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aslsa.rng(at)gmail.com
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 Posted: Wed Aug 27, 2008 10:35 am Post subject: Voltage dropping resistor calculations |
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Okay guys take it esy on the electrically ignorant. I have a Lowrance 2000C GPS in my trike that just eats batteries. I get about an hour from 4 new AA's. It was no problem when I was only flying that long one way, I'd just carry four spares in my pocket and change them out before starting home. When I started going further afield I decided to use one of the open slots on the fuse panel and power it from ship's power instead. Since I had the lighter cord that came with the GPS but no lighter recepticle on the trike, I cut off the lighter plug, put on a couple of fastons on the ends of the wires and was FD & H for the last year. I should add that I was smart enough to look at the innards of the plug just to make sure there wasn't anything inside that looked critical to powering the unit. There was one small resistor, but it seemed to me it was for the LED and not the GPS. It was while going through the manual some thirty hours since making the change to onboard power that I began to worry there is no universal power adapter built into the GPS. I fear that I may be pumping 12V into a 6V power supply.
This morning I pulled the + wire at the fuse panel and measured the current draw at just slightly under .6 amps. If I understand Ohm's law, and there's some doubt in my mind about that, I need a 10 ohm resistor to drop the voltage, so a stop at Rat Shack was in order. I now have a pair of 10 ohm 1 watt resistors, and two questions.
Did I do the math correctly? Am I worrying about nothing? Seems to me the GPS runs through the lighter cord just fine on 12 volts, but I sure would hate to damage it by being stupid.
Thanks,
Rick Girard
[quote][b]
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jon(at)finleyweb.net
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| Posted: Wed Aug 27, 2008 11:03 am Post subject: Voltage dropping resistor calculations |
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Fear not Rick, you are ok. I too have the 2000c wired directly into my 12V bus. I don't remember the exact specs but the unit is very tolerant of voltage. Seems like it was anything from 6 to 24 volts (or something like that - check the documentation to confirm).
Also, if you install a resistor, the 2000c's voltage display will no longer represent what is on the ship's bus. This is not my primary voltage display but it is a nice backup.
Jon
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nuckolls.bob(at)cox.net
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| Posted: Wed Aug 27, 2008 12:01 pm Post subject: Voltage dropping resistor calculations |
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At 01:33 PM 8/27/2008 -0500, you wrote:
| Quote: | Okay guys take it esy on the electrically ignorant. I have a Lowrance
2000C GPS in my trike that just eats batteries. I get about an hour from 4
new AA's. It was no problem when I was only flying that long one way, I'd
just carry four spares in my pocket and change them out before starting
home. When I started going further afield I decided to use one of the open
slots on the fuse panel and power it from ship's power instead. Since I
had the lighter cord that came with the GPS but no lighter recepticle on
the trike, I cut off the lighter plug, put on a couple of fastons on the
ends of the wires and was FD & H for the last year. I should add that I
was smart enough to look at the innards of the plug just to make sure
there wasn't anything inside that looked critical to powering the unit.
There was one small resistor, but it seemed to me it was for the LED and
not the GPS. It was while going through the manual some thirty hours since
making the change to onboard power that I began to worry there is no
universal power adapter built into the GPS. I fear that I may be pumping
12V into a 6V power supply.
This morning I pulled the + wire at the fuse panel and measured the
current draw at just slightly under .6 amps. If I understand Ohm's law,
and there's some doubt in my mind about that, I need a 10 ohm resistor to
drop the voltage, so a stop at Rat Shack was in order. I now have a pair
of 10 ohm 1 watt resistors, and two questions.
Did I do the math correctly? Am I worrying about nothing? Seems to me the
GPS runs through the lighter cord just fine on 12 volts, but I sure would
hate to damage it by being stupid.
|
Hmmmm . . . if this was the cord supplied with the
unit, it seems that it SHOULD run on 12v . . . however,
the manual I found at:
http://www.lowrance.com/upload/Lowrance/Documents/Manuals/airMap2000c_0148-471_080504.pdf
page 11 says it runs on 6v using an external power cord
with cigar lighter adapter. This implies to me that the
power cord has a 14v to 6v down converter.
Recommend you do not use a resistor . . . too much
voltage variation with respect to current draw. Further,
the resistor would dissipate .6 at 6 to 8 volts for
a maximum of 5w . . . pretty warm for your 1 watt
devices. Better to craft a voltage regulator that
is not unlike the little variable dimmer supplies
we used to offer . . . and B&C still does. You can
get the parts at RS and wire like:
http://www.aeroelectric.com/articles/Dimmers/9013_Ins.pdf
In this case, you would replace the 910 ohm resistor
with a 1500 ohm resistor and just run it to ground
instead of taking it off the board to a control pot.
We'll be offering a filtered, regulated, step-down
supply that's jumper selectable for 9, 7.5, 6, 4.5 and
3 volts. If you're not in a big hurry, you can have
the proof-of-concept model. Probably late next week.
It's 2.1 x 2.1 inches footprint an looks like this
critter . . .
http://www.aeroelectric.com/Catalog/AEC/9006/9006-800-2.jpg
except that it will have metal mounting base and
a small array of jumper pins on top to select one
of 5 operating voltages.
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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klehman(at)albedo.net
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| Posted: Wed Aug 27, 2008 1:11 pm Post subject: Voltage dropping resistor calculations |
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I think Jon is right and you are fine. If there was any kind of voltage
dropping in the plug it would get noticeably warm like my cell phone
plug and I've never noticed the 2000c plug to get warm. And as mentioned
the 2000c will display the correct system voltage of 14.3 when I look.
Also notice that the display dims noticeably on 6v battery power
compared to using 12 volts and I believe the manual says that is normal.
The only batteries worth putting in my unit are 2000mah or larger NiMh.
Alkaline life seems to be measured in minutes. The black and white
model is much more battery friendly.
Ken
jon(at)finleyweb.net wrote:
[quote] Fear not Rick, you are ok. I too have the 2000c wired directly into my
12V bus. I don't remember the exact specs but the unit is very tolerant
of voltage. Seems like it was anything from 6 to 24 volts (or something
like that - check the documentation to confirm).
Also, if you install a resistor, the 2000c's voltage display will no
longer represent what is on the ship's bus. This is not my primary
voltage display but it is a nice backup.
Jon
--
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jindoguy(at)gmail.com
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| Posted: Thu Aug 28, 2008 1:04 pm Post subject: Voltage dropping resistor calculations |
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Ken, it was that note about 6 volts that led me to wonder about appropriate voltage. I called the factory this afternoon and told the tech I wanted to wire my 2000C into ship's power. She told me to snip off the lighter plug and wire away. The internal power supply can handle up to 36V input. Thanks to all who replied, this list is a great resource.
Say Bob, I live just down the road in Udall. Would you like to go for a ride in the trike some evening and see what cruising at 42 mph is like. I have training bars (not wheels) on the big wing so you can have the PIC station and really see what weight shift control aircraft are about.
Rick
On Wed, Aug 27, 2008 at 4:11 PM, Ken <klehman(at)albedo.net (klehman(at)albedo.net)> wrote:
[quote] --> AeroElectric-List message posted by: Ken <klehman(at)albedo.net (klehman(at)albedo.net)>
I think Jon is right and you are fine. If there was any kind of voltage dropping in the plug it would get noticeably warm like my cell phone plug and I've never noticed the 2000c plug to get warm. And as mentioned the 2000c will display the correct system voltage of 14.3 when I look. Also notice that the display dims noticeably on 6v battery power compared to using 12 volts and I believe the manual says that is normal.
The only batteries worth putting in my unit are 2000mah or larger NiMh. Alkaline life seems to be measured in minutes. The black and white model is much more battery friendly.
Ken
jon(at)finleyweb.net (jon(at)finleyweb.net) wrote:
[quote] Fear not Rick, you are ok. I too have the 2000c wired directly into my 12V bus. I don't remember the exact specs but the unit is very tolerant of voltage. Seems like it was anything from 6 to 24 volts (or something like that - check the documentation to confirm).
Also, if you install a resistor, the 2000c's voltage display will no longer represent what is on the ship's bus. This is not my primary voltage display but it is a nice backup.
Jon
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nuckolls.bob(at)cox.net
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| Posted: Thu Aug 28, 2008 4:34 pm Post subject: Voltage dropping resistor calculations |
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At 04:01 PM 8/28/2008 -0500, you wrote:
| Quote: | Ken, it was that note about 6 volts that led me to wonder about
appropriate voltage. I called the factory this afternoon and told the tech
I wanted to wire my 2000C into ship's power. She told me to snip off the
lighter plug and wire away. The internal power supply can handle up to 36V
input. Thanks to all who replied, this list is a great resource.
|
I was wondering about that. Given that you'd already tried
it without getting smoke suggested that the power conditioning
had a pretty wide input range!
| Quote: | Say Bob, I live just down the road in Udall. Would you like to go for a
ride in the trike some evening and see what cruising at 42 mph is like. I
have training bars (not wheels) on the big wing so you can have the PIC
station and really see what weight shift control aircraft are about.
Rick
|
I'd like that! Do you live on the community grass strip south
of the city?
If so, do the Randalls still live there? I used to deliver
papers to the older Randall when I was in high school.
Randall the younger was really into rebuilding wrecked
cars. Was quite a craftsman as I recall. Last I heard of
them was a move to the airport south of Udall where I
think they took up some aircraft maintenance and rebuilding.
Bob . . .
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jindoguy(at)gmail.com
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| Posted: Thu Aug 28, 2008 5:52 pm Post subject: Voltage dropping resistor calculations |
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Bob, That's where I am. Tom Randall lives just up the road. I've never seen an airplane at his place except for transients and when we run Young Eagles flights during the Udall Fall Festival. He does a lot of big vehicles and cars, though.
How close are you to Benton (1K1) or Jabara (AAO)? That's an easy cruise in the trike when the big wing is on. Since we have a long weekend coming up we could try for a morning flight before the convective activity kicks off. That way if there's any headwind I don't have to worry about running out of daylight while trying to get home.
Rick
On Thu, Aug 28, 2008 at 7:33 PM, Robert L. Nuckolls, III <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)> wrote:
[quote] --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)>
At 04:01 PM 8/28/2008 -0500, you wrote:
| Quote: | Ken, it was that note about 6 volts that led me to wonder about appropriate voltage. I called the factory this afternoon and told the tech I wanted to wire my 2000C into ship's power. She told me to snip off the lighter plug and wire away. The internal power supply can handle up to 36V input. Thanks to all who replied, this list is a great resource.
|
I was wondering about that. Given that you'd already tried
it without getting smoke suggested that the power conditioning
had a pretty wide input range!
| Quote: | Say Bob, I live just down the road in Udall. Would you like to go for a ride in the trike some evening and see what cruising at 42 mph is like. I have training bars (not wheels) on the big wing so you can have the PIC station and really see what weight shift control aircraft are about.
Rick
|
I'd like that! Do you live on the community grass strip south
of the city?
If so, do the Randalls still live there? I used to deliver
papers to the older Randall when I was in high school.
Randall the younger was really into rebuilding wrecked
cars. Was quite a craftsman as I recall. Last I heard of
them was a move to the airport south of Udall where I
think they took up some aircraft maintenance and rebuilding.
Bob . . .
[b]
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