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From: Joerg on 26 Apr 2010 20:41
Charlie E. wrote:
> On Mon, 26 Apr 2010 17:21:55 -0700, Joerg <invalid(a)invalid.invalid>
> wrote:
>
>> Charlie E. wrote:
>>> On Mon, 26 Apr 2010 17:03:28 -0700, Joerg <invalid(a)invalid.invalid>
>>> wrote:
>>>
>>>> Charlie E. wrote:
>>>>> On Mon, 26 Apr 2010 16:14:53 -0700, John Larkin
>>>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>>>>>
>>>>>> On Mon, 26 Apr 2010 15:07:02 -0700, Charlie E. <edmondson(a)ieee.org>
>>>>>> wrote:
>>>>> A note on background leakage. The LED and PT are both oriented to the
>>>>> front of the case. I have black felt glued to the top and bottom of
>>>>> the case (about 1" wide) to block reflections and reduce ambient. My
>>>>> typical 'CLEAR' reading (no LEDs active) is in the <0.5% range. My lab
>>>>> has a large east facing window, and I have done testing both in the
>>>>> morning, afternoon, and evening without a lot of difference. Direct
>>>>> sunlight is another matter...
>>>>>
>>>> Sunlight and thus outdoor ambient has a lot of IR content which goes
>>>> through just about anything. Indoors there will be very little, AFAIK CF
>>>> lamps emit very little in IR percentage and windows keep it out as well.
>>>>
>>>> You might need some foil in there as well, between plastic and felt.
>>> Maybe a possibiliity, but the phototransistor is an ambient light
>>> detector, which has built in filters in the IR range to help shape the
>>> response curve. Pam was more concerned with possible UV contamination
>>> from the bright flourescents in the stores.
>>>
>> Well, it just says "photo npn" in your schematic. Which one is it? IR
>> filtered doesn't necessarily mean is has to be a very good filter.
>
>
> It is a TEPT5600, a 5mm through hole part, which I bend to a 90 degree
> angle to face the front. The LED is a Kingsbright WP154A4SUREPBGVGAW
> RGB LED which I also bend to a 90. I have the LED at a 45 degree
> angle to the face plate, and the PT and LED are on opposite sides of
> the board, to reduce direct reflections between them.
>

Figure 7 hints that this photodiode still lets in a ton of the near-IR
spectrum:

http://www.vishay.com/docs/84768/84768.pdf

Might also be good to put a snippet of metal tubing around it as a
shroud because it seems to be a plastic diode. The more you can reduce
the acceptance angle the better.

--
Regards, Joerg

http://www.analogconsultants.com/

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From: Joel Koltner on 26 Apr 2010 20:43
Lots of places do rainbows... there are various samples here:
http://en.wikipedia.org/wiki/Gayborhood

That phallic-looking one in Boystown, Chicago seems quite fitting. :-)

From: Charlie E. on 26 Apr 2010 21:07
On Mon, 26 Apr 2010 17:39:09 -0700, John Larkin
<jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:

>On Mon, 26 Apr 2010 16:43:40 -0700, Charlie E. <edmondson(a)ieee.org>
>wrote:
>
>>On Mon, 26 Apr 2010 16:14:53 -0700, John Larkin
>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>On Mon, 26 Apr 2010 15:07:02 -0700, Charlie E. <edmondson(a)ieee.org>
>>>wrote:
>>>
>>>>Hi All,
>>>>You have given me good advice in the past, and I am now really close
>>>>to shipping this thing, but still running into some of the same old
>>>>problems.
>>>>
>>>>Basically, when I program a unit, it works great here on the bench,
>>>>and around the house, but when I go out into the real world, all heck
>>>>breaks loose!
>>>>
>>>>My present problems seem to revolve around dark colors. Browns shift
>>>>to dark red, or green, blacks suddenly become dark greens, dark denims
>>>>become black, dark green, or even dark blue-green.
>>>>
>>>>Trying to determine the cause is difficult, because the problems never
>>>>happen in the lab when I am in debug, and can get full data on what is
>>>>going on internally. My present guesses all point to shifts in the
>>>>strengths of the LEDs and other electronics, perhaps with temperature,
>>>>or maybe with differences in background lighting leaking into the
>>>>unit.
>>>>
>>>>So, can anyone offer any suggestions? You can find a schematic and a
>>>>photo of the unit at
>>>>http://edmondsonengineering.com/RainbowColorReader.aspx
>>>>
>>>>Thanks in advance!
>>>>
>>>>Charlie
>>>
>>>
>>>Why is VCC connected to both power pins of U2?
>>>
>>>The + input of U2C has no DC path.
>>>
>>>What's going on with U8/U9/U10, especially U10?
>>>
>>>John
>>>
>>
>>Hi John,
>>The upper pin is connected to ground. The VCC is on top of the bypass
>>cap for the chip...
>>
>
>Oh. OK.
>
>>U2C hasn't given me any problems, to this point. ;-)
>
>It's probably banging up against its own ESD diodes in one direction
>or another. C10 makes the power amp ignore the offset. You could
>remove C4.
>
Interesting. It doesn't really do that much, does it... ;-)


>>
>>U8/U9/U10 are all complementary MOSFET pairs, doing the switching of
>>the LED power to the LEDs.
>
>Why the 100r and 0r resistors S-G on the Pfets? That wastes a lot of
>Vled current... especially the 0r one.
>
Ok, that is an error in the schematic. Those are all three 10K
resistors. It was correct on the board... ;-)

>
>>
>>A note on background leakage. The LED and PT are both oriented to the
>>front of the case. I have black felt glued to the top and bottom of
>>the case (about 1" wide) to block reflections and reduce ambient. My
>>typical 'CLEAR' reading (no LEDs active) is in the <0.5% range. My lab
>>has a large east facing window, and I have done testing both in the
>>morning, afternoon, and evening without a lot of difference. Direct
>>sunlight is another matter...
>
>Are you "auto-zeroing" out the background light? Are you checking for
>sensor saturation?
>
>John

I had built in a test for the 'CLEAR' component, where I measured the
ambient, and subtracted it from the measured values, built in testing
it was always so low I didn't feel the need to keep it in. Might need
to test that hypothesis now...

Thanks!!!!

Charlie
From: Charlie E. on 26 Apr 2010 21:11
On Mon, 26 Apr 2010 17:33:32 -0700 (PDT), mpm <mpmillard(a)aol.com>
wrote:

>On Apr 26, 5:07�pm, Charlie E. <edmond...(a)ieee.org> wrote:
>> Hi All,
>> You have given me good advice in the past, and I am now really close
>> to shipping this thing, but still running into some of the same old
>> problems.
>>
>> Basically, when I program a unit, it works great here on the bench,
>> and around the house, but when I go out into the real world, all heck
>> breaks loose!
>>
>> My present problems seem to revolve around dark colors. �Browns shift
>> to dark red, or green, blacks suddenly become dark greens, dark denims
>> become black, dark green, or even dark blue-green. �
>>
>> Trying to determine the cause is difficult, because the problems never
>> happen in the lab when I am in debug, and can get full data on what is
>> going on internally. �My present guesses all point to shifts in the
>> strengths of the LEDs and other electronics, perhaps with temperature,
>> or maybe with differences in background lighting leaking into the
>> unit.
>>
>> So, can anyone offer any suggestions? �You can find a schematic and a
>> photo of the unit athttp://edmondsonengineering.com/RainbowColorReader.aspx
>>
>> Thanks in advance!
>>
>> Charlie
>
>Hey Charlie,
>Can't help with your circuit, but it looks like a pretty cool device.
>It's the sort of thing that someone probably would never think of
>unless they were familiar with blindness.?
>I wonder if it could have application in teaching kids their colors,
>or for use with colorblind individual.
>Maybe an advanced unit to detect world currencies...??
>
>My only thought is that maybe light is bouncing around in weird ways
>on the input.
>Try setting up some lights on your bench and see if you can emulate.
>Use different types of lights (flourescent, tungsten, basically, every
>wavelength you can think of).
>I would also experiment with different daylight times (outdoors, of
>course), as the Sunlight temperture varies considerably dusk to dawn.
>(You probably already know all this, right??!) Disclaimer: Amateur
>photographer here.
>
>I notice you're in the United States.
>I thought I should point out a potential regulatory concern that
>involves offering products for sale before they have either been FCC-
>certified, or before the manufacturer (you!) has filed a Declaration
>of Confirmity.
>Honestly, I'm not sure which one your product would involve. Probably
>a DoC, but I don't know if they consider the LED emissions to require
>certification...?? Maybe someone here will know.
>Your PIC certainly operates fast enough to qualify for testing. I
>recall anything over 9kHz requires testing, though I could be wrong
>about that lower bound.
>8 to 32 MHz definitely qualifies, however.
>
>I think the FCC might interpret your website as advertising of the
>product, particularly in light of your web text suggesting wholesale
>pricing. (I realize the product is not ready for sale, but that's not
>really the point.)
>If the FCC were to draw that conclusion, it could subject you to an
>Official Citation or Notice of Apparent Liability. The former is a
>slap on the wrist involving no out-of-poekct money. The latter can
>lead to possible fines and in-rem forfeiture - (though all of these
>outcomes are highly unlikely).
>
>Either way, a quick review of the Rule may put your mind at ease. The
>Rule is FCC 2.803
>For convenience, here's the link:
>http://www.gpo.gov/fdsys/pkg/CFR-2009-title47-vol1/pdf/CFR-2009-title47-vol1-part2.pdf
>
>Not knowing your situation, my recommendation is to be safe just add
>the following text to your web site (the page that has pricing info):
>
>This device has not been authorized as required
>by the rules of the Federal Communications
>Commission. This device is not,
>and may not be, offered for sale or lease, or
>sold or leased, until authorization is obtained.
>
>The above is the exact language specified by 47CFR2.803(c).
>
>Enjoy!! And best of luck with the project/product.
>-mpm

Hmmmm...
It is definitely not an intentional radiator, and no clock outputs
leave the chip. The two switchers are only going to a cap less than
10 mm from the chip. Would never have thought anything this simple
could need certification. Jeorge? Any thoughts?

Thanks,
Charlie
From: Joerg on 26 Apr 2010 21:31
Charlie E. wrote:
> On Mon, 26 Apr 2010 17:33:32 -0700 (PDT), mpm <mpmillard(a)aol.com>
> wrote:

[FCC regs]


>> Either way, a quick review of the Rule may put your mind at ease. The
>> Rule is FCC 2.803
>> For convenience, here's the link:
>> http://www.gpo.gov/fdsys/pkg/CFR-2009-title47-vol1/pdf/CFR-2009-title47-vol1-part2.pdf
>>
>> Not knowing your situation, my recommendation is to be safe just add
>> the following text to your web site (the page that has pricing info):
>>
>> This device has not been authorized as required
>> by the rules of the Federal Communications
>> Commission. This device is not,
>> and may not be, offered for sale or lease, or
>> sold or leased, until authorization is obtained.
>>
>> The above is the exact language specified by 47CFR2.803(c).
>>
>> Enjoy!! And best of luck with the project/product.
>> -mpm
>
> Hmmmm...
> It is definitely not an intentional radiator, and no clock outputs
> leave the chip. The two switchers are only going to a cap less than
> 10 mm from the chip. Would never have thought anything this simple
> could need certification. Jeorge? Any thoughts?
>

Well, there are paths of self-certification:

http://www.techintl.com/emcinusa.cfm

I run into this a lot. Is a change serious enough to warrant re-cert?
Most clients do it anyhow, send the stuff to an EMC lab. But it's
expensive, basically we rarely get out of there under $5k. If this is
more like a non-profit product and helps the visually-impaired you may
be able to convince a lab to do a "charity run".

But first I'd fix that "CLEAR" ambient subtraction routine that must
have fallen through the cracks ... whoops ... got to have that :-)

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
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Prev: Financial Management Theory & Practice by Eugene F. Brigham, Michael C. Ehrhardt 13th Edition 2011 Solution manual is available for purchase at affordable prices. Contact me at alltestbanks11[at]gmail.com to buy it today. All emails will be answer
Next: Any insight for Automotive Sensor Inputs/ Front-End Protection.