Wat-temp, VARIABLE LED output
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--- In basicstamps@yahoogroups.com, Nigel Emms <rulingshogun@y...>
wrote:
> --- sunvalleyhouse <sunvalleyhouse@y...> wrote:
> > Folks,
> >
> > I need to read water temperature, and then vary the
> intensity of an LED based on the value. To complicate
> matters, I need to light 3 different color LEDs
> representing discrete temperature bands.
>
> When I have used circuits that vary the intensity of
> an LED I have been very dissapointed that are not as
> noticable as when using a regular bulb. I would
> suggest an LED ladder ie: 1 LED on for low, 2 LEDs on
> for mid range 3 LEDS on for high, might give a more
> satisfactory results.
>
> For what it is worth, Nigel
True, true.
One can run PWM to an led with 50mA to get a much brighter light (the
duty cycle of 50mA CANNOT exceed the 20mA rating of the device.
So, you can get a brighter light, and you can dim it. but there are
problems with trying to determine if the LED is half bright or if
your eyes are suffering from too much ALE or too much sunshine.
There are dozens of ways to relay the information. you can light one
color to indicate a range, and another to indicate it is 1/4 between
that range and the next so your 3 lights can represent about 16 steps
with only useing a simple fast flash, slow flash and another LED.
Of course numeric displays are not that hard and will offer numerical
values.
The PROBLEM with those is that they need to be calibrated and that
can be hard to do. ie: when it reads 100, how do you know it is 100
and not 95 or 105 ?
Dave
>
>
>
>
> __________________________________
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wrote:
> --- sunvalleyhouse <sunvalleyhouse@y...> wrote:
> > Folks,
> >
> > I need to read water temperature, and then vary the
> intensity of an LED based on the value. To complicate
> matters, I need to light 3 different color LEDs
> representing discrete temperature bands.
>
> When I have used circuits that vary the intensity of
> an LED I have been very dissapointed that are not as
> noticable as when using a regular bulb. I would
> suggest an LED ladder ie: 1 LED on for low, 2 LEDs on
> for mid range 3 LEDS on for high, might give a more
> satisfactory results.
>
> For what it is worth, Nigel
True, true.
One can run PWM to an led with 50mA to get a much brighter light (the
duty cycle of 50mA CANNOT exceed the 20mA rating of the device.
So, you can get a brighter light, and you can dim it. but there are
problems with trying to determine if the LED is half bright or if
your eyes are suffering from too much ALE or too much sunshine.
There are dozens of ways to relay the information. you can light one
color to indicate a range, and another to indicate it is 1/4 between
that range and the next so your 3 lights can represent about 16 steps
with only useing a simple fast flash, slow flash and another LED.
Of course numeric displays are not that hard and will offer numerical
values.
The PROBLEM with those is that they need to be calibrated and that
can be hard to do. ie: when it reads 100, how do you know it is 100
and not 95 or 105 ?
Dave
>
>
>
>
> __________________________________
> Do you Yahoo!?
> Friends. Fun. Try the all-new Yahoo! Messenger.
> http://messenger.yahoo.com/