[archiver]

Posted by Thomas A. Frank at 03/27/2001 1:39 PM EST


Engineer on team #121, The Islanders/Rhode Warrior, from Middletown (RI) High School and Naval Undersea Warfare Center.


In Reply to: No Engineer, but...
Posted by Kevin Sevcik on 03/27/2001 11:59 AM EST:



Hi;

Opto-couplers and opto-isolators are not necesarily the same thing, and SSR's can be different still.

Today, where I work, the usual useage of the term optoisolator is a four terminal device where the "input" side is an optical source (an LED), and the "output" side is a transistor whose "base" control is the light generated by the input light source. These are a digital device, on or off...so the base is either putting the output transistor into cutoff or saturation.

An opto-coupler, on the other hand, could be the same as above, or it might be an analog device with a similar method of operation, and properties...in other words, the output side might be gain controlled by the amount of input signal. Such devices are great for having low power electronics like a computer control the power output of high power amplifiers.

Note that I say "today", because in times past, such devies were made using a light bulb on the input side and a cadmium sulfide photocell (variable resistor) on the output side. But I haven't seen those commercially in quite a few years. You could make your own, however. Just not for FIRST use (yet!).

SSR's may or may not be optically based, depending on how they are implemented. I've seen ones that were optically isolated, and ones that were not.

Get yourself catalogs from Newark Electronics, Allied Electronics, and Digi-Key, and look at the selection. Then go to the manufacturers web sites for more deatils.

Tom Frank