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charlieray(at)optonline.n
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 Posted: Sat Jan 20, 2007 6:41 am Post subject: Basis wiring HELP |
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Dana,
The main problem with Bright/Dim kind of circuits is that you have to know
the over all current flow for all the lights per circuit. If you go and
change something in the future of one set of bulbs burn out, it changes your
total brightness on the dim setting. You do this with the basic V=IR
equation, you have to know the total current flow of your lights when hooked
to your power source. Here is an example. I hook all my lights to a power
supply that can give me my "running" voltage of about 13.85 volts when the
airplane is running, with an ammeter inline I measure 2 amps of lighting
load..... 13.85 xI Solving for I you get 6.925 Ohms. This is the basic
resistance of all your lights put together. To make the lights half dim,
you need to make the resistance twice that of what you start with. So you
need a 7 ohm resistor that is rated for, P=IE..... P= 2x13.85 so roughly 30
Watts!!! Thats kind of a LARGE resistor. and its there under your panel in
a small place baking away making heat. I would suggest researching
Transistorized dimming circuits like the one here that EDMO dealers sell.
http://www.edmo.com/index.php?module=products&func=display&prod_id=18485
I know you are pressed for time and have put all the HARD parts off till the
last minute  but I think you will find a variable dimming system will make
your night flying much more enjoyable.
An appropriately rated rehostat will dissapate power (again a heat machine
under your panel) and something like this may be what you want...
http://www.aircraftspruce.com/catalog/elpages/rheostat.php
put a on off switch ahead of this sucker so its not contantly making heat
when you have the lights off.
http://www.aircraftspruce.com/catalog/elpages/lc40.php
This system looks nice due to its 4 channels of 1.5A each that can be tied
together and controlled with one knob.
I suggest keeping radios separate from flight instruments due to variations
in overall brightness.
http://www.aircraftspruce.com/catalog/elpages/k11aircraft.php
This one has an adjustable master following system where you can have those
bright systems lag behind say the less bright flight instruments.
Hope some of this helps.
Charles Reiche
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sportav8r(at)gmail.com
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| Posted: Sat Jan 20, 2007 9:23 am Post subject: Basis wiring HELP |
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A diode differs from a resistor in this application; the forward drop
in voltage across a diode is virtually constant regardless of current
draw. As long as diode current ratings are followed, there will not
be excessive heating of the diode in this application (similar to the
wattage rating of a resistor, but you have to know the final current
ahead of time to size one of those.)
Just more to think about.
-Bill
On 1/20/07, Charles Reiche <charlieray(at)optonline.net> wrote:
[quote]
Dana,
The main problem with Bright/Dim kind of circuits is that you have to know
the over all current flow for all the lights per circuit. If you go and
change something in the future of one set of bulbs burn out, it changes your
total brightness on the dim setting. You do this with the basic V=IR
equation, you have to know the total current flow of your lights when hooked
to your power source. Here is an example. I hook all my lights to a power
supply that can give me my "running" voltage of about 13.85 volts when the
airplane is running, with an ammeter inline I measure 2 amps of lighting
load..... 13.85 xI Solving for I you get 6.925 Ohms. This is the basic
resistance of all your lights put together. To make the lights half dim,
you need to make the resistance twice that of what you start with. So you
need a 7 ohm resistor that is rated for, P=IE..... P= 2x13.85 so roughly 30
Watts!!! Thats kind of a LARGE resistor. and its there under your panel in
a small place baking away making heat. I would suggest researching
Transistorized dimming circuits like the one here that EDMO dealers sell.
http://www.edmo.com/index.php?module=products&func=display&prod_id=18485
I know you are pressed for time and have put all the HARD parts off till the
last minute but I think you will find a variable dimming system will make
your night flying much more enjoyable.
An appropriately rated rehostat will dissapate power (again a heat machine
under your panel) and something like this may be what you want...
http://www.aircraftspruce.com/catalog/elpages/rheostat.php
put a on off switch ahead of this sucker so its not contantly making heat
when you have the lights off.
http://www.aircraftspruce.com/catalog/elpages/lc40.php
This system looks nice due to its 4 channels of 1.5A each that can be tied
together and controlled with one knob.
I suggest keeping radios separate from flight instruments due to variations
in overall brightness.
http://www.aircraftspruce.com/catalog/elpages/k11aircraft.php
This one has an adjustable master following system where you can have those
bright systems lag behind say the less bright flight instruments.
Hope some of this helps.
Charles Reiche
---
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
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retasker(at)optonline.net
Guest
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| Posted: Sat Jan 20, 2007 10:22 am Post subject: Basis wiring HELP |
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Actually, for the same voltage drop and the same current draw there WILL
be exactly the same heating of the diodes, albeit spread over all the
diodes used vs the one resistor used.
Diodes do have the advantage you pointed out of having a relatively
constant voltage drop up to their rated current.
Dick Tasker
Bill Boyd wrote:
[quote]
A diode differs from a resistor in this application; the forward drop
in voltage across a diode is virtually constant regardless of current
draw. As long as diode current ratings are followed, there will not
be excessive heating of the diode in this application (similar to the
wattage rating of a resistor, but you have to know the final current
ahead of time to size one of those.)
Just more to think about.
-Bill
On 1/20/07, Charles Reiche <charlieray(at)optonline.net> wrote:
>
>
> Dana,
> The main problem with Bright/Dim kind of circuits is that you have to
> know
> the over all current flow for all the lights per circuit. If you go and
> change something in the future of one set of bulbs burn out, it
> changes your
> total brightness on the dim setting. You do this with the basic V=IR
> equation, you have to know the total current flow of your lights when
> hooked
> to your power source. Here is an example. I hook all my lights to a
> power
> supply that can give me my "running" voltage of about 13.85 volts
> when the
> airplane is running, with an ammeter inline I measure 2 amps of lighting
> load..... 13.85 xI Solving for I you get 6.925 Ohms. This is the basic
> resistance of all your lights put together. To make the lights half
> dim,
> you need to make the resistance twice that of what you start with. So
> you
> need a 7 ohm resistor that is rated for, P=IE..... P= 2x13.85 so
> roughly 30
> Watts!!! Thats kind of a LARGE resistor. and its there under your
> panel in
> a small place baking away making heat. I would suggest researching
> Transistorized dimming circuits like the one here that EDMO dealers
> sell.
> http://www.edmo.com/index.php?module=products&func=display&prod_id=18485
>
> I know you are pressed for time and have put all the HARD parts off
> till the
> last minute but I think you will find a variable dimming system
> will make
> your night flying much more enjoyable.
>
> An appropriately rated rehostat will dissapate power (again a heat
> machine
> under your panel) and something like this may be what you want...
> http://www.aircraftspruce.com/catalog/elpages/rheostat.php
> put a on off switch ahead of this sucker so its not contantly making
> heat
> when you have the lights off.
>
> http://www.aircraftspruce.com/catalog/elpages/lc40.php
> This system looks nice due to its 4 channels of 1.5A each that can be
> tied
> together and controlled with one knob.
> I suggest keeping radios separate from flight instruments due to
> variations
> in overall brightness.
> http://www.aircraftspruce.com/catalog/elpages/k11aircraft.php
> This one has an adjustable master following system where you can have
> those
> bright systems lag behind say the less bright flight instruments.
>
> Hope some of this helps.
>
> Charles Reiche
>
> ---
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
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