Solid State Relay
Solid State Relay Solid State Relays are semiconductor equivalents of the electromechanical relay and can be used to control electrical loads without the use of moving parts Solid State Relay Example Lets assume we want a micro-controller with a digital output port signal of only +5 volts to control a 120V AC, 600 watt load (heating element or lamp). For this we could use the MOC3020 or MOC 3041 opto-triac isolator, but the internal triac can only pass a maximum current (Itsm) of 1 Amps peak at the peak of a 120V AC supply so an additional switching triac must also be used. First lets consider the input characteristics of the MOC 3020 opto-isolator (other opto-triac are available). The opto-isolaters datasheet tells us that the forward voltage, (Vf) drop of the input light emitting diode is 1.2 Volts and the maximum forward current,(If) is 50mA. The LED needs about 10mA to light reasonably bright up to its maximum value of 50mA. However the digital output port of the Micro...