|The solid state relay (SSR) is an electronic switch and doesnt have any mechanical or moving parts. This is controlled signal by an opto-coupled SSR which usually uses Light Emitting Diode LED which activates a photo-sensitive diode. The LED turns on the thyristor a silicon controlled rectifier, or MOSFET transistor to switch the load.
SSR are photo-coupled SSR or a transformer-coupled SSR sometimes they use both technology SSR. A photo-coupled SSR is controlled by a low voltage signal which is isolated optically from the load. The control signal in an opto-coupled SSR typically energizes an LED which activates a photo-sensitive diode. This is totaly separated circuit and you dont have to worry of electrocution.
SSRs are faster than electromechanical relays; their switching time is dependent on the time needed to power the LED on and off, on the order of microseconds to milliseconds. SSR lower (if any) minimum output current (latching current) required Increased lifetime due to the fact that there are no moving parts, and thus no wear. No noise also if your are using SSR during switching it is a totally silent operation. SSR is just expensive compared to mechanical operating relay. SSR is $35-40 and ordinary relay is $4-10.
Posted 2010-09-10 and updated on Sep 30, 2010 10:27pm by noel