Maker Pro
Maker Pro

More questions on color reader...

C

Charlie E.

Jan 1, 1970
0
I wasn't too sure about whether the LED's were modulated, and if so,
at what frequency, etc..,

Your device appears to be in the same family tree as small battery-
powered calculators and TV remotes.
In other words, a Class-B (household) digital device, configured as an
unintentional radiator
Note: A digital device is pretty much anything with a clock faster
than 9 kHz.

Typically, these types of devices will have DoC's, and I suspect yours
should as well.
That said, the rules appear vague and flexible enough to allow
Verification.

See FCC Rule 15.101. Link:
http://www.gpo.gov/fdsys/pkg/CFR-2009-title47-vol1/pdf/CFR-2009-title47-vol1-part15.pdf

Sorry to rain on your parade, (if I have?). Just thought you should
be aware, particularly given the advertising thing.
The good news is that Verification / DoC is a lot cheaper, easier and
faster to get than a full-blown TCB Equipment Certification.

Again, best of luck getting the bugs out!
-mpm

Ok, heart attack over. From the FCC at
http://www.fcc.gov/oet/ea/ea_app_info.html

looks like we don't even have to file anything, just put a note in our
instructions that we meet (verification) the specs. Whewwww... you
had me worried there!

Charlie
 
T

tm

Jan 1, 1970
0
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.

= Well, yes, of course that happens. You're looking at ratios
= of RGB light intensities, and when the color is dark, your
= inputs are
= R = 0 + noise
= G = 0 + noise
= B = 0 + noise
= and it isn't surprising that the ratios are dominated by ... noise.


Therefore, he should set a threshold above noise and call anything below
that "dark".
 
J

Jon Kirwan

Jan 1, 1970
0
<snip>
So, can anyone offer any suggestions? You can find a schematic and a
photo of the unit at
http://edmondsonengineering.com/RainbowColorReader.aspx

I did offer a thought, earlier. No response to it.

Have you read and do you fully understand the CIE 1931 and
1964 color standards? (If you are really into this, I'd also
recommend Edwin Land's work papers from the late 1970's to
early 1980's -- you may not need to, but it is just very
interesting to study and it addresses directly some points
that relate squarely on various lighting situations as you
are encountering.)
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.

Which is exactly the area that Edwin Land highlights in his
research reports...

In other words, how much do you understand about human color
perception?

By the way, what are you using as your comparison "standard?"
Your eye? Or?

Jon
 
J

Jon Kirwan

Jan 1, 1970
0
No need to get snotty. The question on the floor is _electronic_, lab
versus _field_.

Which _is_ a question at hand, I suspect.

Jon
 
J

JosephKK

Jan 1, 1970
0
I'm in another country Charlie, but have had similar compliance issues with
low volume items. If you feel the need, find a friendly EMC test lab andsee
if he will rent himself to you for a couple of hours & provide you with a
couple of spectrograms to show that emissions are acceptable. The cost goes
up up up if the lab writes up any report for you.
Doing so would go a long ways in demonstrating due diligence. Test as
many units as you can afford and document them all.
 
J

JosephKK

Jan 1, 1970
0
No need to get snotty. The question on the floor is _electronic_, lab
versus _field_.

...Jim Thompson

While i did not read Jon's post as snotty, i can see how it can be read
that way. It struck me more as a "did you know of this(?), which seems
like it would be helpful".
 
J

Jon Kirwan

Jan 1, 1970
0
While i did not read Jon's post as snotty, i can see how it can be read
that way. It struck me more as a "did you know of this(?), which seems
like it would be helpful".

Thanks. It was offered in that vein.

The funding of accurate human color perception _measurement_
dates back at least to the time when colored house paints
began to be sold (by Sears, for example) as something to
'spruce up' homes. (Turn of 19th to 20th century, roughly.)

Customers would buy a 'brown' for an addition, hoping to get
the same 'brown' they ordered two years before, and getting
something that 'any idiot' could see wasn't even close. The
control of paint chemicals and dyes wasn't sufficient by
itself at the time and there was a strong need for some
"feedback" to help adjust the dyes, as appropriate.

This commercial desire played into a university research
desire regarding color blindness and provided a substantial
funding source for this research to proceed.

A method was needed so that a 'brown' paint bought today and
used on the shady part of a home would look the same as the
same 'brown' paint bought next year and used on a well-lit
side. Side by side, the two paint jobs should "look the
same" to a viewer -- VERY WIDELY varying lighting conditions.

The CIE color system has remarkable fidelity for that
purpose. It also can deal with lighting conditions within
some limits.

What it does not do is cope with the surroundings, which in
human perception is very important. That is one reason why I
pointed him at Edwin Land and one reason why I wondered how
Charlie was determining when the color reading was wrong or
right.

If you take a canvas and place it on a painting easel and put
swatches of colors nearby each other on that canvas and light
it with a bright 100W tungsten bulb, people will see the
colors a certain way. Then, as you dim the bulb down, the
Planck radiation curve emitted will shift dramatically in
wavelength -- all of us here are well aware of this fact --
causing reflections and the resulting distribution of
wavelengths from the surfaces to be markedly different than
before. Yet even operating at 10W or even 1W of output, with
the distribution almost totally different than before, a
human will still "see" the same "colors."

Do the same experiment, now instead with a cover sheet that
blocks out all but one selected color swatch and the human
will NO LONGER see the same colors when the lighting is
changed. This proved that the human vision system uses the
reflections from nearby areas to help adduce any nearby
color. As the reflections shift dramatically for one color
swatch, so it also shifts for others nearby. Lose that
additional information source and the brain can't maintain
the perception. Keep it, and it can.

Edwin Land spent years studying this phenomenon well after
both CIE standards groups put out their results and it turns
out that humans also use nearby colors to "calibrate" their
perceptions.

In any case, it is VERY illuminating to study this material
(the CIE _and_ Dr. Land research papers) and it _may_ bear on
this "issue." It made sense to me to at least ask if the OP
is fully familiar with the existing research here.

I spent some years working with OSRAM on these issues. I
worried that Charlie may be fighting an issue that might be
more easily 'understood' from a different domain. He is in a
better position to generally know one way or another, but a
small pointer might help if he wasn't already aware.

Jon
 
C

Charlie E.

Jan 1, 1970
0
Thanks. It was offered in that vein.

The funding of accurate human color perception _measurement_
dates back at least to the time when colored house paints
began to be sold (by Sears, for example) as something to
'spruce up' homes. (Turn of 19th to 20th century, roughly.)

Customers would buy a 'brown' for an addition, hoping to get
the same 'brown' they ordered two years before, and getting
something that 'any idiot' could see wasn't even close. The
control of paint chemicals and dyes wasn't sufficient by
itself at the time and there was a strong need for some
"feedback" to help adjust the dyes, as appropriate.

This commercial desire played into a university research
desire regarding color blindness and provided a substantial
funding source for this research to proceed.

A method was needed so that a 'brown' paint bought today and
used on the shady part of a home would look the same as the
same 'brown' paint bought next year and used on a well-lit
side. Side by side, the two paint jobs should "look the
same" to a viewer -- VERY WIDELY varying lighting conditions.

The CIE color system has remarkable fidelity for that
purpose. It also can deal with lighting conditions within
some limits.

What it does not do is cope with the surroundings, which in
human perception is very important. That is one reason why I
pointed him at Edwin Land and one reason why I wondered how
Charlie was determining when the color reading was wrong or
right.

If you take a canvas and place it on a painting easel and put
swatches of colors nearby each other on that canvas and light
it with a bright 100W tungsten bulb, people will see the
colors a certain way. Then, as you dim the bulb down, the
Planck radiation curve emitted will shift dramatically in
wavelength -- all of us here are well aware of this fact --
causing reflections and the resulting distribution of
wavelengths from the surfaces to be markedly different than
before. Yet even operating at 10W or even 1W of output, with
the distribution almost totally different than before, a
human will still "see" the same "colors."

Do the same experiment, now instead with a cover sheet that
blocks out all but one selected color swatch and the human
will NO LONGER see the same colors when the lighting is
changed. This proved that the human vision system uses the
reflections from nearby areas to help adduce any nearby
color. As the reflections shift dramatically for one color
swatch, so it also shifts for others nearby. Lose that
additional information source and the brain can't maintain
the perception. Keep it, and it can.

Edwin Land spent years studying this phenomenon well after
both CIE standards groups put out their results and it turns
out that humans also use nearby colors to "calibrate" their
perceptions.

In any case, it is VERY illuminating to study this material
(the CIE _and_ Dr. Land research papers) and it _may_ bear on
this "issue." It made sense to me to at least ask if the OP
is fully familiar with the existing research here.

I spent some years working with OSRAM on these issues. I
worried that Charlie may be fighting an issue that might be
more easily 'understood' from a different domain. He is in a
better position to generally know one way or another, but a
small pointer might help if he wasn't already aware.

Jon

Hi Jon,
Basically, yes, I am using my own eyes as a calibration source, sort
of...

Since I have chosen my illumination source, and RGB LED run one color
at a time, I am not dealing with different illumination sources. I am
also not trying to do high accuracy color determination, just red,
green, blue, orange, etc. My frustration is that two units,
apparently calibrated identically, will still see certain colors
differently. Trying to identify the source of the differences led me
to consult with my friends here to see if there was some electronic
design error on my part. I suspect that, such little things as
different alignments of the LED and PT, different arrangements of my
blocking black felt, and even temperature of the unit may be enough to
skew the results so that certain 'border' colors change nations, i.e
beige becomes pink, gold becomes orange, and blue becomes purple, or
blue green.

Fortunately, in my market, it appears that this is a conundrum that
hasn't really been solved yet! Some makers require a calibration
before every read. I think I may just ship what I have, and see if it
is useful enough at my price point, to make sales.

Charlie
 
S

Sjouke Burry

Jan 1, 1970
0
Charlie said:
cut
Basically, yes, I am using my own eyes as a calibration source, sort
of...

Since I have chosen my
Cut
Your eye's may be quite insufficient.
I compared some time ago with a college, we both had correct
color vision(according to some standard tests).
Then we used a little test device, with one halve circle true yellow
and another half circle you could adjust red and green to get the same
hue and intensity yellow.
Well.... My yellow was pale green-yellow according to my college,
and his yellow looked to me like orange.
So when you fiddle around with an rgb led, your eyesight is a
poor judge, and some hardware to test would be better.
 
J

Joerg

Jan 1, 1970
0
Charlie E. wrote:

[...]
Since I have chosen my illumination source, and RGB LED run one color
at a time, I am not dealing with different illumination sources. I am
also not trying to do high accuracy color determination, just red,
green, blue, orange, etc. My frustration is that two units,
apparently calibrated identically, will still see certain colors
differently. Trying to identify the source of the differences led me
to consult with my friends here to see if there was some electronic
design error on my part. I suspect that, such little things as
different alignments of the LED and PT, different arrangements of my
blocking black felt, and even temperature of the unit may be enough to
skew the results so that certain 'border' colors change nations, i.e
beige becomes pink, gold becomes orange, and blue becomes purple, or
blue green.

Did you turn the black level subtraction back on? Also, I think just
some felt inside a thin plastic enclosure isn't going to cut it, you
need at least foil underneath and then make sure that nothing in the
sensor area heats up too much.

Fortunately, in my market, it appears that this is a conundrum that
hasn't really been solved yet! Some makers require a calibration
before every read. I think I may just ship what I have, and see if it
is useful enough at my price point, to make sales.

Understandable but dangerous. At least I would compare it to other units
that are in the market. Serious egg in the face never really wipes off
clean in small markets, people remember. Best not to let that happen.
 
J

JosephKK

Jan 1, 1970
0
Charlie E. wrote:

[...]
Since I have chosen my illumination source, and RGB LED run one color
at a time, I am not dealing with different illumination sources. I am
also not trying to do high accuracy color determination, just red,
green, blue, orange, etc. My frustration is that two units,
apparently calibrated identically, will still see certain colors
differently. Trying to identify the source of the differences led me
to consult with my friends here to see if there was some electronic
design error on my part. I suspect that, such little things as
different alignments of the LED and PT, different arrangements of my
blocking black felt, and even temperature of the unit may be enough to
skew the results so that certain 'border' colors change nations, i.e
beige becomes pink, gold becomes orange, and blue becomes purple, or
blue green.

Did you turn the black level subtraction back on? Also, I think just
some felt inside a thin plastic enclosure isn't going to cut it, you
need at least foil underneath and then make sure that nothing in the
sensor area heats up too much.

Fortunately, in my market, it appears that this is a conundrum that
hasn't really been solved yet! Some makers require a calibration
before every read. I think I may just ship what I have, and see if it
is useful enough at my price point, to make sales.

Understandable but dangerous. At least I would compare it to other units
that are in the market. Serious egg in the face never really wipes off
clean in small markets, people remember. Best not to let that happen.

Of course some of that is in how it is marketed. If it is sold as right
often enough to be useful that is one thing, if it is marketed as
reliable and repeatable it is another.
 
J

Joerg

Jan 1, 1970
0
JosephKK said:
Charlie E. wrote:
[...]
Understandable but dangerous. At least I would compare it to other units
that are in the market. Serious egg in the face never really wipes off
clean in small markets, people remember. Best not to let that happen.

Of course some of that is in how it is marketed. If it is sold as right
often enough to be useful that is one thing, if it is marketed as
reliable and repeatable it is another.


Even in the first case it better be on par with simlarly priced other
units or better. I don't know the market for Charlie's device but it is
amazing how fast reputation is gained or lost with the Internet these
days. All it takes is a major blog somewhere.
 
C

Charlie E.

Jan 1, 1970
0
Charlie E. wrote:

[...]
Since I have chosen my illumination source, and RGB LED run one color
at a time, I am not dealing with different illumination sources. I am
also not trying to do high accuracy color determination, just red,
green, blue, orange, etc. My frustration is that two units,
apparently calibrated identically, will still see certain colors
differently. Trying to identify the source of the differences led me
to consult with my friends here to see if there was some electronic
design error on my part. I suspect that, such little things as
different alignments of the LED and PT, different arrangements of my
blocking black felt, and even temperature of the unit may be enough to
skew the results so that certain 'border' colors change nations, i.e
beige becomes pink, gold becomes orange, and blue becomes purple, or
blue green.

Did you turn the black level subtraction back on? Also, I think just
some felt inside a thin plastic enclosure isn't going to cut it, you
need at least foil underneath and then make sure that nothing in the
sensor area heats up too much.

Fortunately, in my market, it appears that this is a conundrum that
hasn't really been solved yet! Some makers require a calibration
before every read. I think I may just ship what I have, and see if it
is useful enough at my price point, to make sales.

Understandable but dangerous. At least I would compare it to other units
that are in the market. Serious egg in the face never really wipes off
clean in small markets, people remember. Best not to let that happen.

Hi Jeorge,
Yep, I turned on the black level subtraction (or, increased it to
match temporal conditions...) and it has helped some. Also, sensor is
in front of unit, power supplies are at least an inch away. I am more
concerned with the opamps and the digital pot maybe self heating,
especially when I have been testing for a while...

My real problem I think is engineer's disease... I keep thinking of
improvements to the hardware and software!

Charlie
 
C

Charlie E.

Jan 1, 1970
0
Charlie E. wrote:

[...]
Since I have chosen my illumination source, and RGB LED run one color
at a time, I am not dealing with different illumination sources. I am
also not trying to do high accuracy color determination, just red,
green, blue, orange, etc. My frustration is that two units,
apparently calibrated identically, will still see certain colors
differently. Trying to identify the source of the differences led me
to consult with my friends here to see if there was some electronic
design error on my part. I suspect that, such little things as
different alignments of the LED and PT, different arrangements of my
blocking black felt, and even temperature of the unit may be enough to
skew the results so that certain 'border' colors change nations, i.e
beige becomes pink, gold becomes orange, and blue becomes purple, or
blue green.

Did you turn the black level subtraction back on? Also, I think just
some felt inside a thin plastic enclosure isn't going to cut it, you
need at least foil underneath and then make sure that nothing in the
sensor area heats up too much.

Fortunately, in my market, it appears that this is a conundrum that
hasn't really been solved yet! Some makers require a calibration
before every read. I think I may just ship what I have, and see if it
is useful enough at my price point, to make sales.

Understandable but dangerous. At least I would compare it to other units
that are in the market. Serious egg in the face never really wipes off
clean in small markets, people remember. Best not to let that happen.

Of course some of that is in how it is marketed. If it is sold as right
often enough to be useful that is one thing, if it is marketed as
reliable and repeatable it is another.

Exactly. Most of the products out there now in this market are in the
'right enough to be useful' category. What is interesting is some of
the more expensive units, where you could buy a calibrated colorimeter
for less...

Charlie
 
J

Joerg

Jan 1, 1970
0
Charlie said:
Charlie E. wrote:

[...]
Since I have chosen my illumination source, and RGB LED run one color
at a time, I am not dealing with different illumination sources. I am
also not trying to do high accuracy color determination, just red,
green, blue, orange, etc. My frustration is that two units,
apparently calibrated identically, will still see certain colors
differently. Trying to identify the source of the differences led me
to consult with my friends here to see if there was some electronic
design error on my part. I suspect that, such little things as
different alignments of the LED and PT, different arrangements of my
blocking black felt, and even temperature of the unit may be enough to
skew the results so that certain 'border' colors change nations, i.e
beige becomes pink, gold becomes orange, and blue becomes purple, or
blue green.
Did you turn the black level subtraction back on? Also, I think just
some felt inside a thin plastic enclosure isn't going to cut it, you
need at least foil underneath and then make sure that nothing in the
sensor area heats up too much.

Fortunately, in my market, it appears that this is a conundrum that
hasn't really been solved yet! Some makers require a calibration
before every read. I think I may just ship what I have, and see if it
is useful enough at my price point, to make sales.
Understandable but dangerous. At least I would compare it to other units
that are in the market. Serious egg in the face never really wipes off
clean in small markets, people remember. Best not to let that happen.

Hi Jeorge,
Yep, I turned on the black level subtraction (or, increased it to
match temporal conditions...) and it has helped some. Also, sensor is
in front of unit, power supplies are at least an inch away. I am more
concerned with the opamps and the digital pot maybe self heating,
especially when I have been testing for a while...

Opamps can be covered, either by using low offset versions or by
old-fashioned clamping. Digital potmeters, different thing. One can
never rely on the absolute value. The step-to-step accuracy would be
listed in the datasheets and if that ain't good enough you'd have to
develop a solution without those potmeters.

But I'd also be concerned about IR getting inside. Your photodiode isn't
so stellar in rejecting near-IR and without metal between plastic and
felt your box may let a lot of that pass through.

My real problem I think is engineer's disease... I keep thinking of
improvements to the hardware and software!

Don't we all :)

Just like the typical SW/firmware guy won't stop until 95% plus of the
available ROM space is filled.
 
C

Charlie E.

Jan 1, 1970
0
Charlie said:
Charlie E. wrote:

[...]

Since I have chosen my illumination source, and RGB LED run one color
at a time, I am not dealing with different illumination sources. I am
also not trying to do high accuracy color determination, just red,
green, blue, orange, etc. My frustration is that two units,
apparently calibrated identically, will still see certain colors
differently. Trying to identify the source of the differences led me
to consult with my friends here to see if there was some electronic
design error on my part. I suspect that, such little things as
different alignments of the LED and PT, different arrangements of my
blocking black felt, and even temperature of the unit may be enough to
skew the results so that certain 'border' colors change nations, i.e
beige becomes pink, gold becomes orange, and blue becomes purple, or
blue green.

Did you turn the black level subtraction back on? Also, I think just
some felt inside a thin plastic enclosure isn't going to cut it, you
need at least foil underneath and then make sure that nothing in the
sensor area heats up too much.


Fortunately, in my market, it appears that this is a conundrum that
hasn't really been solved yet! Some makers require a calibration
before every read. I think I may just ship what I have, and see if it
is useful enough at my price point, to make sales.

Understandable but dangerous. At least I would compare it to other units
that are in the market. Serious egg in the face never really wipes off
clean in small markets, people remember. Best not to let that happen.

Hi Jeorge,
Yep, I turned on the black level subtraction (or, increased it to
match temporal conditions...) and it has helped some. Also, sensor is
in front of unit, power supplies are at least an inch away. I am more
concerned with the opamps and the digital pot maybe self heating,
especially when I have been testing for a while...

Opamps can be covered, either by using low offset versions or by
old-fashioned clamping. Digital potmeters, different thing. One can
never rely on the absolute value. The step-to-step accuracy would be
listed in the datasheets and if that ain't good enough you'd have to
develop a solution without those potmeters.

But I'd also be concerned about IR getting inside. Your photodiode isn't
so stellar in rejecting near-IR and without metal between plastic and
felt your box may let a lot of that pass through.

My real problem I think is engineer's disease... I keep thinking of
improvements to the hardware and software!

Don't we all :)

Just like the typical SW/firmware guy won't stop until 95% plus of the
available ROM space is filled.

Hey, I am at 96%! Maybe I can ship now... ;-)

Charlie
 
C

Charlie E.

Jan 1, 1970
0
Well, it looks like it is time to call it a day. I spent two days
this weekend testing, and calibrating four units. On the bench, they
all worked great, and gave good results across my entire test samples.

This morning, I mounted them in their final cases, and hooked them up.
Two failed immediately, basically decided everything I tested was
white. Two appeared to function, but as soon as I started testing,
failed on every 'corner' case in my test samples. Took one of those
back to the bench, and the calibrations had shifted drastically. Funny
thing was, the shift was to needing more gain, not less, which the
'all white' indications would have indicated.

Technically, I have been 'measuring' gain as the setting on the
digital pot that gave an almost full indications on the ADC. This
gave me values from 0 to 255. When I measured this unit on Saturday,
it had gains of red 239, green 239 and blue 226. On Sunday, when I
finallized the program, it read 231, 233, 214. This morning, after
retesting, it calibrates at 245, 241, and 231. So, a shift of over 5%
in just two days. There might have been temperature or background
variations, but the background measuremnts have been stable at a
reading of around 8 - 10 on a scale of 2048. I am totally baffled!

So, after a year and about $2000 in materials, looks we are going to
forget this product, unless some of ya'll have any ideas.

Anyone out there know of anyone needing a good applications engineer?

Charlie
 
J

Joerg

Jan 1, 1970
0
Charlie said:
Well, it looks like it is time to call it a day. I spent two days
this weekend testing, and calibrating four units. On the bench, they
all worked great, and gave good results across my entire test samples.

This morning, I mounted them in their final cases, and hooked them up.
Two failed immediately, basically decided everything I tested was
white. Two appeared to function, but as soon as I started testing,
failed on every 'corner' case in my test samples. Took one of those
back to the bench, and the calibrations had shifted drastically. Funny
thing was, the shift was to needing more gain, not less, which the
'all white' indications would have indicated.

Technically, I have been 'measuring' gain as the setting on the
digital pot that gave an almost full indications on the ADC. This
gave me values from 0 to 255. When I measured this unit on Saturday,
it had gains of red 239, green 239 and blue 226. On Sunday, when I
finallized the program, it read 231, 233, 214. This morning, after
retesting, it calibrates at 245, 241, and 231. So, a shift of over 5%
in just two days. There might have been temperature or background
variations, but the background measuremnts have been stable at a
reading of around 8 - 10 on a scale of 2048. I am totally baffled!

So, after a year and about $2000 in materials, looks we are going to
forget this product, unless some of ya'll have any ideas.

Nah, don't throw in the towel so fast :)

Something is deteriorating. Assuming VCC is perfectly stable (check for
dips with a DSO) this almost has to be the LEDs.

Question: How close to the max do you drive your LEDs? If in a healthy
range hang a scope across RLED and check for fast spikes. I am not at
all a fan of charge pump converters, who knows, maybe it's kicking out
nasty ones.

Does your software turn LED_PWR_ON to off before changing position at
the BSS8402 switches and then back on? It should, because the regulator
will not be able to react in nanoseconds, it'll be more in the tens of
microseconds.

Anyone out there know of anyone needing a good applications engineer?

Sorry, I don't. We were looking for an analog guy at a client but that's
been filled by now.
 
C

Charlie E.

Jan 1, 1970
0
Nah, don't throw in the towel so fast :)

Something is deteriorating. Assuming VCC is perfectly stable (check for
dips with a DSO) this almost has to be the LEDs.

Question: How close to the max do you drive your LEDs? If in a healthy
range hang a scope across RLED and check for fast spikes. I am not at
all a fan of charge pump converters, who knows, maybe it's kicking out
nasty ones.

Does your software turn LED_PWR_ON to off before changing position at
the BSS8402 switches and then back on? It should, because the regulator
will not be able to react in nanoseconds, it'll be more in the tens of
microseconds.



Sorry, I don't. We were looking for an analog guy at a client but that's
been filled by now.

Thanks, Jeorg,
I am driving the LEDs at 20mA, which might be the problem if there are
spikes that drive it above limits. I did think to turn the power off
before switching. I even turned one LED on, then turned the other off
for a while, to be sure there were not any no load conditions on the
switcher. I don't have an o-scope at this time. It was on my list
for purchases as soon as we made some sales... ;-)

I wish I was an analog guy, but this project has shown me how far I
have to go to really consider myself to have the necessary experience
to be one!

Charlie
 
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