modulator

[KnightFox]

So, is this a problem witheselectronicounterfeits?

But I must admit, it can be very difficult to protecthem from direct lightning strikes.

An electro-mechanical siren would be far less prone to being taken out-of-service from a lightning strike.

Actually, Think of it this way:

A T-Bolt is standing in the middle of a field during a lightning storm. It happens to be so unlucky as to get hit by a lightning bolt. The surge of electricity has the potential to melt the insultation that surrounds the wires on the commutator on the chopper motor and would render it useless. Not only that, if the siren is not grounded properly, it can screwup the controller and possibly the radio reciever (if it is equipped with one)

If you ask me, all sirens are equally prone no matter what they are, electro-mecanical or electronic. The reason most townships go with electronic is because they are more energy effecient. Heck you can put one out in the middle of no where and charge the batteries off a set of solar panels.

[AllSafe]

One time I heard of a thunderbolt being struck by lightning and it sounded an alert until the power was shut off...the lightning strike fused the motor start relays.

[StonedChipmunk]

One time I heard of a thunderbolt being struck by lightning and it sounded an alert until the power was shut off...the lightning strike fused the motor start relays.

Haha, that would be awesome. Do you know how long it took them to shut the power off?

[jkvernon]

There was a recording of a system of single and dual toned Mods in Moore, OK a few years back in the siren contest. There's also a pretty good clip of one Moore's dual toned Mods in a tornado clip.

http://storms.newsok.com/cgi-bin/show_p ... rm_may2003#

It's under videos on the right side of the screen. It's the very last video titled May 9: Moore Tornado Developes.

[Robert Gift]

a lightning bolt. The surge of electricity has the potential to melt the insultation that surrounds the wires on the commutator on the chopper motor and would render it useless. Not only that, if the siren is not grounded properly, it can screwup the controller and possibly the radio reciever (if it is equipped with one)

If you ask me, all sirens are equally prone no matter what they are, electro-mecanical or electronic. The reason most townships go with electronic is because they are more energy effecient. Heck you can put one out in the middle of no where and charge the batteries off a set of solar panels.

Yes, I thoughthat was an excellent advantage, too.

The FS 2001 I recorded last week is entirely solor powered.
Didn't know that was possible.
Only two wires up it's pole were bare copper ground wires.

With a good lightninground, the electro-mechanical should be less
susceptible to lightning damage.

Wish our 2t22 could be battery powered.
I must dig 300' of trench to for a three-phase power line.
Lucky we happen to have three-phase that close.

[Whelen Rules]

But if a electromechanical siren is struck its out of the game, but an electronic siren might still have drivers left unharmed thus still allowing it to still sound if its in the middle of a tornado warning or other severe storms. Then after the storms they can replace the damaged drivers or the whole siren unit if its mechanical.

[Robert Gift]

Good point about some driversurviving.

But I would assume that a lightning bolt would take out an electronic siren
moreasily than mechanical.

Please correct me if I'm wrong. (Tied to the pole of a Modulator would be suitable punishment.)

Motors are less prone to damage, especially when well enclosed in metal
framework and shielding.
Electronicircuits are more sensitive to such voltage transients, even when the main amperage is conducted away by excellent grounding.

Would be interesting to read manufacturers'tatistics.

[KnightFox]

But Robert, Motors are as vunerable. I've seen a motor become a useless piece of metal after a surge of electricity hit it.

Also, the PCB of a Siren is most likely insulated from the actual metal casing.

[q2bman]

Motors can be burned to a crisp if struck directly by lightning in a way in which the current flows through the motor. Not likely since the relays are open. But, we're talking millions of volts of electricity. If directly struck and the current flows through the equipment, anything will be destroyed. But, that's why the control boxes have lightning supressors.

Electronics are prone to damage just from near strikes and magnetic fields. They would not need to be directly struck for damage to occur. Even though steps have been taken to lessen the risk I.E. Shielding, Grounding, Surge Supression. They still would be more fragile I would think.

[Whelen Rules]

Q. Are Whelen electronic sirens more susceptible to lightning than our competitor's mechanical sirens?

A. No. Any siren sitting on a pole in the middle of an open area is susceptible to lightning. The key is how well the siren is protected from the inevitable strike.

Q. How will lightning damage a siren?

A. There are two basic ways that lightning can damage a siren. One way is from energy that is picked up through the atmosphere by a nearby strike. This energy is often coupled through the radio antenna or radio coax cable. The other way is from energy that is coupled onto the AC power lines, in the form of a voltage transient. In either case, the siren must be protected from the inevitable.

Q. How does Whelen protect its sirens from lightning strikes?

A. Whelen does a number of things to protect against lightning damage.

1. Clearly, proper grounding is essential in protecting the siren. We recommend a minimum of two separate 4 AWG copper ground wires, one from the electronics cabinet and one for the steel pole top mounting bracket and pole mounted radio antenna. The copper wires act as low resistance paths, which help divert lightning energy away from the siren, to ground. The ground path from the pole top mounting bracket makes a nice lightning rod.

2. All Whelen sirens include a Lightning Arrestor for the AC line voltage. This is a gas discharge type of device that provides a low resistance path, to ground, for high voltage transients.

3. The battery charger, on all Whelen sirens, is equipped with a line filter and transient protection circuit that exceeds IEC801 requirements. All Whelen battery chargers are UL listed.

4. A gas discharge type of device is included in every Whelen siren to protect the electronics, in particular the radio, from transients entering via the radio antenna path. This device is often referred to as a "polyphaser".

5. Whelen recommends rigid steel conduit to enclose the wiring from the cabinet to the speaker array or rotor mechanism. This reduces atmospheric coupling of lightning energy into the wires, and therefore, into the electronics cabinet.

Q. Will lightning damage Whelen's non-metallic speakers more than a conductive, metal speaker?

A. No. Whelen's omni speakers are made of fiberglass reinforced Lexan? and Whelen's directional speakers are fiberglass. In either case this is a non- conductive material. Lightning will seek the path of least resistance, which is the steel pole mounting bracket and its associated ground wire. The pole top mounting bracket is a nice lightning rod.