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Electronica (Headlight modulators)

By Sam

I've made it a fair way into the construction and design of a headlight modulator for my scooter. What is a headlight modulator you ask? It is a device that causes the headlight of the scooter to pulse on and off at about 240 beats per minute. It contributes to motorcycle safety by making the vehicle far more visible.

Some design aspects, mandated by federal law, are that the light not flash between full brightness and being completely off. Instead, it must go between full brightness, and no less than about half brightness. That is the difference between 'flashing' and 'modulating'. The rate that the light modulates is also mandated by law, to be between 200 and 280 beats per minute. This keeps it from causing 'target fixation' that some strobes cause in drivers, as well as distinguishing it from emergency vehicle strobes.

Another design parameter is that it must turn itself off at night, returning the light to normal operation.

The one I'm working on now uses a pair of 555 timers to modulate. One creates a 300Hz flicker at about 50% duty cycle, producing an output that looks half as bright as normal (you don't notice the flicker, because 300Hz is fast enough to cause persistence of vision to make it look like a continuous brightness). The other timer flickers at the 240 beats per minute, also at a 50% duty cycle, switching between the dimmed output, and normal output.

A relay connected to a small circuit with a phototransistor checks ambient light level. When it moves above a preset level, the phototransistor activates the relay, which switches the headlight to modulated mode. When it goes dark, the relay snaps back to its closed position, which allows the headlight to work as normal. This is designed to cause the 'default' status, in case of malfunction, to be normal operation, another aspect required by law. If the circuit fails, the light must return to normal operation.

Currently the entire mess is sitting on the dining room table, a nest of wires attached to a prototype board. I'm using an old AT computer power supply to provide the 12V to the board. I purchased a set of organizer trays to hold my electronics stuff, and that has helped organization a lot, but it is still a bit of a mess. I don't think it is possible to work on electronics without making a mess.

Anyway, I've got this, as well as a few other interesting projects, moving forward to increase the safety of my scooter. Recent studies have confirmed what many suspected, that motorists simply don't see motorcycles. A combination of smaller form factor, as well as a level of 'unexpectedness' prevents people from noticing motorcycles. Most motorcycle accidents are caused by a cage driver (thats what we call you car-bound people) not seeing a motorcyclist, and running into them, usually by making a left turn into them. All the studies have recommended that motorcyclists do anything in their power to make themselves more visible.

In the 70's, federal law mandated that motorcycles leave their lights on all the time. Since then, all motorcycles have been made without the ability to turn the lights off. My scooter has a light switch, but it only lets you choose between high beam and low beam. That helped visibility, but with the advent of daytime running lights on cars, motorcycles are losing their edge again. Headlight modulators are one thing that makes the motorcycle much more visible.

Some people find them annoying, but because mine will still be controlled by a manual switch, there are things that can be done to make them less annoying. For instance, it can be turned off while at a red light, so the driver ahead of you isn't forced to stare at it in the rear view mirror. However, one thing must be made clear. Headlight modulators are despised by some, misunderstood by many, but seen by all. And that is the important thing.

Stay tuned for more info on the circuit, including diagrams, once I have it tuned up the way I want it. Also, I've got a neat circuit in the works for the brake lights too, I'll post more about that once I get started on it. There are also plans in motion to add auxiliary brake and turn signal lights (all LED of course), add strategic and attractive 3M reflective material and increase horn volume. My hope is that once I'm done, no one will be able to ignore the flashing, brightly colored streak of light and sound that my scooter will become.

By Sam

My name is Sam. I live in St. Louis, MO, USA. I'm moderately skilled in web design. I drive a performance motorscooter. I'm not a compu-zealot. I use a Mac, a PC, and a Linux box, all of which are highly modified or home built. I don't smoke. I have part of a degree in Physics. I consider myself a Buddhist. I'm a vegetarian. I'm a conscientious objector. I dig many musical styles. Yeah.


Well Sam, interesting project you are working on. I'm not sure how old this article is but if you have finished a working model I'd like to see it. We have a couple things in common . I ride a Yamaha Majesty scooter, 400cc just about daily back and forth to work. I also enjoy tinkering w/ all make of computers, macs are still my favorite though, and enjoy just about all styles of music. However I'm a devout Roman Catholic, libertarian leaning conservative meat eating Army vet. We live in Indy In. Love meeting people of differents views especially scooter riders. Take care and God bless - Erwin

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