This is a phase angle control of a Triac which is a evolution from an SCR. The 50 Hz or 60 Hz Sine wave of mains can be turned on at any point after the Zero Crossing.
Design Notes - Power Electronics
The Voltage ramps up in the sine wave which gives a near "Linear" slope which can be used to trigger the ON at a time delay after zero crossing when the voltage is zero. This is like a PWM but works on low frequency only.
This is a DC controlled Solid State Relay which can turn 230V AC equipment on and off. The output is like a NO normally open contacts of a relay and have to be in series with the Load like any other switch.
Read more at my main page - Solid State Relays - SSR I used to make them long ago.
This should not be used for large inductive loads like big motors. The Q1 transistor limits the current thru the LED by providing an alternate path for more current. The DC input can be from 3V to 20V.
This is a a circuit from my Power Supplies Section. There may be some documentation errors in my circuits. If you are used to building and troubleshooting circuits then it is ok.
This circuit is derived from an application note of L296, It is a Power Switching Regulator from ST Micro. U1A is wired as a differential amplifier and U1B a High Gain Comparator. C4 and C5 are parallel for lower ESR. Equivalent series resistanc Fast switching diode used is BYW80.
This circuit is an User Interface part of a Security Alertness Monitor that i designed decades ago.
The circuits are here - Digital Circuits - Part 1 The RAM and RTC part is missing, i will add later. It is without uC or Software. Only CMOS Logic.
Every Hour "+V UR" Goes High for 120 Seconds. The Buzzer Sounds and a Red LED turns on. The Guard has to respond by Pushing the Switch. The Green Light Flashes and the external Flip-Flop logic brings "+V UR" Low, The Buzzer Sound Stops and Red Light Goes off..
If not pressed the Sound Stops after 120 Seconds and even the Red light goes off then. This records a Non-Alert Hour in the RAM for that Day. The Ram Stores 9 Days alertness status.
You could try porting this project into a 89C2051 for learning product and interface design.
This is an incomplete version of the power supply used for the Alertness Monitor with hourly LED Display. This circuit used a Dual Color LED. Green meant Alert and Red meant No Alert or acknowledge press.
Power Electronic Circuits - Basic Power Supply Designs
I can write here only in "Electronic English". Focus on the tech not grimmer. It may be like Pascal with a touch of Acronyms, codes and circuit axioms.
The top part is a 5V regulator with 0.7 Diode boost, means 5.7 V DC. The battery was floating on this point above the zener Z4, that connection comes from outside. A protection fuse maybe needed in case Zener draws more current. The Zeners were test selected to get above 6V along with the diode.