delabs Circuits

Showing posts with label Production-Notes. Show all posts
Showing posts with label Production-Notes. Show all posts

Saturday, July 02, 2016

Prototyping to prove a Design Concept

Before simulation in EDA tools. First stage of concept proof or design tweaks were made on BreadBoard, Stripboard or General Purpose PCB.

Even now it is used after simulation or directly. Many RF and Power electronics designs may have to be verified and modified on Pilot Production. Digital Designs and Software/Firmware checks don't need hardware prototypes, but need a proven framework to test it on.

Prototyping to prove a Design Concept

Hobby and Education learning must use breadboards alongside simulation, even though educational eda tools are used. Breadboard connects us with the reality, the way it is. Then you will even simulate better. Robotics and Developing Mechatronics Solutions may need prototyping and modifications many times over.

Soldering and Shiny joints are everything in electronics. One dry solder, a cut track, a solder bridge or splatter near the IC can make a card malfunction.

Thin copper tracks taking high currents, HV and LV circuit isolation, Ground loops, RF Antenna Effect, Ground Plane and Guard rings are just some things to know on Component to Component Connections, that make a huge difference.

In Design Notes of Soldermans Basic Electronics you will find my learning notes in electronics. How this learning happened ?

I had setup my Hobby Science/Electronics Lab when i was in School, In college i was helping others learn practical electronics. I worked in Product Design and Engineering Departments when i was Employed. During this time my Electronics Lab was a Free Training Center, sponsored by my own pay. Then i started my manufacturing firm.

More reading  - Luciani.org Breadboard Hints - John Luciani explains how to prototype a circuit to try out a concept

delabs

Saturday, January 17, 2009

Production Notes - Prototype Fabrication - 03

Prototype Fabrication

Sometimes a component can be defective, may not be what it is labeled or may be of a wrong value. In manufacturing 100% incoming inspection of components can catch these errors, Before Assembly of prototypes just test all passive and active components with a DMM and put all ICs in bases, then troubleshooting is easy.

  • When you make your prototype check diode and el-cap polarity, check pin 1 of chips and connectors, resistor values, dry solder and loose contacts, hairline cuts or shorts, e-b-c etc. of Transistors, FETs and thyristors.
  • Observe color code in wires. positive is red and negative is black and green is earth and See Wire Color Code.
  • When you are soldering or cutting leads, room should have cross ventilation, protective glasses for eyes and a good stand.
  • When using a sharp blade the cutting stroke must move away from you and make sure nobody is close, Wear protective or even plain glasses, If you use a blade with the stroke moving towards your body it will cut badly.
  • Power tools and machinery must be used only after exhaustive training and with safety precautions. The power tools used carelessly and wrongly can cause an injury which will last a lifetime or may even handicap you.
  • Have a lathe lamp or table lamp with a 40W edison-filament lamp (ordinary bulb) on your workbench.
  • Have an antistatic mat on the work or test table, if you cannot afford or get it then get a large aluminum sheet, laminate it with an insulating polycarbonate sheet and earth the metal plate with two 1M resistors in series.
  • Use thin multi strand teflon wires for your jumpers within a PCB, these are not damaged by your iron too.
  • Silicone shrink sleeves can withstand high temperature and use this in your work to make it safer and neat.
  • When you make a connection with a wire you need mechanical strain relief or on use connection will open.

Soldering and Desoldering Tips

Use the soldering iron as a heat transfer tool, heat the junction of the lead of the component and the copper pad on pcb then touch the hot junction with a flux cored soldering lead wire, it should melt and form a concave shining joint. If air bubbles are formed or you see dull convex joints, then it means you have a dry solder and bad contact. Leads of old components due to exposure to moisture, brine or sunshine will corrode, store them well cool-dry-clean-air. Anyway scratch them with a blade and solder them with extra flux.

When you are desoldering a double sided pcb, use a desoldering pump or desoldering wick. Heat a joint to be desoldered and then quickly tap it hard on the table, the molten lead will fall off.

Friday, January 16, 2009

Production Notes - Electrical - 02

All Electronic Products have interfaces to external electrical circuits. The power supply is also derived using converters or power supplies. Motors, Heaters and Transformers are examples of components in the electric power circuits.

  • 12V lead acid batteries should be charged with a constant current CC and constant voltage charger the CV being 13.6V. Deep discharge and over charging will reduce the cycles.
  • Lead acid batteries need a monthly distilled water update to ensure long life, sealed lead acid dont need attention. Keep lead acid batteries in well ventilated area due to acid fumes.
  • Electric Shock can kill hence take great care, Electrolytic capacitors burst and Transformers catch fire. turn off equipment after use. turn off all electricity when going out of town.
  • Inductive kickback starts a tubelight or automobile as high voltages are produced when current in inductor is turned off. This also is the cause of failure in power semiconductors.
  • Earthing is important, ensure it's perfect, the neutral to earth could be 5V AC max., also a circuit breaker and fuse a must. Use a electrical earth leakage circuit breaker to protect both man and machine.
  • Extra care should be taken to prevent injury to eyes while working. Also 230V/110V shock can be fatal. working on high energy electrical circuits and power electronics should be with all precautions.
  • You need a Fuse, Circuit breaker and earth leakage circuit breaker for safety against shock and fire hazard.
  • High voltage or current stress, mechanical vibration, user misuse, High Energy stress (freq and voltage), aging (cycles) cause failure.
  • Good earthing, servo motor regulated mains supply, earth leakage circuit breaker and over current circuit breaker, HRC fuse are some safety steps to take.
  • When working with HV or HE circuits wear shoes, keep yourself dry, the supply board should have above protections in red.
  • Use silicone shrink sleeves to insulate or close exposed high voltage wire ends or joints.
  • Sparking at the high voltage mains supply power contacts like a plug can cause electronic gadgets to fail.

Production Notes - Electromechanical - 01

Production, especially prototype testing and Pilot Production exposes lot of engineering and serviceability issues. When you mass produce, it is more streamlined, yet the scope for improvement never ends. The process should always be open to feedback and improvements.

  • The tracks or components on a PCB should not be near the mounting holes, the tracks may form electrical connections with the cabinet earth if they touch the pillar, washer or nut-bolt.
  • When you tighten the screws-nuts-bolt, limit torque by feeling or with torque limit screwdrivers, or thread will slip or PCB-Cabinet break, or CRT-Glass-Plastic will crack-shatter.
  • After assembly and testing is over on a board, do not drill-file it, it should have been done before. Else components crack or tracks break or small metal pieces will form shorts.
  • The Mechanical and electro-mechanical must be streamlined before production, for example when fitting the board the screwdriver may slip and break a zener. The product should be engineered in such a way that it fits easily and the testing and quality checks need not be repeated.
  • Some mechanical failures may not be visible but may show up as a field failure after even 3 months. this will make you lose further orders and ruin the reputation. Hence engineering is vital.
  • Alumina-Aluminum oxide powder mixed in epoxy resin (araldite) can make thermally conductive insulating filler, heatsinks. The Alumina must be free of moisture and very dry.
  • When you drive nails into walls ensure that that part of the wall is free of mains, telephone or any wiring.
  • Some pcbs can have hairline cuts or hairline shorts which will make troubleshooting difficult.
  • Never put or remove ICs, cards or plug-in modules when the power to that system is on, power off system wait for some time for caps to discharge, then insert ICs or cards, applies to PCs too, USB and Firewire ports are exceptions as they are hotplug, anyway even in this, take a bit of care.
  • Use RTV (room temperature vulcanizing) silicone rubber compound or Varnish on PCB-devices to avoid corrosion-dust. more so in industrial environment, ships and chemical industries.
  • Whenever you use nuts and bolts to fasten a PCB or parts to a cabinet use a spring washer, double nut or adhesive to prevent slip. When a loose nut falls on the pcb or transformer sparks will fly.
  • Do not mix mechanical and electrical connections, these leads to failures and frequent need of repairs and service.

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