opto isolator replacement

[david_uk]

Hi - I use a number of opto isolators in my circuits, and I make them up by hot-glueing an LDR to and LED and sealing them in heatshrink. I'm wondering if there's an off-the-shelf way of replacing this arrangement that might be more consistent in how it works? Also I've heard that LDRs are being outlawed by the EU, and sometime or other that may be strictly enforced... In which case I'd be totally screwed!
The resulting resistance goes from a mega-ohm or more down to a few hundred ohms. I use them more for converting a current into resistance (inversely), than for their circuit isolation properties.
Thanks!

[midwayfair]

There are plenty of different optoisolators in chip and vactrol format that are in compliance with the EU's rules. If you post a schematic showing what they're actually doing in your schematic, someone here might be able to give you an alternative.

[R O Tiree]

We'll all be screwed if ROHS is enforced on these devices. Silonex are still making their range of LED/LDR opto-isolators, I think - it might be worth giving them a ring on 01606-41999 to find out what the future holds (their UK distribution HQ is in Northwich, Cheshire).

[armdnrdy]

 Excelitas Technologies Corp. still lists the VTL series of Vactrols on their website. I don't see anything about ROHS compliance though.

[R O Tiree]

I looked on Farnell earlier... Excelitas and Silonex LED/LDR optos are not ROHS compliant.

[drolo]

Also I've heard that LDRs are being outlawed by the EU, and sometime or other that may be strictly enforced...

Why Oh WHY ??

What could possibly be wrong with LDR's now?

I tell you, I live in Brussels and whenever i walk past the place where all the EU parliament is, i get the shivers ...

[samhay]

Also I've heard that LDRs are being outlawed by the EU, and sometime or other that may be strictly enforced...

Why Oh WHY ??

What could possibly be wrong with LDR's now?

I tell you, I live in Brussels and whenever i walk past the place where all the EU parliament is, i get the shivers ...

LDRs that respond to visible light contain cadmium sulphide (that's why they are also called CdS cells) and cadmium is one of the 6 baddies on the RHoS list. LDRs and 'vactrols' that contain Cd are still readily available, so I wouldn't start worrying yet.
As a guess, CdS cells will probably start getting difficult to obtain that same time Pb solder does.

[drolo]

I see ...

I guess there is no alternative to LDR's without cadmium sulphide, is there?

Lately I have been starting to feel like an almost extinct dinosaur ...

[samhay]

I see ...

I guess there is no alternative to LDR's without cadmium sulphide, is there?

Lately I have been starting to feel like an almost extinct dinosaur ...

While I haven't seen them in the wild, there are other types of LDRs that use other weird transition metals rather than cadmium. I think these tend to absorb in the infrared, so we would have to start using IR LEDs, which are not too hard to find. Good luck debugging those.

This is a forum largely dedicated to analogue audio applications, which are often designed to make our gear sound like it did in the good old days. I suspect most of us are, at least in our leisure hours, dinosaurs.

Oh. Optocouplers - LED/FET and LED/transistor packages are RoHS compliant (no CdS cell), but they are a little difficult to use as variable resistors.

[puretube]

Funnily ( ? ) CdS is allowed in solar-panels, afaik...

RoHS

[R.G.]

Some exemptions (all expected to expire on or by 20 September 2015 or 2017 for the medical category)[15]:
...
    Cadmium in Solar panels - Cadmium telluride (CdTe) thin-film PV modules in photovoltaic panels are explicitly allowed by RoHS to contain cadmium, even though cadmium is restricted in all other electronics. The solar panel exemption was in the original 2003 RoHS regulation and it was further extended on May 27, 2011.[17]

Photovoltaic applications are politically correct, and viewed as morally righteous by the Ruling Class. So they are exempted, for a while at least. Photocells (LDRs) are not politically correct, in fact outside the notice of correctness, and so are viewed as "everything else electronic", and not excepted, I believe.

I believe the reasoning is that any possibility to force populations into non-fossil fuel, non-nuclear energy sources must be taken. Solar photovoltaic is to be encouraged in all ways, in spite of a simple engineering analysis showing that solar photovoltaic generation is not yet at "break even" in that more energy is needed to produce the PV arrays than will be harvested with the PV arrays in its projected useful life.

It is odd that the economic repercussions of such regulations do not get noticed. When you do things which are not economically sound - that is, do not return a profit of at least zero, but are instead negative returns - it is the same thing as spending your savings on a personal basis. Eventually the savings account goes to zero, and you can only continue spending your "savings" by borrowing against future productivity. Governments, which can make the laws, will universally allow themselves to do this as long as they can. The problem comes when the ready sources of loans no longer believe they'll get repaid. This is an issue with the EU now, I believe.      

It's not just the repercussions of single, huge decisions that cause problems. It can also be the accumulation of small steps into economic irrationality. It will be sad if the nominal objective of preventing slow poisoning of people by tiny amounts of waste chemicals fails because the long term economic issues and consequences of the mind set that leads there are not addressed. Sad.

[gritz]

@ david_uk: if you are in the UK then Farnell do a pretty wide range of resistive opto couplers - depending on your application the most important property may be the component's response time, but I think that all bases are petty well covered there.

I'll echo what R O Tiree says too - give the Silonex distributors a ring to see if they have any info on the long term situation. Maybe shoot an email to Farnell Customer Support and your local MEP too.

I find it quite amusing (and politically telling) that energy saving light bulbs contain mercury. Saving the planet, one murder at a time!

[drolo]

reminds me of the company that I work with, which has about 600 cargo planes flying around the whole world every day and come up with eco friendly campaigns asking employees to turn off their monitors when they go home ...

... I'm going to live in Autarky as soon as I can find it in Google Maps ...

[Mark Hammer]

Photovoltaic applications are politically correct, and viewed as morally righteous by the Ruling Class. So they are exempted, for a while at least. Photocells (LDRs) are not politically correct, in fact outside the notice of correctness, and so are viewed as "everything else electronic", and not excepted, I believe.

I work alongside policy folks, and find they generally operate on a different plane of existence.  I'd like to say it is as compatible with "our" way of thinking as Lego and Megablocks are with each other...but I'd be lying.  Sixteen years and I'm still trying to figure them out. 

[R.G.]

I work alongside policy folks, and find they generally operate on a different plane of existence.  I'd like to say it is as compatible with "our" way of thinking as Lego and Megablocks are with each other...but I'd be lying.  Sixteen years and I'm still trying to figure them out. 

Romulans doing staff work for Klingons who are too smart to use bat-leths in public is a good first-order fit.