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Ignition Battery Switch

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Old 01-24-2008, 06:59 PM
  #1
dasintex
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Default Ignition Battery Switch

I am building a GS P-51; I will be using the 'Power Expander Sport Plus' with two 6 Volt NiMh packs for Reciever/Smart Fly Panel; I will have 2 manual switches, one for each battery in a fuselage compartment, so I can actually cut off the battereies to the Reciever/Smart Fly Panel; I will also be using the Pin/Flag Fail safe switch. The problem is the Ignition battery, which will be a single 4.8 NiMh pack located in the engine compartment; I would love to be able to install a 3rd switch in the Fuselage Compartment, to be able to cut off the battery to the Ignition Module; however, I don't want to run a chance of any radio interference by having the wires running from the engine compartment to this switch; is a manual cut off switch for the Ignition battery nessesary, I am trying to eliminate any unsightly switches on the surface and I don't want to have to build another compartment, I plan on installing a small charge port up front to be able to charge the ignition battery without having to remove the cowl; if an actual mechanical Ignition ON/OFF switch is recomended; can another Smart Fly Pin/Flag switch be some how modified to be used as an ON/OFF switch; as it is extremely unobtrusive.

Thanks, Doug.
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Old 01-24-2008, 07:32 PM
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Default RE: Ignition Battery Switch

Well you could use a smartfly optical cut off on the ignition that way you won't need a mechanical switch.
But you will have to have a charge port.
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Old 01-24-2008, 07:52 PM
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Default RE: Ignition Battery Switch

Not sure what you mean; I will be using the Smart Fly Optical Ignition Cut Off, it comes with this Smart Fly Power Expander; the Smart Fly Ignition Cut Off Receiver normally goes between the the Engine Ignition Module and a Mechanical Ignition ON/OFF Switch; I am just trying to eliminate this Mechanical Switch.
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Old 01-25-2008, 08:56 AM
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Default RE: Ignition Battery Switch

Hi Doug,
I do not use a switch on my ignitions any more. I just use the Cutoff receiver module as the switch. The module will draw a few milliamps a day from the battery in the off position. I disconnect mine when I am home to charge anyway. I don't think you would have a problem unless you left it for a long time without disconnecting or charging.
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Old 01-25-2008, 09:26 AM
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Default RE: Ignition Battery Switch

The problem is that this is a warbird and the ignition battery will be in the Engine Compartement closed in by the Cowl; to disconnect the Battery would be a pain because you would have to remove the Cowl to do so, and I would like to avoid placing a switch on the surface, however; your Pin/Flag switch is so unobtrusive; leaves a small footprint on the surface, no more than an earphone jack, is there a way to modify it to work like a ON/OFF switch by inserting the pin.

Doug.
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Old 01-25-2008, 09:41 AM
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Default RE: Ignition Battery Switch

Hi Doug,
Sorry, the contacts in the Pin & Flag failsafe switch can only handle about 50 milliamps, no where near what you need for an ignition. If you really need a switch I would mount one inside as far forward as you can get and away from the receiver wiring but still accessible. I would not worry about ignition noise as long as you don't have the ignition wires and receiver wires on top of each other.
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Old 01-25-2008, 10:15 AM
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Default RE: Ignition Battery Switch

Fromoco's "Badger" pin type failsafe switch is rated at 15 amps
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Old 01-25-2008, 10:20 AM
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Default RE: Ignition Battery Switch

Hi Larry,
That is true but it is also the size of a JR heavy-duty switch which I think Doug was trying to avoid. The Badger switch uses the pin switch to turn on/off some FET transistors that actually pass the current. The pin switch does not pass any current itself.
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Old 01-25-2008, 10:30 AM
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Default RE: Ignition Battery Switch


Quote:
ORIGINAL: rrritchey

Hi Larry,
That is true but it is also the size of a JR heavy-duty switch which I think Doug was trying to avoid. The Badger switch uses the pin switch to turn on/off some FET transistors that actually pass the current. The pin switch does not pass any current itself.
Oh, I was not aware of any other pin switches & don't know what FET transistors are []
Sorry I will be ritiring to my room to get my foot out of my mouth
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Old 01-25-2008, 10:40 AM
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Default RE: Ignition Battery Switch

Hi Larry,
Don't worry about it. I was just trying to explain why the Badger can handle 15 amps but my pin cannot. A FET transistor is a "Field Effect Transistor" (redundant, huh). They have a very low resistance when turned on and are excellent for use as switches of high currents.
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Old 01-25-2008, 11:58 AM
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Default RE: Ignition Battery Switch

Robert;

Appreciate the info; I think what I will do is put a small charge port on the surface somewhere up front, and mount a switch on the inside of fuselage, as far up front as you suggested; so when I take the wing off, I can turn the ignition battery off then, and if I need to do a field charge I can charge through the port, I will get a battery pack with 2 leads, one for the switch and the other for the charge port, any problem doing a field charge this way and having the battery still connected to the Smart Fly Ignition Receiver because the switch would be on until I remove the wing?
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Old 01-25-2008, 12:34 PM
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Default RE: Ignition Battery Switch

Hi Doug,
That should work just fine.
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