PCB making(etching) Homemade DIY-very low cost materials

Alternating current(AC) vs Direct current(DC)

Alternating current(AC) vs Direct current(DC)

AC	DC
AC switches direction periodically forward-backward	DC flow in single direction
AC has generally freq.50Hz or 60Hz	DC has zero freq.
AC cannot be stored	DC can be stored in battery
In AC longer transmission is possible without energy loss	In DC longer transmission is not possible due to energy loss
Obtained from ac generator or mains	Obtained from battery, rectifier, DC generator
Types of AC:- Sinusoidal, Trapezoidal, Triangular, Square.	Types of DC:- Pure and pulsating

OPEN LOOP SYSTEM vs CLOSE LOOP SYSTEM

OPEN LOOP SYSTEM vs CLOSE LOOP SYSTEM

Open loop system	Close loop system
The open loop systems are simple & economical	The closed loop systems are complex and costlier
They consume less power	They consume more power
Easier to build	Difficult to build
If calibration is good, they perform accurately	They are accurate because of feedback
OL systems are generally more stable	CL systems are less stable
Optimization is not possible	Optimization is possible
These are not reliable	These are reliable
Easy to regulate	Ability to correct error
There is no feedback	Feedback is always present

Basic difference between Relay and Transistor

Relay	Transistor
It is an electromechanical device	It is a semiconductor device
Works on both AC & DC	Works with DC only
Works on extreme temperature	Working is limited to max. 95 °C and below due to semiconductor
Operates on low freq. 200hertz	Operates on high freq.in (megahertz)
Highly isolated from control coil	Not isolated from base and gate
Only on and off	Can amplify analog signals
Size is more than transistor	Size is very less than a relay

Basic difference between PLC and Relay Logic Control

PLC	Relay Logic
Easy to implement and expand	complex to expand
Troubleshooting and maintenance is easy	Troubleshooting and maintenance is difficult
Can be reprogrammed easily	Reconfiguration is difficult
Interfacing is possible with computer	No interfacing
Required space is less	More space required due to more no of relays
No limitation to no of i/o	Limitation to no of i/o due to complexity
Special training is required	No special training is required
PLC having additional features like PIDs,Timer,etc	No additional features
Wiring is less	Wiring is more
Maintenance required is very less	More maintenance required