Saturday, October 20, 2018

Design Notes - Schematic and PCB - 04

PCB Thermal Design Care for Analog Circuit Stability - If you have a hot power chip near a DC analog circuit, the values will drift, take time to stabilize, this happens even if you use 1% MFR 100ppm. The impact is more if the heatsink is not used and vents and coolers are absent,

So in a PCB keep distance between heating power circuits and sensitive analog circuits, some times PCB tracks will carry heat to the Analog area, Hence keep sensitive analog circuits as plugin modules.

Design Notes - Schematic and PCB - 04

When you make a PCB try to orient all ICs in one direction, so also all diode and cap polarities, then it is easy to populate the parts, easy to verify and troubleshoot for production and testing.
High Frequency and RF Design of PCB
  • Sharp bends in PCB tracks or wires will radiate away the RF energy, so do not have hairpin bends.
  • RF or near RF multilayer PCB have 2 layers as ground plane and tracks in the layer in between, Faraday cage.
Schematic Design Basics
  • When we draw circuits we have to keep in mind the readability, the circuit should be laid out, according to the signal flow, the input output ports shown in the periphery of circuit.
  • Drawing a neat circuit diagram will ensure a better design, lesser parts means greater reliability, simple solutions.
    How To Draw Schematic Diagrams 

    A well-drawn schematic makes it easy to understand how a circuit works and aids in troubleshooting; a poor schematic only creates confusion.
      Product Design Mockup and Prototypes
      • Make a 3D mockup of the final product, both the box and the PCB with components before PCB done.
      • The product with the PCbs, transformer and other panel components should fit in the box it was intended for, or the cabinet that was designed for the Product. To make sure make a Mock-up Product - 3D and display. Even if you have all documents and drawings in place.
      • Make sure of IC pin numbers, size and packages and indicate in circuit like 40 pin dip before going to PCB. Also check every EDA symbol in your software with the company datasheet to make double sure.
      • Do not mix mechanical and electrical connections, these leads to failures and frequent need of repairs and service.
      • When using a double or multi layer pcb make one layer a ground plane, all decoupling caps ground linked to it.
      • Reinforce copper tracks on PCB with a copper wire when it needs to carry more current, tinning may improve a bit.

      Friday, October 05, 2018

      Production Notes - Prototype Fabrication - 03

      Prototype Fabrication and Pilot Production are the first stages of a design concept taking a real tangible form. The transition from R&D to Manufacturing Engineering happens here.

      alpha-numeric LCD based on the twisted nematic field-effect

      Early prototype of an alpha-numeric LCD based on the twisted nematic field-effect as realized in the laboratories of the Central Research Laboratories of F. Hoffmann-La Roche Ltd. by Martin Schadt and Wolfgang Helfrich, photo by courtesy of M. Schadt.

      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.

      delabs Notes from 90s

      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

      Search This Blog