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dannylsmith
Joined: 21 Feb 2006
Posts: 9
Location: Panama City Beach, FL
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 Posted: Wed Apr 16, 2008 8:04 am Post subject: Voltage Drop in DM15-14 Dimmer |
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I have the DM15-14 dimmer with only a Garmin GMA-340, TT ADI and a 3 ft LED
strip (.086amp) attached to it.
When I turned on the LED strip it didn't seem very bright so I checked the
voltage and found that with an
input to the dimmer of 12.7 V the output was only 9.7 V. Is a 3 V drop to be
expected or is the dimmer
module defective?
Danny
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Danny |
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nuckolls.bob(at)cox.net
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| Posted: Wed Apr 16, 2008 1:17 pm Post subject: Voltage Drop in DM15-14 Dimmer |
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At 11:01 AM 4/16/2008 -0500, you wrote:
| Quote: |
<dsmit132(at)bellsouth.net>
I have the DM15-14 dimmer with only a Garmin GMA-340, TT ADI and a 3 ft LED
strip (.086amp) attached to it.
When I turned on the LED strip it didn't seem very bright so I checked the
voltage and found that with an
input to the dimmer of 12.7 V the output was only 9.7 V. Is a 3 V drop to be
expected or is the dimmer
module defective?
|
It's probably okay. The regulator used in those dimmers is
one of the LM317 series devices. You can get the data sheet
at:
http://cache.national.com/ds/LM/LM117.pdf
the figure on page 6 labeled "Dropout Votlage"
tells us that the minimum input-output differential
can be as high as 2.0 volts depending on load.
I had a number of folks question the voltage
drop at max intensity settings . . . if it's
a valid concern, there are other devices that
offer reduced overhead maximums.
When I designed those dimmers, the goal was
(1) provide control of virtually any size illumination
load by means of a small, panel friendly control
potentiometer and (2) offer good voltage regulation
such that bus voltage perturbations didn't show
up in the panel lighting. An ancillary consideration
was that 98+ percent of dimmer operations were at
very low output settings . . . on the order of 4-6
volts.
The duration of flight time where visibility
of the illuminated objects would be enhanced
by raising the dimmer from say 11 to 14 volts
is a very few minutes during the day-night
transition. Hence, limiting maximum output to
2 volts or so below bus voltage was not a big
deal.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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