Re: Anotehr Basic Q. re: a circuit

Kris Krieger wrote:
"Phil Allison" <philallison@xxxxxxxxxx> wrote in
news:6fnev2Fcg4atU1@xxxxxxxxxxxxxxxxxx:

"Kris Krieger"
"Phil Allison"
Sorry for another stupid question, but, I'm looking at this
http://www.maxim-ic.com/appnotes.cfm/an_pk/1750
and can't figure out whether I can ignore, or whether I need to add
in some
modification of something like this
http://www.instructables.com/id/S8Q5N9QFHTAIQK7/
where the first diagram says
" PWM Dimming 0 to 3.3HZ f>15KHz 0%=shdn 100%=20mA "

A clue would be appreciated - especially since I don't know whetehr
they mean dimming as in a Dimmer Switch on a lamp, or whether they
mean something entirely different...

** The CTRL input operates to dim the LEDs with a 0 to 3.3 volts
variable DC input, which can be created by filtering a PWM signal
as shown or any other way you like - eg with a 3.3 volt supply and
a pot.

In the Data*** for the IC, in the chart describing the Pins, for
CTRL, it
says:
"Brightness/Shutdown dualmode control input. LED brightness and IC
shutdown are controlled by the voltage on CTRL. VOltage between
250mV and 5.5V or (V+ + 2V), whichever is less, adjust the brightness
from dim to bright, respectively. To put the IC into shutdown, drive
below 100mV or connect to GRND."

So, for a low-voltage light (2 or three 1.2V NiMH batteries, 1500mA
to 2500mA), that means it's jsut personal choice rather than
mandatory to add in the dimmer?, IOW, I can either add in a dimmer,
or just connect the pin to the ground/out terminal?

** Why are YOU crapping on about adding a " dimmer " all the time ??

That IC has a built in dimming function which operates as stated.


Because I'm teaching myself, and I didn't understand that - the diagram showed it connecting to something, and I didn't understand what that "something" is. To me, it looked like some separate IC or circuit becasue, if it was suposed to just be connected to teh ground, I assume it would have shown the symbol for that, rather than a circle. Now, if sci.electronics.basics is not the place to ask basic questions, please let me know what would be a more appropriate venue for people who are trying to learn on their own and have similarly-basic questions, and I'll be glad go to that NG (or forum) instead.

Yes this is the right group.

One of the basics of learning from newsgroups is that you'll get some very negative emotions in your responses, sometimes.

If you get on to google groups and read a sampling of Phil's posts you'll realize that this one is really quite positive.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
.