Headlight Modulator, A Terrific Safety Device

headflash(gets your attention doesn't it?)

You may have seen reports indicating 78% of motorcycle accidents involve the driver of a car encroaching on the riders right of way. Statements to police usually go something like "I made the left turn and never saw the motorcycle" or "I pulled out from the side street and never saw him/her". Whether that 78% is truly accurate or not it's sure close enough. One accessory that can help prevent the "I didn't see the motorcycle" syndrome is a headlight modulator.

First off, modulators are legal for motorcycles in all 50 states. It's a federal law (CFR49). Click Here for the text of the law (you might want to print it and carry it with your registration just in case someone in law enforcement needs some educating). Your state may have its own law regarding use of modulators that you can check on your DMV website and print. It will not be in conflict with federal law.

About the modulators. There are several kinds but they all do the same thing. They 'modulate' (as opposed to flash) your headlight at a specific frequency of 240 cycles per minute or 4 cycles per second. Commercially made modules do 'not' turn the headlight bulb on and off which would give the filament a thermal shock with every cycle, they simply reduce the voltage so the life of your bulb is not affected (and may even be extended). All of the commercial units have a light sensor built into them because the federal standard forbids the flashing at night. At dusk the bulb will automatically stop modulating (unless you want it to, see the Signal Dynamics unit below)

So where do you get these things? You have choices ranging from simple plug and ride to a bit more involved wiring in your headlight bucket. There are major differences in flexibility as a result.

From the simplest to the most involved:

Kriss makes one of the simplest. In less than five minutes you can have your headlight ring off, headlight bulb unplugged, the Kriss modulator plugged into the back of the bulb, the wiring pressed into the modulator and the headlight re-assembled. This unit is loved by those who don't enjoy manhandling a soldering iron or just don't want to fool with the bikes wiring.

Downside? The unit will 'only' modulate the headlight when it is on high beam and you can not turn it off (unless you put a piece of tape over the light sensor) during group rides. The 'standard' unit will only handle a stock 80 watt bulb. If you have gone to a 100 watt Halogen bulb be sure to look at the heavy duty model.

Kissan makes another plug and ride unit. Pretty much the same as the Kriss unit it only modulates on high beam. There is a sensitivity adjustment provided so modulation of the headlight doesn't stop immediately if you ride through shade or a short tunnel. The Kissan unit will handle up to 115 watts, plenty for those who have upgraded to a 100 watt high beam bulb.

Signal Dynamics and Custom Dynamics used to supply the most flexible modulator they call Diamond Star. It had features missing in the other units like a 'heads up' mode that would modulate the headlight if you pressed the horn button even if the unit was turned off or it was night at the time. That latter part (modulating at night) was at odds with federal law and one of the manufacturers mentioned above reportedly ratted them out.

The Diamond Star unit now operates much as the Kissan and Kriss units do but requires more installation time. The upside it the Diamond Star costs about $30 less than the others. Very complete simple to understand instructions come with the unit but they also supply 3M clamshell connectors which should be thrown far, far away in favor of soldered connections. You can pick up the Diamond Star from Amazon.

The Diamond Star is supplied with a remote on/off switch. I mounted my switch in the left switch housing (this required about a 6" extension on the supplied wiring) box on the handlebar. 9-13-01accessoryswitch.jpg (42903 bytes) The photo doesn't show the actual switch supplied but it is installed in a hole drilled in the back portion of the switch box. Lots of room there for two switches and wiring actually.

But you don't want to pay something around $90 for the commercial units? You're pretty handy with a soldering iron and know your way around logic circuits? Not a problem, make your own! Click Here for a schematic and full explanation how you can build your own from scratch.

Which ever unit you choose the investment and effort is well worth it. You may never know how many times the modulator prevents someone from turning in front of you, perhaps saving your life in the process.

Oh, one thing you 'will' notice, other drivers tend to do one of two things when they see you coming in their mirrors. They either move out of your lane or they slow down. Don't be offended if some give you a single digit wave as you pass and they discover you 'wasn't a cop'.






Subpart B--Federal Motor Vehicle Safety Standards

Sec. 571.108 Standard No. 108; Lamps, reflective devices, and associated equipment.

S7.9.4 Motorcycle headlamp modulation system.
S7.9.4.1 A headlamp on a motorcycle may be wired to modulate either the upper beam or the lower beam from its maximum intensity to a lesser intensity, provided that:
    (a) The rate of modulation shall be 240 <plus-minus> 40 cycles per minute.
    (b) The headlamp shall be operated at maximum power for 50 to 70
percent of each cycle.
    (c) The lowest intensity at any test point shall be not less than 17
percent of the maximum intensity measured at the same point.
    (d) The modulator switch shall be wired in the power lead of the
beam filament being modulated and not in the ground side of the circuit.
    (e) Means shall be provided so that both the lower beam and upper
beam remain operable in the event of a modulator failure.
    (f) The system shall include a sensor mounted with the axis of its
sensing element perpendicular to a horizontal plane. Headlamp modulationshall cease whenever the level of light emitted by a tungsten filamentlight operating at 3000 deg. Kelvin is either less than 270 lux (25foot-candles) of direct light for upward pointing sensors or less than60 lux (5.6 foot-candles) of reflected light for downward pointingsensors. The light is measured by a silicon cell type light meter thatis located at the sensor and pointing in thesame direction as the sensor. A Kodak Gray Card (Kodak R-27) is placedat ground level to simulate the road surface in testing downwardpointing sensors.
    (g) When tested in accordance with the test profile shown in Figure9, the voltage drop across the modulator when the lamp is on at all testconditions for 12 volt systems and 6 volt systems shall not be greaterthan .45 volt. The modulator shall meet all the provisions of thestandard after completion of the test profile shown in Figure 9.
    (h) Means shall be provided so that both the lower and upper beamfunction at design voltage when the headlamp control switch is in eitherthe lower or upper beam position when the modulator is off.
    S7.9.4.2(a) Each motorcycle headlamp modulator not intended asoriginal equipment, or its container, shall be labeled with the maximumwattage, and the minimum wattage appropriate for its use. Additionally,each such modulator shall comply with S7.9.4.1 (a) through (g) whenconnected to a headlamp of the maximum rated power and a headlamp of theminimum rated power, and shall provide means so that the modulated beamfunctions at design voltage when the modulator is off.
    (b) Instructions, with a diagram, shall be provided for mounting thelight sensor including location on the motorcycle, distance above theroad surface, and orientation with respect to the light.

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