I have the A600 combination wing-tip light system installed in my RV-6. It's powered thru the control-vision exp-2V electrical bus system. The exp system uses self-resetting "poly-fuses" for circuit protection. Unfortunately, the poly-fuse for the NAV light circuit is set at 7 amps and the system draws approx. 7.2 -7.3 amps with the alternator on and ussually trips after being on a few minutes. I'm wondering if there is an easy and inexpensive fix. Perhaps installing different bulbs or maybe putting a resistor in line. I only need to reduce the draw slightly to resolve the problem. Has anyone seen this problem before? Any ideas?.......jacksel
Van's Air Force
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NAV light current draw
- Thread starter jacksel
- Start date
rzbill
Well Known Member
Add a fuse?
I have not yet had personal experience with poly fuses, but I do remember reading that one can parallel polyfuses to gain current capacity, and not necesarily the the same size is required. If that is true, you can consider modifing your buss by purchasing another polyfuse and soldering it into place on the leads of the fuse that is failing.
Sorry, but my weak memory prevents me posting where I read this about the PTC thermistor "polyfuses". I do know it is on one of the "common" experimental aircraft electronics related sites.
I have not yet had personal experience with poly fuses, but I do remember reading that one can parallel polyfuses to gain current capacity, and not necesarily the the same size is required. If that is true, you can consider modifing your buss by purchasing another polyfuse and soldering it into place on the leads of the fuse that is failing.
Sorry, but my weak memory prevents me posting where I read this about the PTC thermistor "polyfuses". I do know it is on one of the "common" experimental aircraft electronics related sites.
Self-resetting circuit protection...
I do not know if this applies to the "poly-fuse" that you are talking about, but let me share a recent experience with "self-resetting" circuit protection that has me pretty leery about it.
We fitted our Fire Trucks in Nassau Bay with piezo-electric ice-chest coolers to keep bottled water cold. These were wired in to the charging circuits that keep the truck batteries topped off. A couple of weeks ago, one of the coolers was removed to be worked on, and the plug was left dangling up in the open "basket" area of the truck. Well, we went on a fire call in the rain, and when we came back, one of the firefighters asked "Do you smell smoke?" I looked back and there was a big black column of smoke rising out of our truck!
I yelled for a CO2 extinguisher and climbed up top, where I saw a nice orange glow. It turned out that the "hot" end of the plug had shorted in the rain, igniting the rubber cord, as well as some wood blocking that was next to it. It was quickly extinguished, but a minute later, it started glowing again! I hit it once more, it went back out, and I yelled for someone to disconnect the power! It did this a couple more times before they got the power cut.
What had happened? Well, when we added this cooler circuit, someone wired it to a self-resetting breaker. The circuit shorted, the thermal breaker eventually tripped, and the problem was solved - until the breaker cooled down and reset. Of course, since the short was still present, the process kept repeating! The breaker did a good job of protecting the upstream power supply, but in doing so, it was bound and determined to let the downstream device destroy itself - and the whole vehicle, if we hadn't been there!
Just thought this might get people thinking...
Paul
I do not know if this applies to the "poly-fuse" that you are talking about, but let me share a recent experience with "self-resetting" circuit protection that has me pretty leery about it.
We fitted our Fire Trucks in Nassau Bay with piezo-electric ice-chest coolers to keep bottled water cold. These were wired in to the charging circuits that keep the truck batteries topped off. A couple of weeks ago, one of the coolers was removed to be worked on, and the plug was left dangling up in the open "basket" area of the truck. Well, we went on a fire call in the rain, and when we came back, one of the firefighters asked "Do you smell smoke?" I looked back and there was a big black column of smoke rising out of our truck!
I yelled for a CO2 extinguisher and climbed up top, where I saw a nice orange glow. It turned out that the "hot" end of the plug had shorted in the rain, igniting the rubber cord, as well as some wood blocking that was next to it. It was quickly extinguished, but a minute later, it started glowing again! I hit it once more, it went back out, and I yelled for someone to disconnect the power! It did this a couple more times before they got the power cut.
What had happened? Well, when we added this cooler circuit, someone wired it to a self-resetting breaker. The circuit shorted, the thermal breaker eventually tripped, and the problem was solved - until the breaker cooled down and reset. Of course, since the short was still present, the process kept repeating! The breaker did a good job of protecting the upstream power supply, but in doing so, it was bound and determined to let the downstream device destroy itself - and the whole vehicle, if we hadn't been there!
Just thought this might get people thinking...
Paul
I have the exp-2 bus on my RV-4. When I was checking the current draw, I noted that I would have had the same problem. My set-up allowed me to switch the power source wires to the 11 amp out put since these were spare to my set-up. I have the aero-flash strobe-nav light system and that draws more than the 7a.
Good luck
Bill Glasser
RV-4 flying in Phase I
Good luck
Bill Glasser
RV-4 flying in Phase I
gmcjetpilot
Well Known Member
Amps
Nav about 2 amps per wing, 1 amp tail (of you have the wing tip white nav assume 1 amp each)
Strobes vary but about 3 amps a wing, 2 amps tail.
That should cover you for planning purposes.
If you add it all up it is about 13 amps. Some single flash strobes are a little less. LED NAVs are much less than the ones listed above. Ball park though is 11-13 amps. Don't forget 4 amps per landing light, or 8 amps. So we are up to 20 amps plus with an amp or two for the cockpit.
Nav about 2 amps per wing, 1 amp tail (of you have the wing tip white nav assume 1 amp each)
Strobes vary but about 3 amps a wing, 2 amps tail.
That should cover you for planning purposes.
If you add it all up it is about 13 amps. Some single flash strobes are a little less. LED NAVs are much less than the ones listed above. Ball park though is 11-13 amps. Don't forget 4 amps per landing light, or 8 amps. So we are up to 20 amps plus with an amp or two for the cockpit.
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vlittle
Well Known Member
Poly fuses
One of the characteristics of incandescent lights, such as Nav (aka Position) lights is that they have a very low resistance when cold (turned off).
When you switch the power on, they draw a much larger current than the steady state current that you can measure.
This has the effect of heating up the Poly Fuse to above its 'trip' point. The steady state current, if it's above the 'hold' point will not allow the Poly Fuse to reset.
Therefore, follow the advice to use a larger Poly Fuse, or solder another one in parallel with the existing one, or use a 'ballast' NTC thermistor...
What's an NTC?.. it's a negative temperature coefficient thermistor. They are used in the EXP Bus for the landing/taxi light circuits, but not the other circuits. They have a high resistance when cold, and a low resistance when hot (kind of like the opposite of a Poly Fuse).
They help to limit the inrush (cold) current, preventing false trips of Poly Fuses, regular fuses or breakers AND they increase the life of your lights by minimizing thermal shock.
FMI, go to Digikey.com and search for CL-21. These are what I use for landing lights. Smaller ratings would be appropriate for Nav lights.
Vern Little
-9A
One of the characteristics of incandescent lights, such as Nav (aka Position) lights is that they have a very low resistance when cold (turned off).
When you switch the power on, they draw a much larger current than the steady state current that you can measure.
This has the effect of heating up the Poly Fuse to above its 'trip' point. The steady state current, if it's above the 'hold' point will not allow the Poly Fuse to reset.
Therefore, follow the advice to use a larger Poly Fuse, or solder another one in parallel with the existing one, or use a 'ballast' NTC thermistor...
What's an NTC?.. it's a negative temperature coefficient thermistor. They are used in the EXP Bus for the landing/taxi light circuits, but not the other circuits. They have a high resistance when cold, and a low resistance when hot (kind of like the opposite of a Poly Fuse).
They help to limit the inrush (cold) current, preventing false trips of Poly Fuses, regular fuses or breakers AND they increase the life of your lights by minimizing thermal shock.
FMI, go to Digikey.com and search for CL-21. These are what I use for landing lights. Smaller ratings would be appropriate for Nav lights.
Vern Little
-9A
