delabs Circuits

Showing posts with label Design-Notes-1. Show all posts
Showing posts with label Design-Notes-1. Show all posts

Thursday, June 05, 2014

Amps-n-Volts Notes Corrected Improved

I have corrected, enhanced. moderated my design notes from my earlier Amps-n-Volts News Letter. My knowledge is limited to my experience, observation, perception, learning and beliefs, but i have to express my views freely. These posts are mirrored at Soldermans Basics.

Amps-n-Volts eMag

Near 2001 i started sharing my learning and experience in Electronics Engineering on Blogs and Newsletters. One of the Successful eMag and electronic email magazine ran for five years. I lost interest later in the email mag, and this magazine just morphed into a dozen or more Tech Blogs that run today. From the feedback i got, it has helped engineers and enthusiasts worldwide in Electronic Product Design.

Amps-n-Volts Notes Corrected Improved
  • Before you open a PC remove power, telephone modem and LAN cables else finger and screwdriver in wrong place can zap chips.
  • The products that survive the infant mortality time of say first six months will last quite long.
  • NTSC is like 320 x 240 pixels, which is TV, which is lower than your computer's 800 x 600.
  • When a microwave oven is turned on, a big spike is caused in the power line due to heavy inrush current on start up, Even pumps and motors cause such short time surges. This causes tripping of electrical protection circuits.
  • When a tree branch falls on the high voltage overhead electrical lines, they spark violently and supply trips.
  • Big or tall trucks go in small roads they may snap all low level cable or telephone wires on their way.
  • Do you need to turn on many equipments-machines all at once? do it one after an other sequentially or use a timer for delays. This is because at peak power demand time, turning on all can cause your fuse to blow or worse.
  • A battery that can be charged is best charged in CC constant current and CV constant voltage modes, that means both current and voltage have to be limited. When a battery is deep discharged many times it will age fast, and an empty battery will take huge currents so limit current. overcharging a battery will killit. After a voltage level is reached it should only trickle charge in mA and a battery has to be cut off on overload or before deep discharge
  • The Lead acid battery breathes a lot, so keep them in a well ventilated open space but rain proof. Use sealed maintenance free battery when possible, these are safer.
  • Teflon tape can be used to make leak proof pneumatic or hydraulic connections if junctions are leaking.
  • The current thru a 3mm or 5mm LED (light emitting diode) should not exceed 20mA, 15mA is quite good.
  • In a circuit swap all PNP and NPN , reverse all diodes and el-caps, reverse the supplies and input polarities, most of the circuit may still work like they did before.
  • A sharp bend in a PCB track is a huge inductance (say 1nH ) when it comes to RF. it may radiate or reflect, it may even act like an antenna and pick up RF from the SMPS, Motor or Cellphones nearby.
  • Persistence of vison around 16 frames a second (60mS) hence very fast events not seen .
Some of these points may be repeated and some not relevant in the present technical engineering scenario. As issues may have been set right, years back.

Amps-n-Volts Archive

Instrumentation Notes

Design Notes

Production Notes

Wednesday, January 21, 2009

Design Notes - Product Development - 07

Product Design includes Schematic and Firmware Design. The Mechanical Engineering that goes into making the enclosure and internal construction is also important. The Electromechanical design which is made of electrical circuit, pcb, panel-parts and cable management is sometimes so involved that it is developed with the help of vendors or suppliers.

Product design engineering also needs to take care of the costing and related issues. The costing includes the one time investment on design and tools, even custom Mold-Die, Jigs-Fixtures etc. The engineering costs are amortized over the quantity produced, in a product type life-cycle. Manufacturing small quantities is expensive, large quantities depends on marketing and customer base. Hence custom product manufacturing is a specialized technology all-together, this needs to be modular, programmable and configurable.

  • Just like in ICs, product design is of three types commercial, industrial and military or medical.
  • Quality: cost effective design, quality components, quality workmanship with good testing can result in a quality product. The packaging and production engineering too is important.
  • Whatever be the specs, design or simulation nothing like a prototype being tested by the customer in his environment. So do not go into volume production till such a test is done.
  • Design as per inventory : when you design a new product, we can design it with new types of parts, but it is also important to use parts that are standard to the company's inventory, Also you need to use up the parts which have been accumulated due to a discontinued product line or a failed idea. This way the design becomes more frugal and efficient. It also saves the company to build a new part type stock.
  • A Temperature Controller was fixed in a PCB manufacturer's Works, The readings was fluctuating and soon stopped working properly, the service engineer went and found that there was a strong smell of ammonia around the unit. When opened the tracks were eaten away by rapid corrosion and some of the component leads had disappeared. So another controller was made with extra coats of lacquer-varnish all over and RTV compound in many places. That solved the problem. For large numbers vacuum impregnate modules in epoxy resin.
  • Reworks or fixes will add rapidly to the BOM bill of Materials Cost. Then cost of servicing. So customers are of five types home-user, industrial, hazardous, military and medical. So Components are to be selected and product engineered and costed accordingly in that order.
  • If a product gives three years life with minimum service support it can save itself from building a bad reputation. six years will establish the brand on a long term basis, twelve years of product life you will have the user of the product selling for you. if you want to improve sales by giving a new model every three years, you will need a lot of innovation on the product and you need to buy back the old ones for a big discount, you can bear some cost for brand loyalty and hence build a reputation for more sales in the future. This implies proper and sensible investments in product design and development, engineering, reliability, standards and quality will help a company survive long term.
  • Theory and simulation can give you only part of the picture, you have to breadboard to test properly.
  • In schematic indicate pin numbers of every IC or map the correct part if manual place and route is used.
  • Keep functional blocks of circuits as modules or separate areas in a big PCB, this helps in testing and troubleshooting.
  • When you design an equipment keep the controls minimum, too many options and too many knobs and dials are not good ergonomics . For your equipment to be user friendly use simple navigation and not menus nested 6 deep.
  • Power circuits, digital circuits and analog circuits should have separate supplies and ground when possible.

Sunday, January 18, 2009

Design Notes - Components Selection - 05

Selecting the parts for your product design, choosing the components intelligently is a part of Product Design Engineering.

Budget, Availability, Size, Alternate Vendors, Product Life and Quantity to be manufactured are some factors that determine the selection of a prudent and experienced design professional.

To choose the right type of part, an exhuastive knowledge of the behaviour of passives and discretes is essential. Some points i remember among the things that i learnt the hard way are listed below.
  • Over rate components at least double, if you need a 1A-100V-100uS diode, use a 2A-200V-50uS diode.
  • Electrolytic capacitors have a shelf life, if you need to store them you have to charge them every month.
  • Gold plating is used in connectors because it has low contact resistance and does not corrode or react
  • Use a 100uF and 0.1uF CD in parallel to filter because the inductance of 100uF is a lot (the electrodes are wound as in a coil) and high frequency passes over and is filtered by the 0.1uF which has negligible inductance.
  • Ceramic capacitors leak a bit, electrolytics leak a lot but plastic or mica capacitors do not leak at all, near perfect. An oscillator with a RC time setting needs a plastic cap for stability.
  • In industrial electronics equipment, connectors are a source of many problems, hence avoid connectors. vibrations, corrosion and frequent usage will result in strange problems.
  • Small signal diode 1N4148 switches at 4nS, current of 70mA and 70V withstand capacity.
  • 2N2222 and 2N2907 form a fast switching NPN-PNP pair and have been around for decades.
  • LED displays are best indoors and are not so good for sunlit outdoors, LCD is good for that.
  • All electromechanical parts like switches, relays, connectors and pots have limited number of operations.
  • Failure of parts are when parts are stressed beyond limit, bad environment, misuse, infant mortality and normal aging.
  • Most pots have a dielectric insulation between metal pot shaft and terminals of 1KV or more. Some commercial pots may have lesser breakdown voltage and that will be a product safety issue. So either way use Plastic Knobs or pots with plastic shafts.

Contents

Basic Electronics
Basics of Electronics
Product Production
Work Discipline
Testing Points
Learning Electronics
Electronics Theory

Production Notes
Prototype Fabrication
Electrical Circuits
Electromechanical


Library
Scots Guide Electronics
Engineering - Wikibooks
Design Lab - Jim Svoboda
DC Circuits UOG
Socratic Electronics
Blobz Guide Electric Circuits


Product Design
Product Development
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
Teaching Instruments
Charles Proteus Steinmetz
Muntzing a Circuit Design
Teralab Electronics projects
Historical Instruments


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