Vactrol: Difference between revisions

[[File:Optoisolator.jpg|thumb|right|100px|Schematic symbol for a phototransistor optocoupler.]]The '''Resistive [[opto-isolator]]vactrol''', also known as '''photoresistiveresistive opto-isolator''' (RO), or '''vactrolphotoresistive opto-isolator''' in its simplest form, theis analogan analogue optoisolator consistsor '''optocoupler''' consisting of a [[LED]] and a [[light-dependent resistor]] (LDR) in the same package:. lightLight output from the LED varies as the current passing through it;, the light strikes the LDR, varying its resistance in turn;, in effect this gives a current-controlled resistor.<ref name="ts">[[Tim Stinchcombe]], Mod Wiggler wiki, June 2012&lrm;</ref><ref name="wp">Wikipedia:[http://en.wikipedia.org/wiki/Vactrol#Resistive_opto-isolators Resistive opto-isolators]</ref>

AnThe earlyname manufactureris ofa thesetrademark devicesintroduced wasby Vactec, Inc,. who usedin the trademark ''Vactrol''1960s, and this has since since largely become genericized to cover all such available devices, whoever might make them. Through acquisitions etc., Vactec became part of Perkin Elmer, and recently it appears the Vactrol trademark has passed to a company called 'Excelitas'.<ref name="ts" /><ref name="wp" /> Like a lot of other products used in SDIY though, this is yet another device that is about to become end of life. As the photoresistors typically use CdS (Cadmium Sulphide) in their construction, Cadmium is classed as a hazardous substance under RoHS and production is due to end in 2015. Production would have ended sooner, but Vactrols where given a limited exemption whilst replacement materials were researched.

There are reports of success using the Fairchild H11FxM family.<!-- for what?--> These devices use a silicon photo-detector (rather than an LDR), which behaves like a [[FET]], and so they don't suffer from the lag in response that LDR-based devices have, i.e. they can be modulated at audio rates.<ref name="ts" />

== Manufacturers ==

* Excelitas, [https://web.archive.org/web/20120707054657/http://www.excelitas.com/Pages/Product/Analog-Optoisolators-and-Optocouplers.aspx Analog Optoisolators and Optocouplers]

* Some [[Doepfer Musikelektronik GmbH|Doepfer]] modules are known to use Macron devices, [https://web.archive.org/web/20130731213605/http://macron.com.hk/specification.htm Macron specification page]

* The Silonex 'NSL' series, [https://web.archive.org/web/20120821204302/http://www.silonex.com/audiohm/index.html Silonex Audiohm Optocouplers]

* Fairchild H11FxM, [https://web.archive.org/web/20110607053714/http://www.fairchildsemi.com/tree/optoelectronics/solid-state-relay-optocouplers/solid-state-relay/ Solid State Relay Optocoupler]

== References ==

==See alsoExternal links ==

* There is also much useful info in the Wikipedia article: [http://en.wikipedia.org/wiki/Vactrol#Resistive_opto-isolators Resistive opto-isolators]

* This Perkin Elmer document contains a good introduction to such devices: [http://denethor.wlu.ca/pc300/optoisolators/analogoptoisolatorintroduction.pdf Analog Optical Isolators: Vactrols]

* A more complete Perkin Elmer 'databook' contains not only the spec sheets of the various types of Vactrols, but also has many useful 'application note'-type circuits of how they might be used: [http://www.datasheetcatalog.org/datasheet/perkinelmer/VT500.pdf Photoconductive Cells and Analog Optoisolators (Vactrols)]

* Current spec sheets are to be found on the Vactrol product page at Excelitas: [https://web.archive.org/web/20120707054657/http://www.excelitas.com/Pages/Product/Analog-Optoisolators-and-Optocouplers.aspx Analog Optoisolators and Optocouplers]

[[Category:ElectronicSemiconductor componentsdevices]]