Probably the reason that moving boats get hit MUCH less often than anchored boats. Same reason applies to electro chemistry as the transfer rate exponentially increase for a 'moving fluid' than a non moving electrolytic fluid.
Lightning + Mast = ????
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Transorb or TVS (transient voltage suppression).. This or the equivalent surface mount part would be typical for LNB's used in consumer satellite
This particular one is 15 volts but they come in all voltage and power ratings (LNB would use about a 30 volt part)
http://www.digikey.com/product-detail/en/3KP15A/3KP15ACT-ND/2699677
This particular one is 15 volts but they come in all voltage and power ratings (LNB would use about a 30 volt part)
http://www.digikey.com/product-detail/en/3KP15A/3KP15ACT-ND/2699677
Been struck twice at the flight levels, both times from the rear between cells in clear air and leaving a contrail. Hundreds of pinhole exits....mostly around rivets. One strike burned right through the glass Nav lense completely vaporizing the six screws that held it on. Inside the plane became a fluorescent tube according to the passengers. Biggest expense was avionics and damaged wiring for the capacitive fuel indication system........imagine that, arcs in the fuel tanks. My guess is most jets in their lifetime will be struck at some time or other.
A direct hit is going to cause damage period. Obviously mitigating that damage and or injury is the goal. Avoidance is probably your best bet. We have been playing with an ADS-B receiver linked to an IPad via wifi( need something to keep us busy) About $700. Works great. Provides Nav position to 1 or 2 meters, but more importantly, free weather data including composite radar( not real time though). I have not used it on the boat yet, and understand being ground based it may have limits beyond the horizon.( Nav data is GPS with ground based WAAS) If they make it satellite based, and allow a marine version, it could have a use on the water for collision avoidance also.
transient absorbers
NMEA sends data at 4.8k bps and SeaTalk at 18k bps if memory serves.
These are standard 5 volt signals so the voltage swing is a "square" wave on of 5 volts and off of 0 volts. You could make the observation that 4.8 k bps is a 4.8 kHz signal. Now as we all remember from our electrical engineering classes in high school ;-) there is not much of a current in signal wires, hence their small diameter, so there would not be a lot of magnetic field produced to clamp them. Conversely it does not take much magnetic filed to clamp them either!! So you would need a lot of turns on your choke (that's what transorbers used to be called when I went to school).
If you are trying to keep lightning voltages out of the equipment then the transorber would need to be low impedance (impedance in AC circuits is the same thing as resistance in DC currents) to the signal and high impedance to the lightning spike not a high impedance to the signal as RichH posted (sorry Rich it was probably a typeo).
Given that 4.8 kHz to 18 kHz is right in the frequency of lightning strikes it would seem to be pretty hard to build a device that could distinguish between them. I'm thinking that you would want to avoid the whole issue by keeping the lightning out at a place upstream from the device (way upstream) because even if you could build one the very high voltages in a lightning strike would just build up on one side and jump around the device (since it can't pass through it) via the air.
I'd be thinking of some sort of coil surrounding the mast base wires tied into the common ground circuit. The problem is the dedicated signal grounds from the wind sensors and the radio antenna coax ground as you can't really tap in to those ground circuits without effecting the performance of them or the other circuits (noise, turn on/off transits, RF into the DC power, etc)
That drives me to think the only way to protect the equipment is to disconnect it at the mast base and plug the up mast cables into a ground receptical and provide a low impedance path to the water surface that does not go through the cabin.
For the record Raymarine requires a ferrite bead on all seatalk cabling as close to the display head as possible. Presumably to keep RF out.
Perhaps we are approaching the problem from the wrong angle. Why don't we just get congress to pass a law outlawing lightning strikes? In fact, while they are at it, lets get them to repeal all the laws of physics as those things are always getting in the way of having fun.
NMEA sends data at 4.8k bps and SeaTalk at 18k bps if memory serves.
These are standard 5 volt signals so the voltage swing is a "square" wave on of 5 volts and off of 0 volts. You could make the observation that 4.8 k bps is a 4.8 kHz signal. Now as we all remember from our electrical engineering classes in high school ;-) there is not much of a current in signal wires, hence their small diameter, so there would not be a lot of magnetic field produced to clamp them. Conversely it does not take much magnetic filed to clamp them either!! So you would need a lot of turns on your choke (that's what transorbers used to be called when I went to school).
If you are trying to keep lightning voltages out of the equipment then the transorber would need to be low impedance (impedance in AC circuits is the same thing as resistance in DC currents) to the signal and high impedance to the lightning spike not a high impedance to the signal as RichH posted (sorry Rich it was probably a typeo).
Given that 4.8 kHz to 18 kHz is right in the frequency of lightning strikes it would seem to be pretty hard to build a device that could distinguish between them. I'm thinking that you would want to avoid the whole issue by keeping the lightning out at a place upstream from the device (way upstream) because even if you could build one the very high voltages in a lightning strike would just build up on one side and jump around the device (since it can't pass through it) via the air.
I'd be thinking of some sort of coil surrounding the mast base wires tied into the common ground circuit. The problem is the dedicated signal grounds from the wind sensors and the radio antenna coax ground as you can't really tap in to those ground circuits without effecting the performance of them or the other circuits (noise, turn on/off transits, RF into the DC power, etc)
That drives me to think the only way to protect the equipment is to disconnect it at the mast base and plug the up mast cables into a ground receptical and provide a low impedance path to the water surface that does not go through the cabin.
For the record Raymarine requires a ferrite bead on all seatalk cabling as close to the display head as possible. Presumably to keep RF out.
Perhaps we are approaching the problem from the wrong angle. Why don't we just get congress to pass a law outlawing lightning strikes? In fact, while they are at it, lets get them to repeal all the laws of physics as those things are always getting in the way of having fun.
hey Walt
are you seriously suggesting a 30 volt TVS is going to do anything in a lightning strike????, in a microwave surface mount situation????
I believe we should be looking at those "lightning arrestor" that are common on coax antenna cables. A "tee" that connects the coax outer sheath to ground (outside the building please)
are you seriously suggesting a 30 volt TVS is going to do anything in a lightning strike????, in a microwave surface mount situation????
I believe we should be looking at those "lightning arrestor" that are common on coax antenna cables. A "tee" that connects the coax outer sheath to ground (outside the building please)
hey flynfol
A great insight, airplanes are always "in windy conditions" so wind is not the end all solution.
I find it interesting that you where "leaving contrails". Kinda like those lightning researchers that send a rocket with thin wire into the lightning cloud to force a strike????
There is so much stuff here that we don't know!!!!!
How does wind effect the dynamics?
What effect does the boat moving through the water and disturbing the electrical charge induced on the surface have?
Can pigs really fly?
will congress ever get us a budget?
who is really buried in Grants tomb?
A great insight, airplanes are always "in windy conditions" so wind is not the end all solution.
I find it interesting that you where "leaving contrails". Kinda like those lightning researchers that send a rocket with thin wire into the lightning cloud to force a strike????
There is so much stuff here that we don't know!!!!!
How does wind effect the dynamics?
What effect does the boat moving through the water and disturbing the electrical charge induced on the surface have?
Can pigs really fly?
will congress ever get us a budget?
who is really buried in Grants tomb?
These are 3KW transorbs - come in all sort of voltage ratings. The lower the voltage, the higher the current.
They absolutely do lower the field return rate for electronics due to lightning damage. But of course they would get vaporized along with everything else if the entire energy of strike was input to the device.
The transorbs or TVS that I had the link for are semiconductor devices. If the voltage is lower than the transorb, they are very high impedance for all frequency. They only become a very low impedance if the voltage on the line they are protecting gets up to the TVS turn on voltage.
As an example for the NMEA application, you would simple connect one side of the TVS to the signal line and the other side of the TVS to ground. You would do this very close to the input of the instrument you are protecting. You of course cant connect a TVS directly on an RF cable as it would completely screw up the RF impedance/transmission.
In an lightning strike, there is a lot of current going from the sky to ground and no matter what you do on the boat (with ferrites or??), that current is going to create a magnetic field which will couple with all other conductors. This could be a circuit trace inside an instrument or a DC power run or the NMEA serial data com line. There is really no way to stop these conductors from having current generated on them because of the strike. But if you have a TVS on the signal line to ground close to the input, at least the transient signal is dissipated in the TVS before it enters the electronics. If the electro or magnetic coupling occurs on the circuit board traces inside the device, not much you can do except to try and shield the device from both the eclectic and magnetic field (ie, put it in a steel microwave oven for example)
They absolutely do lower the field return rate for electronics due to lightning damage. But of course they would get vaporized along with everything else if the entire energy of strike was input to the device.
The transorbs or TVS that I had the link for are semiconductor devices. If the voltage is lower than the transorb, they are very high impedance for all frequency. They only become a very low impedance if the voltage on the line they are protecting gets up to the TVS turn on voltage.
As an example for the NMEA application, you would simple connect one side of the TVS to the signal line and the other side of the TVS to ground. You would do this very close to the input of the instrument you are protecting. You of course cant connect a TVS directly on an RF cable as it would completely screw up the RF impedance/transmission.
In an lightning strike, there is a lot of current going from the sky to ground and no matter what you do on the boat (with ferrites or??), that current is going to create a magnetic field which will couple with all other conductors. This could be a circuit trace inside an instrument or a DC power run or the NMEA serial data com line. There is really no way to stop these conductors from having current generated on them because of the strike. But if you have a TVS on the signal line to ground close to the input, at least the transient signal is dissipated in the TVS before it enters the electronics. If the electro or magnetic coupling occurs on the circuit board traces inside the device, not much you can do except to try and shield the device from both the eclectic and magnetic field (ie, put it in a steel microwave oven for example)
Walt
I guess I don't understand what these thing do. Do the open to ground on a high enough voltage? Like the overpressure valve on a hot water heater opens when the pressure gets to high?
I guess I don't understand what these thing do. Do the open to ground on a high enough voltage? Like the overpressure valve on a hot water heater opens when the pressure gets to high?
I am supposed to be working today so that I can go to Lake Havasu early. On the other hand, when I’m at work, I screw around on the internet too much so I guess technically Im still working.
Here is a diagram of how you might place a TVS on the NMEA signal lines. As always, these do not prevent damage in all cases. But if you made 1000 instruments with these transorbs and the same amout without and checked after 5 years, you would have less of these damaged if they had the TVS.
Here is a diagram of how you might place a TVS on the NMEA signal lines. As always, these do not prevent damage in all cases. But if you made 1000 instruments with these transorbs and the same amout without and checked after 5 years, you would have less of these damaged if they had the TVS.
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