Friday, June 15, 2018

Design Notes - Analog and Opamps - 01

Analog is the first thing in electronics. Valve Radios had Amplifiers and RF sections that were analog. Even the first computing methods are analog. Analog is close to Real Life parameter behavior. 

LM335 and LM336 -

LM335 is a temp sensor, LM335 . use it for temp for CJC. Temperature Sensors - RTDs and Thermocouples in  Temperature Measurement.

LM336-2.5 is an voltage Reference. precision 2.5V shunt regulator diodes, Applied as a precision 2.5V low voltage reference for digital voltmeters, power supplies or in opamp signal conditioning.

Current Loop -

4-20 ma will drive DC drives, motors and steam valves. It is a current loop, for long distance transmission, current loop is not prone to noise and hum, EMI RFI. As it is a small power transmission no loss of data, also many equipments can be in one data loop. A single transmitter with 4-20mA out can drive a strip-chart recorder, motor, controller and SCADA input. all in a series loop. Current loop is like 4-20 mA

Opamp Notes and Types
  • TL062, LF353, TL072, fet input. 1 tera ohm input imp.
  • OP07 higher price, 1 giga ohm. 75uV offset.
  • LF353 pin to pin replacement of TL062-72 and 82.
  • LM358 works on single supply too, low price, inp imp 1 meg.
  • LM324 Quad, works of batteries well.
  • All work best with dual +/- 5 V or more. LM7805 -LM 7905.
Analog Electronics: Basic Circuits of Operational Amplifiers

Examine the operation of the following circuits of operational amplifiers: inverting amplifier, summing amplifier, difference amplifier, differentiator, and integrator.

Remembering Bob Pease

Remembering Bob Pease

Points to Note -
  • Analog ground (opamps), digital ground (CMOS) and power ground (relays and LED) should be separate, (linked at root)
  • Glass epoxy PCB have high insulation resistance, above 10 tera ohms, and are not hygroscopic which means they do not drink water vapor, this makes them very suitable for precision instrumentation and sensitive circuits.
  • When you measure DC levels in 16bit accuracy or more you need resistors which have temp. coeff. of 10ppm, or you may have to put the entire circuit in a stable 45 deg oven. Thermoelectric effects, EMI, RFI, pA Leakage currents, ground loops, contact resistance all can make the readings drift and unusable.
  • High impedance points of circuit like 500 kilo ohm and above can pick up AC noise and DC leakage currents. this will affect the performance of circuit, so for DC you have to put a guard ring of the signal ground around that point in PCB. For RF you have to shield with things related to iron and mu metal, for low signals even a copper shield will do.
  • Percentage and ppm: when percentage becomes like 0.001% it is difficult to manage, so we use ppm-parts per million.5% means 5 parts in 100 parts. 23 ppm means 23 parts per million parts. 0.001% - shift the dp-decimal point four places to right it is 10ppm. 0.01% is 100ppm which is the variation of value of mfr resistors on temperature change.
Learn this at my Industrial Process Control Circuits

Thursday, June 14, 2018

Lightning Bolt damages Components

A ThunderBolt Zap can damage electronic parts. The Earth Leakage Circuit Breaker ELCB or Overload Breaker may Trip.

Surge Protection and Lightning Arrestors

Mains Strip Board should have protection, The EMI RFI filter, Varistors can help. Earthing and Lightning Arrestors should be good in the building.

The Blue ones are MOV Metal Oxide Varistors, sometimes they fail as a short circuit, so better to use a fast blow fuse. Then you see Gas Tube Arrestors that are even used in a Landline Terminal Box.

Surge Arrestors

A Surge Arrester is a device to protect electrical equipment from over-voltage transients caused by external (lightning) or internal (switching) events. Also called a surge protection device (SPD) or transient voltage surge suppressor (TVSS),

Line-Filter - A special class of capacitor is used in power-line (mains) filters.  Line filtering is a very tough application for a capacitor.

Achieving EMC for Dc-Dc Convertors - DC-DC converters, whether they be an off the shelf brick design or a discrete equivalent, are a source of EMI (Electromagnetic Interference). EMI is unwanted electromagnetic energy that propagates by radiation and conduction over system signal and power lines.

SMPS switch mode power supply design, PSpice simulation - These definitions should be considered relevant to a SMPS, and may not apply identically to other technical areas.

Friday, May 11, 2018

Instrumentation and Automation - 01

Here are some Test and measurement notes. These ideas come from practical experience. But the jots are not in any order but are quite important.

DuMont Lab Oscilloscope

Scope Notes
  • If the waveform on the scope droops then you may need to use a 10X attenuating probe or mode. this attenuator is at the tip of the probe hence better measurement possible, also very high frequency signals may be best transmitted over a 50 ohm impedance matched line to the Oscilloscope. 
  • Karl Ferdinand Braun - In 1897 he built the first cathode-ray tube...oscilloscope. CRT technology is to this day used by most television sets and computer monitors. The CRT is still called the "Braun tube".
  • Do not use an oscilloscope to measure 230V directly, use a transformer, differential probe or attenuator.
  • An oscilloscope 1M probe or a DMM 10M impedance can load circuits with nano-pico amps of bias.

DMM Notes
  • Test a NPN transistor, DMM in 200K range. emitter negative probe, collector positive probe, it should show open. while still holding that way press wet finger on base and collector, it may show some reading, then it is ok. for PNP swap probes polarity and do the same thing. the wet finger when pressed applies a base current in uA.
  • The most common reason of DMM failure is when a person tries to measure 230V AC with a DMM in current or ohms mode, with the probes in the wrong sockets. Use external attenuators and shunts.
  • A DMM in diode mode or resistance mode can be used to test IR diodes, take it under 100W lamp and measure, cover the IR diode and measure you will see a response in proper polarity.
  • If you put the DMM in 2V mode and measure the voltage across a ordinary LED near a 40W lamp you will see around 200mV. Turn off 40W lamp the mV will fall near 0. Even metal-can transistors with their top ground away will become photo sensors.
  • When you measure low voltages or high resistance like 1M with a DMM your body must not be in contact with the probe tips. Body resistance is low in comparison so error in reading or loading of mV from sensor, in sensitive and high impedance ranges.
  • Red socket and probe for positive and black socket and probe for negative
  • Is it oscillating ?.... We cannot say, it could also be DC, you need to see if a Clock is present. use a signal tracer or a DMM freq mode, or AC measurement. or build this solorb.com-elect-logprobe. When you do not have a scope you can build one for the PC.
  • Polarity and Zero Cross indicators tell you to swap the leads. Use a comparator or opamp to build it.

Contents

Basic Electronics
Basics of Electronics
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Testing Points
Learning Electronics
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Production Notes
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Library
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Socratic Electronics
Blobz Guide Electric Circuits


Product Design
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Constant Current Source
Good Voltage Regulators
Insulation Resistance
Digital Insulation Tester
DN Schematic PCB 04
DN Product Design 07


Hobby Circuits
VU Meter Circuits
LED brightness control
555 Incredible Chip
Process Control
liquid level measurement
Thermocouples and RTD
Design ADC Interface uC
Thermocouple Amplifier
IA Instrumentation 02
Temperature on DMM
Optical Proximity Switch
Analog Mux - Data Acquisition


Test Measurement
Instrumentation Automation
NI Test and Measurement
DMM Digital Multi Meter
Oscilloscope in T&M
IA Automation 01
Build Instruments
Tektronix T&M Equipment
Educators Corner – Agilent


Power Electronics
UPS Background
Transformer Connections
DN Power Electronics 03
DN Power Electronics 02
Half Bridge Convertor SG3525


Embedded
Interfacing Microcontrollers
Embedded Process Control
80C31 8052 Microcontroller
Microprocessors and uC
Embedded Systems Design

Components
Good Voltage Regulators
Relays and Contactors
Potentiometers Trimpots
Prototype Boards Types
Types of Capacitors
Types of Switches
Resistors How they Work
Coils Transformers SMPS
Mains Transformers Types
DN Components Selection 05

Tutor Gadgets
Count-Up Timer
Digital Logic Gates
Electronics Tutors

History
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Charles Proteus Steinmetz
Muntzing a Circuit Design
Teralab Electronics projects
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Tables, Charts, Videos
Binary and Hex
Resistor Color Code
Ohms Law
Giga, Tera, Pico, Nano
High Resistance Materials

Analog
School - Analog Design
DN Analog Basics 06
DN Op-Amps 01
TI Semiconductors

Practical Electronics

Practical Electronics
Basic Electronics, EE Reference Resource, Analog, Digital, Power and Electrical.

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