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.
From: Charlie E. on 26 Apr 2010 20:16
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.

Charlie
From: Joerg on 26 Apr 2010 20:21
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.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
From: Charlie E. on 26 Apr 2010 20:29
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.

Charlie
From: mpm on 26 Apr 2010 20:33
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
From: John Larkin on 26 Apr 2010 20:39
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.

>
>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.


>
>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

First  |  Prev  |  Next  |  Last
Pages: 1 2 3 4 5 6 7 8 9 10 11 12 13
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.