Electronic Engineering Schematics
Interactive Tutorials on Digital Electronics
More Digital Demos
These were tutors which i made around 1999, these are
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 These technologies have been
replaced by the uC systems.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
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
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
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
- 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
- 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.
30th Aug 2020