The evolution of vehicle warning lights
LED, Strobe or Halogen? To start with only Halogen lamps were available for any form of warning lighting. These were originally sealed beam units that were big, and later as technology developed, along came the halogen lamp.
Here we take a look at the differences in technology and the benefits of each design.
The Halogen Rotator Lightbar
The first designs used a rotator mechanism or beacon to distribute light output so that it could be seen through 360 degrees. These rotators were supplemented with mirror assemblies to create the effect of more lights in the unit.
The specifications of light output from these light bars is still used today in terms that the light must be able to be seen through 360 degrees. Some of these lightbars had 2, 4, 6 and even more rotators. This gave a brilliant light output, but the problem was the current draw from the battery. With each rotator taking 4.6 amps each, you can see that a massive amount of current was required to run these lights.
Emergency vehicles in particular the police, who often had lights running for hours while attending to an incident, would return to a flat battery in their vehicle. To combat this, “Fast Idle” circuits were developed so the car could be left locked with the engine running, so the battery didn’t go flat. Even with today’s technology, the rotator lightbar makes an excellent warning light system, but current draw and replacement parts have to be born in mind.
The Strobe Lightbar
During the 1990’s companies began experimenting with strobe lighting technology. The strobe lightbar was the next generation of warning light, and consisted of a number of strobe lamps and an electronic circuit to drive the individual light units.
The lights inside the lightbar were of two types. There was the linear strobe light head, and the directional halogen light unit. These combined to give a powerful 360 degree light output, which was particuly good in poor weather conditions.
The strobe lightbar emerged in many designs mostly from the same companies who were producing the rotator lightbars. Although the strobe lightbar still used halogen directional lights, they drew less current (depending on configuration) than the rotator lightbar.
Of the many companies producing these strobe lightbars, the Whelen Engineering Co from Chester Connecticut in the USA made one of the most powerful and best looking lightbars ever made. This was known as the “Edge 9000 Series” Lightbar, and went on to become the industry standard for strobe lightbars. The picture above left shows a Whelen Edge 9M Strobe Lightbar.
The LED Lightbar
There are more designs of LED Lightbars on the market today than you can shake a stick at. They are all trying to do the same thing, and that is to emulate the light output of the humble rotator lightbar.
LED’s first started to appear on the emergency vehicle lighting market in the mid to late 1990’s. At that time the only LED’s available were what are now known as Generation 1 LED’s. These were simply 5mm diodes arranged into a cluster to form a light head. Several light heads were added in to the frame/housing to make the lightbar.
The companies making the older strobe and rotator lightbars saw this as a natural step forward, and began manufacturing LED Lightbars. To start with, some of these lightbars did not give particuly good 360 degree light output. The reason for this is that LED’s are highly directional, and generally have a good output to the front, but poor when viewed from the side or off-axis This meant that lots of these lightbars had bright light output to the front/rear and side, but little or no light visible from the corner (intersection) area. As time went on these lightbars began to use optical enhancement of the light beam for improved off-axis light output. Generation 2 LED’s then emerged which gave better off-axis viewing, but it wasn’t until what is know as “Generation 3” LED’s became available that things really moved on.
Basically there are two types of light head used to make today’s lightbars. These are the “TIR” light head which have internal optics to concentrate the light beam, and then on top of that a diffuser lens to widen the spread of light. The second type which is now becoming the standard fitting in most lightbars is the “Linear LED Light Head”.This type of light has a number of LED’s mounted in a linear lens. Some companies use a reflector mounting to achieve the same effect. This effect is a much brighter, much wider angle light output. There are new designs using increasingly cleaver optics coming onto the market every few months.
The main advantage of LED Lighting over the strobe or rotator models is the difference in power requirements that they need to function. Today’s fully loaded LED Lightbar needs a fraction of the power of the old rotator design.
LED Lighting can be left on for long periods of time without flattening the vehicles battery. Because of the size of the light modules, designs can be made to be low profile thus saving fuel whilst the vehicle is in motion, as well as low power consumption.
Finally, due to the nature of the LED diode there are no filaments to burn out, or bulbs to break. Essentially they are maintenance free. Yes these products have a high capital purchase price when compared to a rotator lightbar. but over the years with nothing to maintain, fuel savings because of low profile design and up to 100,000 hours of operation, the LED Lightbar will pay for itself over time.
