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SA Development
Guest
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 Posted:
Fri Mar 11, 2005 2:09 am Post subject:
Can someone point me to an efficient easy to make led circui |
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Hi,
I need to have a regular LED (doesn't need to be anything special like a
superbright LED) stay lit as long as possible on either a single D cell or
two D cells. D cells are rated for about 20.5A if used down to 0.8V. I'm
assuming I would need some sort of regulator to do this... I think a
regular LED is 20ma forward voltage 1.9v ?...
Thanks,
SA Dev
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PeteS
Guest
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| Posted:
Fri Mar 11, 2005 5:19 pm Post subject:
Re: Can someone point me to an efficient easy to make led ci |
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You are corect in the forward voltage assumption. Note, however, that
different colours have different forward voltages. Most green, red and
yellow (amber) LEDs are in the range of 1.6-2V when fully on.
If you don't need much current (you don't), you could use a switched
capacitor boost driver, or even a flying capacitor device. These things
are all over the place - look at Maxim (http://www.maxim-ic.com),
National Semiconductor (http://www.national.com) and Linear technology
(http://www.linear.com) for typical devices.
Cheers
PeteS |
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dB
Guest
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| Posted:
Fri Mar 11, 2005 10:08 pm Post subject:
Re: Can someone point me to an efficient easy to make led ci |
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"SA Development" <nospam38925@forme.com> wrote
| Quote: | I need to have a regular LED (doesn't need to be anything special like a
superbright LED) stay lit as long as possible on either a single D cell or
two D cells. D cells are rated for about 20.5A if used down to 0.8V. I'm
assuming I would need some sort of regulator to do this... I think a
regular LED is 20ma forward voltage 1.9v ?...
|
You will need two, not one, cell.
Experiment with values of series resistor, and choose the highest
value which will give you an acceptable light intensity.
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PeteS
Guest
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| Posted:
Fri Mar 11, 2005 10:48 pm Post subject:
Re: Can someone point me to an efficient easy to make led ci |
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This can be done with one cell if a switched capacitor boost regulator
is used. One might even use a low power/low voltage RS232 converter
from maxim (output typically +/-5V).
Cheers
PeteS |
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