increases:

• More electron-hole pairs are generated inside the semiconductor.

• The leakage current across the SCR increases.

• If the leakage current becomes large enough, it acts like a gate current.

• The SCR turns ON without any gate signal

Forward voltage triggering method

process of turning ON an SCR by increasing the forward anode-to-cathode voltage until it reaches the breakover voltage (VBO), even without applying a gate pulse.

Snubber circuit (RC snubber)

used to protect an SCR from unwanted dv/dt triggering.

low firing angle value

output of SCR is increased, turning on is faster

high firing angle value

output of SCR is decreased, turning on is slower

Latching Current (IL)

The minimum anode current required immediately after triggering to keep the SCR ON when the gate signal is removed.

Holding Current (IH)

minimum anode current required to keep the SCR conducting. If the current drops below this, the SCR turns OFF.

SSSGDT

4-pin device which is an SCR plus another external terminal, connected to the base of the top resistor and the collector of the bottom transistor
Used for faster switching time

Schematic diagram of SCS

schematic symbol of GTO

Shockley Diode / Latching Diode

The device is turned on using the Forward Breakover Voltage

Schematic symbol of Shockley Diode

DIAC

Shockley diode that is back-to-back
It is a full-wave or bi-directional semiconductor switch that can be turned on in both forward and reverse polarities

DIAC characteristic curve

Schematic symbol of DIAC

5 - 30us

Typical turn off time of SCR in Forced Commutation

Typical Breakover Voltage of DIAC

20-40V

Typical Breakover Current of DIAC

50 - 200uA

TRIAC

SCR that is back-to-back

Schematic symbol of TRIAC

TRIAC characteristic curve

Apply a negative pulse to CG or a positive pulse to AG

Quadrant IV (MT2 negative, gate positive)

Household light dimmer switches

Most common real-world application for a TRAIC and DIAC combination circuit

DIAC are specifically designed to trigger

TRIAC and SCR
saka lang matrigger yung DIAC if naabot na ang time constant RC

% derating of thyristor

means you do not use the thyristor at its full rated current. Instead, you use only (100% - % derating) of its rated current for safe operation.

number of thyristors required formula

D - derating
IL - load/circuit current rating

PIV (Peak Inverse Voltage)

maximum reverse voltage that a diode, SCR, or thyristor can withstand in the OFF state without breaking down

PIV formula for Half-wave and Bridge rectifier/SCR/thyristor

PIV formula for Full-wave

Field of electronics that deals with the generation, detection and control of light using electronic devices, particularly semiconductors.
Converts electricity to light and vise versa

two-lead semiconductor devices that are similar to normal diodes except that they emit light that can be visible, infrared, or ultraviolet.

LED schematic symbol

Characteristics of GaAs LED

Characteristics of GaAsP LED lower Vf

Characteristics of GaAsP LED higher Vf

Characteristics of GaAsPN LED

Characteristics of AlGaP LED

Characteristics of SiC LED

Characteristics of GalnN LED

injection laser or diode laser

semiconductor device that emits coherent light when an electrical current is passed through it.

LASER meaning

Light Amplification by Stimulated Emission of Radiation

Coherent light emitted by LASER

Monochromatic (same wavelength), same phase, same time

Photoresistors / light dependent resistors (LDRs)

electronic component whose resistance changes depending on the amount of light falling on its surface.
@ dark = resistance is high
@ illumination = resistance drops

Photoresistors / light dependent resistors (LDRs) schematic symbol

Photodiodes

two-lead semiconductor devices that convert light energy (i.e., photons) directly into electric current
constructed using a very thin n-type semiconductor together with a thicker p-type semiconductor.

Photodiodes schematic diagram

Phototransistors

a type of transistor that operates by using light to control the flow of current between its emitter and collector
It's a semiconductor device that converts light signals into amplified electrical signals.

Solar Cells

These are simply photodiodes with exceptionally large surface areas.
These larger areas allow the them to be more sensitive to incoming light as well as more powerful, in terms of both voltage and current, than photodiodes.
Commonly used in solar panels, but they are also often used as light-sensitive elements in detectors of visible light.

Optoisolator / optocoupler / photocoupler,

an electronic component that transfers electrical signals between two circuits using light.
It provides electrical isolation, meaning it prevents direct electrical connection between the circuits while still allowing signal transfer.
LED + phototransitor

Optoisolator / optocoupler / photocoupler schematic symbol

@Rayleigh Scattering, ↑frequency = ↑attenuation. So with infrared with less f then lower loss

Transducers

• Devices that convert one form of an energy to another.
- They also convert non-electrical quantity to an electrical form.

• Categories include resistive, capacitive, inductive, piezoelectric, optical, and digital transducers.

Range [Selection of Transducers]

Should be large enough to encompass all the expected magnitude of the measured (measuring range covers every value you expect to measure.)

Sensitivity [Selection of Transducers]

should give a sufficient output signal per unit of measured input to yield meaningful data.

Sensors

Converts any energy into electrical signal

Actuators

Converts electrical energy into any energy

Electrical output characteristics [Selection of Transducers]

(e.g. the output impendence, frequency response and response time) of the output signal should be compatible with the recording devices and the rest of the measuring system equipment.

Physical environment [Selection of Transducers]

Should be able to withstand the environment conditions to which it is likely to be subjected while carrying out measurements and test.

Thermocouples

a temperature sensor that generates a voltage based on the temperature difference between two dissimilar metal wires joined together.

Thermistor schematic symbol

Thermistor

a type of variable resistor whose resistance changes significantly with temperature.
These devices are commonly used for temperature sensing and control in various applications.

Plezoelectric crystal microphone

an active transducer that generates its own electrical output without needing an external battery

Seebeck Effect

A thermocouple is a temperature transducer made by joining two different metals. It operates based on this, which generates a tiny voltage proportional to the temperature difference between the junctions.

Negative Temperature Coefficient (NTC) thermistor

temperature increases, decrease resistance

resolution of a transducer

The smallest detectable change in the Input that causes change in the output

Crowbar

A circuit that protects a sensitive circuit from a sudden increase in supply voltage

Programmable Logic Controllers

is a special form of microprocessor-based controller that uses a programmable memory to store instructions and is designed to be operated by engineers with perhaps a limited knowledge of computers and computing languages.

ladder programs

pre-programmed programmable logic controllers so that the control program can be entered using a simple pictorial form of language

Five Basic Components of PLC

Central Processing Unit CPU

unit containing the microprocessor and this interprets the input signals and carries out the control actions, according to the program stored in its memory, communicating the decisions as action signals to the outputs.

Power Supply

needed to convert the mains a.c. voltage to the low d.c. voltage (5 V) necessary for the processor and the circuits in the input and output interface modules.

Programming Device

used to enter the required program into the memory of the processor.
The program is developed in the device and then transferred to the memory unit of the PLC.

Memory Unit

where the program is stored that is to be used for the control actions to be exercised by the microprocessor

Input/Output Section

where the processor receives information from external devices and communicates information to external devices.
The inputs might be from switches, temperature sensors, or flow sensors, etc. combined with appropriate signal processing elements.
The outputs might be to motor starter coils, solenoid valves, etc.

Counter

If you want a conveyor belt to stop exactly 10 seconds after a box passes a sensor, what basic instruction do you add to the program?

Scan cycle

process in which a PLC continuously reads input signals, executes the control program, and updates the output signals in a cyclical manner

Sequential logic control

primary application of Programmable Logic Controllers (PLCs) in industrial automation

UJT Unijunction Transistor

• non-linear amplifiers so it is used as switch

• known for negative resistance since RB1 is decreasing overtime

• intrinsic stand-off ratio is non-changing