Optoisolator or optocoupler

[Cruznike]

Hi there,
i was wondering if anyone can englighten me as to why do some of the
circuits that i see
some people used the MOC3021 optoisolator for a dimmer circuit and some
use the CNY17-3 optocoupler for a zero crossing circuit?
isn't it true that optoisolators and optocouplers are the same? could
anyone enlighten me a little?

 

[John Popelish]

Hi there,
i was wondering if anyone can englighten me as to why do some of the
circuits that i see
some people used the MOC3021 optoisolator for a dimmer circuit and some
use the CNY17-3 optocoupler for a zero crossing circuit?
isn't it true that optoisolators and optocouplers are the same? could
anyone enlighten me a little?

Optoisolator and optocoupler are used interchangeably.

 

[mpm]

isn't it true that optoisolators and optocouplers are the same? could
anyone enlighten me a little?

I'm not "certain" there's any difference, but here's my take on the
terminology...

Both are used to interface two separate circuits by optical means.
This could be level shifting, solid state relaying, etc..

I always think of OptoIsolators as being self-contained, closed
devices, usually packaged in a dark container or package, where the LED
and phototransistor essentially face each other in the dark.

On the other hand, I think of OptoCouplers as devices that are "open"
to the outside world. Where a slot is present, a or material detection
by reflection capability occurs.

One "couples" information from outside the package, whereas the other
"Isolates" (already present) information across the package. (I
know..., it's a pretty lame description!)

But an interesting question, and one I haven't thought of until now.
Maybe someone will provide the definitive answer (if there is one)
shortly...?

-mpm

 

[John Devereux]

Optoisolator and optocoupler are used interchangeably.

Althought the two example parts are different; IIRC the MOC3021 has a
triac output (for AC loads) and the CNY17 has a transistor output (for
DC).

 

[Cruznike]

John, perhaps you could be right,
even though they are both opto-electronics but it is what it is used
for that actually differentiates it,
since the MOC3021 is used to drive a triac whereas the CNY17 is used to
drive transistor outputs but is unable to drive a triac.
or is it posible? Any thoughts anyone?

 

[John Popelish]

John, perhaps you could be right,
even though they are both opto-electronics but it is what it is used
for that actually differentiates it,
since the MOC3021 is used to drive a triac whereas the CNY17 is used to
drive transistor outputs but is unable to drive a triac.
or is it posible? Any thoughts anyone?

There is great variety available in opto isolators/couplers.

About the only thing common is an IR LED as the input
(though you will find a few that use incandescent lamps).
The output side can be a photo diode, photo transistor,
photo darlington transistor, gate, SCR, TRIAC, photofet,
photo resistor or photo voltaic cell. Some include an
electric field shield between input and output, some do not.
And if you look a bit, you may find something I missed.

Some provide galvanic signal isolation while coupling the
signal with with a light beam, and some couple a signal with
a light beam while providing galvanic isolation.

 

[Henry Kiefer]

| Cruznike wrote:
| > John, perhaps you could be right,
| > even though they are both opto-electronics but it is what it is used
| > for that actually differentiates it,
| > since the MOC3021 is used to drive a triac whereas the CNY17 is used to
| > drive transistor outputs but is unable to drive a triac.
| > or is it posible? Any thoughts anyone?
|
| There is great variety available in opto isolators/couplers.
|
| About the only thing common is an IR LED as the input
| (though you will find a few that use incandescent lamps).
| The output side can be a photo diode, photo transistor,
| photo darlington transistor, gate, SCR, TRIAC, photofet,
| photo resistor or photo voltaic cell. Some include an
| electric field shield between input and output, some do not.
| And if you look a bit, you may find something I missed.
|
| Some provide galvanic signal isolation while coupling the
| signal with with a light beam, and some couple a signal with
| a light beam while providing galvanic isolation.

Yes and there is the strongest isolation type remotely operated:
A optical link as used in audio systems.

And another one:
photointerrupter

- Henry