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More Digital Demos


Digital Tutorials
These were tutors which i made around 1999, these are interactive and started with basic JavaScript and CSS. You can operate the controls and see the Truth Table and Results in LED Displays. Controls include DIP Switches and Push Buttons.

Here is a good book to start learning - CMOS Mixed-Signal Circuit Design - R Jacob Baker

See a Tutor on Digital Numbers - Binary and Hex Numbers see a Basic Digital Product here, made of Cmos chips - Simple Digital Event Counter. These technologies have been replaced by the uC systems.

Both CMOS or uC counting systems are susceptible to spikes, EMI and power jerks. A Solenoid valve operating nearby can reset a CMOS counter or Hang up a uC based Counter. The uC based system needs a watchdog and good EMI safegaurds. The CMOS systems just needs a good supply and isolated input/outputs.

See here a 555 watchdog for uC and uP systems.

Interactive Tutorials on
                                      Digital Electronics

Digital circuits have to have a nice 0.1uF cap at the head of each IC. Decoupling. I/O isolation, no ground loops. Excellent EMI RFI immunity. Power Supply with Capacitor Bank or battery to combat Blackouts and Brownouts. See my answers to a problem here-  RS Latch Erroneously setting by Itself.





The CD40xx CMOS family can work at even 3V-9V-12V DC and consume low power. The speed is not as fast as 74xx TTL family. It is good for simple portable battery powered circuits. The 74HCTxx series is good for low power and high speed but will work at 5V. When you have problems interfacing CMOS and TTL use 74HCTxx family.

Amps-n-Volts Notes Corrected Improved

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. It has listed my jots and notes in pages, designs and the brain accumulated for more than two decades.

 Amps-n-Volts Notes Corrected
                                      Improved

Learning the way Electronic Things Behave

  • 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.

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