Your Favorite Brand Opto Isolator modules?

What Opto Isolator brands do you like to use, and where do you get them?

What are your favorite modules?

Any undesirable failures or "premature End Of Life" stories appreciated.

What are you trying to isolate? Digital I/Os, communication
signals or something else...?

Opto Isolation for Contactor switch state.

I'm looking for opto isolator to handle mostly voltage sensing applications, such as 480 VAC present.

Current problem: I have a piece of equipment up-stream. I want to know if it is powered up. It runs on 480 VAC. I have only dc inputs available.

Another problemo:
I have 120 VAC Prox Switches, and I only have 10-30 VDC inputs. Any suggestions?

Yet another: I want to know if 208 VAC is present to the hot side of my disconnect switch.

Stuff like this.... which I haven't thought through very well at this point ... and the answer maybe obvious, but I haven't devined it yet.

Opto Isolation resources:
http://www.wolf.agilent.com/litweb/pdf/5962-6894E.pdf

Thanks

Why you dont use Relay.?
Look at www.phoenixcontact.com

Yeah, I would say just use a relay also. BUT, I question why you even care if upstream equipment is 'powered up'? I would be more concerned that it's discharging product, no? That should be handled by a sensor on the infeed of the downstream equipment.

"I have 120 VAC Prox Switches, and I only have 10-30 VDC inputs. Any suggestions?

Yes, buy DC prox. switches, period. IMO, AC prox. switches should only be used as a quick and easy replacement for existing mechanical switches. DON'T use 120VAC for your control circuit if you're building new stuff...

Where you NEED opto-isolation, I like the Opto22 style stuff.

beerchug

-Eric

Opti-Isolators

I have chosen to use an Agistat voltage relay to monitor ac 240 volt service voltage. It provides an excellent isolation.

Not exactly my favorite, Pheonix.

They have a True Opto-Isolator.

They are ridiculously expensive in this regard.

Something like $54 per point.

I remember buying and using Opto-Isolator chips for less than $1.00.

(112)

I have also used opto22 with much success and minimal failures. Having been a plant electrican years ago in a food cannery (wired in 240 volt closed/grounded delta with 240 vac control voltage) that was one big daisy chain, i wish we would have had "isolation". Nothing like working on stuff with all power off, and catching a 240vac signal line from somewhere else that was dead when checked. Electricians usually stayed around one canning season. Did have lights on the hot side of disconnect switches so that you could see them at a great distance, to determine if there was power to the previous production line(s) or if things were down there because of a bad fuse, or ???

It may require a lot of enclosures and isolators and wire, but what the heck, if you can make it easier to troubleshoot, why not.

Big city engineer approach, put in lots of plc's and network them, have staus readouts all over.

Call up A-B and get out the checkbook, sorry, couldn't resist that one.

regards....casey

Please elaborate on DC prox virtues.

Eric Nelson said:

Yes, buy DC prox. switches, period. IMO, AC prox. switches should only be used as a quick and easy replacement for existing mechanical switches. DON'T use 120VAC for your control circuit if you're building new stuff...

Click to expand...

Eric:

Please elaborate on why DC prox's only. Safety? Cost?

Thanks.

Re: Please elaborate on DC prox virtues.

Hester said:

Please elaborate on why DC prox's only. Safety? Cost?

Click to expand...

Safety mainly. I don't think I can explain 'why' any better than Jim Rowell did in THIS ARTICLE over at MrPLC.com.

Read number 8 and 9 in his 'List of Do's and Don'ts'...

beerchug

-Eric

Eric,
Thanks for the link to Jim Rowell's Electrical Safety article. It has some useful information. I agree with all he said. I use the lowest control voltage that I can, but in some cases where I have long runs of wire (200 feet or more), 24 vdc does not work very well. I still use 120 vac for those, knowing that it is more dangerous for the workers. I do install a ground wire in every conduit and do not depend on the conduits for a ground path, even though this has long been allowed by the N.E.C.

What Lancie1 said and more:

Some equipment out there has tag lines or (festoon cable) to suppy power to moving equipment. That being said in many cases you will have 480 vac lying on top of control cables. Electrical "noise" along with length becomes a problem with the physical constraints of a system in special cases such as this. 24 volts in this case does not work well!

As was stated, good grounding is essential along with clearly marked wiring and documentation.

Regards,
Chris