EE Tech Metrics - dapj: June 2009

Monday, June 15, 2009

Test Measurement and Test jigs

Test Tools are needed for Troubleshooting and Repairing Electronic Gadgets, Equipment, Electrical Panels and Machines. Precision Instruments are required for calibration of field and machine control electronics. These are also required by the R&D engineer for design and development of new products and trying out new concepts.

Test and Measurement

In Production testing, Production Engineering, Quality Assurance QA-QC etc. You need to build Test Jigs, Configure Automated Testing depending on the size of project or budget allocated; yet it has to be made flexible, scalable and modular. These require instruments or blocks that can be adapted and reconfigured or even interface with a computing network for automated testing, reporting and analysis.

Special Electronics come with every tool or gadget these days, A Slide calipers has a LCD display, Digital Readouts on mechanical instruments can help measure even sub-microns easily. Analytical and Chemical Instrumentation is another specialized niche. Then we have medical instrumentation which is more demanding in quality and requires sensors that are small, very sensitive and safe.

Instrumentation goes into all these and beyond. The day we find water on mars, It is only because of a precision instrument at the helm of things.

Digital and Logic Circuits Basics

Digital Logic :

Basic Digital Circuits

You can start learning digital circuits by learning the operation of logic gates, see an interactive gadget tutor Logic Gates.

Then you can test the basics with these tutor gadgets

Some Digital circuits i have explained Digital_Circuits - Mixed_Circuits.

Digital FAQ :

Dynamic Digital Tutors - 555 simulator

Usage of Schmitt trigger NAND Gates - I have a question about your Long Duration Timer circuit

Printer Sharing Without LAN - I am from Techno India college

Fuzzy Logic Links - please if you have some materials on Fuzzy logic control

Presettable Up-Down counter-timer - I am looking for a schematic for pre settable Up/Down counter

Seven Segment LED display - how is the circuit for driving a seven segment led

Timers and Counters :

Digital Timers, Counters and Clocks

Timers and Counters along with Analog Process Controllers formed the front end of Industrial Automation. Even today automation systems and control panels use analog timers and electromechanical counters. These are Indispensable. Analog + Digital combination controllers came next which were little bigger and offered better stability. They had thumbwheel switches as user interface in place of potentiometers.

uP based Systems with chips like 8085 came after that, they consumed more power and were big in size. The coming of Cmos uC like 80C31 made Process Instrumentation Small and SMD made even 48 X 48 DIN sizes possible. Now Analog and uC based designs are used in different applications. Digital Hybrids and uP instruments are not used as they were Transient-Technology Methods.

Utility of Testing and Troubleshooting Tools

Many times we cannot carry big or expensive test instruments to the field, so we have to have a troubleshooting tool kit. Continuity testers, Logic Probes, DMM, Clamp Meters etc..

It also is sometimes required to build a quick jig or fixture with electronics to troubleshoot, simulate a problem or to test the reliability or aging of components and systems. Here you need to be cost effective, fast and innovative; and build a simple system with available, affordable or procurable resources. Hence a bit of circuit design, firmware and software are essential skills for production engineering.

You can troubleshoot and repair Electronic Equipment easily with Meters and Continuity Testers. In India the early analog moving coil meters like AVO meters came from Motwane. Then we got Philips Analog Meters, Digital Meters and even Scopes.

Hameg Type Oscilloscopes came early, made by Scientific Mes-Technik. Power Supplies, Function Generators and Oscilloscopes were available from Aplab.

Anantha Narayan

Test Tools Resources

Tuesday, June 09, 2009

Electrical Control Panel Wiring

Just like rackmounts hold big instruments or computers, control panels small or big have to hold DIN Instruments, switches and annunciators to make it easy for the operator. The maintenance work also is simple from the backside. It can be kept near the machinery which it controls.

Some Control panels go into Control Rooms at a distance away or at a greater height from the shop floor. This way they can monitor and give instructions while managing a larger process like processing of chemicals and at the same time safeguarding the instrumentation and computers with controlled environments.

Some of the pdf circuits are not easy to read, some have errors, this is mainly due to the importing of schematics from an older ORCAD Dos Version. I have corrected some circuits, some are to be checked. Also some circuits were not corrected after they were drawn by New Learners, as i wanted them to document what they learnt and familiarize with computers, Some did a good job. This section has no electronic parts, so you can figure out the diagrams.

Some example circuits of panels here Electrical Control Panel Wiring

Anantha Narayan

Related Reading -

Monday, June 08, 2009

Parts or Components in Electronics

When i saw CadSoft EAGLE Layout Editor i wanted to try drawing circuits with it, Some circuits documented from my design note book are here with the editable schematics.

Here are circuits made of Resistors, Capacitors and Inductors which are passive components. Crystals, Thermistors, Varistors, Variable Passive RLC are also Passive Parts.

Zeners, Diodes, NPN-PNP Transistors, FET, MOSFET, SCR, Triacs are all discrete active devices. ICs and Hybrid Modules are made of many discrete and passive components. In the Integrated Circuits or ASICs, all parts even passives are derived on the Silicon Wafer. In Hybrid Modules the construction uses SMD or Tiny Chip components interconnected in a small ceramic PCB and Hermetically Sealed if needed.

Parts like Switches, Connectors, Relays and PCBs are ElectroMechanical parts. Nuts, Bolts, Screws, Cabinets and enclosures are Mechanical parts.

For a Systems Integrator or Control Panel Designer, the Timers, Controllers, PLC which are Electronic Products become Components or Modules along with Contacters, Current Transformers, AC-DC Drives etc.

Related reading -

Mains Voltage and Power Circuits

Mains Power means the 230 V AC 50 Hz or 110 V AC 60 Hz in some countries, The lower power line like 5A is used for small lamps and fans. The higher power line 15A is used to drive the High Power Electrical Appliances like Heaters and Motors. This is a single phase supply.

Single phase Supply in layman language means a Live, a Neutral and an optional earth. The earthing is a must in every building along with lightning protection. The Neutral is a close to earth potential, The live can give a shock to a man who is in contact with earth at some part of the human body. So great care has to be taken. This live wire or point can be easily checked by a quality standards approved Neon Tester.

Three phase supply - there are three Live wires, used in factorys and apartments to power bigger loads and Motors. A 3 phase AC motor is very efficient and economical and most machines like Drills and Lathes are powered by AC Motors. 3 phase supply becomes essential for industry.

The voltage is transmitted and supplied to houses at a high level in comparison to low level of batteries. This High Voltage is not safe but Inevitable, as transmitting at lower voltage means greater current carrying requirements of wires and connectors. That leads to more copper or aluminum usage, more wastage of power due to I2R.

Earthing has to be good, use a Earth Leakage Trip Device. If earth wire gets snapped outside and some appliance is leaking, the metal clad appliances may give shock. Even if no appliance is leaking, the current thru y-capacitors of EMI Filters in Electronic Gadgets like computers are enough to make your Neon tester glow.

Anantha Narayan

Related reading -