Don't know about colors having significance for approvals,
[what a good idea] but...
Isn't green light at the center of the visible spectrum
around 420 nm wavelength, and photosensors are most
sensitive in the IR band, around 750nm?
It's my understanding that the usual way to shift the
sensitivity of an optical device is to place an optical
bandpass filter over the device, only shifting the
sensitivity. Shifting the sensitivity in this manner
actually lowers the sensitivity because the full spectrum
is removed and only light of desired bandwidth is allowed
through. Always reduced.
I also thought most plastics [no matter what their visible
color] are pretty opaque to IR.
- Robert -
On Thu, 1 Jun 2006 12:14:56 -0700
"Ralph McDiarmid" <[email protected]> wrote:
> Isn't the physical gap between transmitter and receptor
> very small and
> don't these devices use a narrow band of infrared?
>
> I suspect package colour has nothing to do with optical
> performance or
> at best it's swamped by operating temperature effects.
>
> ======================================
>
> Ralph McDiarmid, AScT
> Compliance Engineering Group
> Xantrex Technology Inc.
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Powell,
> Doug
> Sent: Thursday, June 01, 2006 11:38 AM
> To: [email protected]
> Subject: RE: Why are some optocouplers white and some
> black?
>
> I have one bit of information to add to the mix.
>
> A co-worker, who is more an old-timer than I, recalls
> that when the
> translucency problem was solved it was during VDE
> approvals at some
> company whose name he does not recall. The story goes
> that, as proof
> that the problem was fixed they started using white
> bodies for the ICs
> instead of black. If true, it sounds a little like an
> advertising
> trick.
>
> If there are any opto-folks on this discussion group I
> would like to
> hear your perspective.
>
>
>
> Doug Powell, Staff Engineer
> Corporate Compliance Dept.
> Advanced Energy Industries Inc.
>
> -----Original Message-----
> From: Powell, Doug [mailto:[email protected]]
> Sent: Wednesday, May 31, 2006 11:03 AM
> To: [email protected]
> Subject: Why are some optocouplers white and some black?
>
>
> This is obviously a trivia question but I think is
> related to product
> safety.
>
> My recollection is that early on, some manufacturers
> designated white
> body optocouplers as the only type that had certain
> attributes, like
> agency approvals.
>
> It would seem that a white body would be more translucent
> and you risk
> falsely triggering the transistor.
>
>
> -Doug
>
> Doug Powell
> Advanced Energy Industries Inc.
> Fort Collins, Colorado USA
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