Would a diode add to driving light longevity?

Hey you Electrical Engineers- can't I add a diode from radio shack to drop the voltage or regulate pulsing a little in my 2 (55watt) driving lights I added to my ride? The first one only lasted 15-20 hours.

i suspect the real culprit was the incesssant shaking...but a small drop in voltage may help!???

I know ohms law but you guys have thought this out better I'm sure.

what kind of bulbs?

sorry. They are 55watt, standard bulbs for driving lights. The replacement was identical to the original, except a contact was a spade rather than the bullet.

55 watts- divide by 12 = about 4.5 amps... Does that help?

I'm not an electrical engineer, but I did stay at a Holiday Inn Express last night.

Seriously though, I have dabbled in this stuff over the years, but if we have an electrical engineer in our midst, please confirm my findings.

You need an additional resistor in line to reduce the voltage to the light bulb, not a diode.

Using ohm's law, your light bulb resistance should be 2.6 ohms. An additional .25 ohm resistor should cut voltage to the bulb about 10%. But, I believe the resistor will need to handle more than 5.5 watts. (10% of the power).

Hope this help, Scooter Bob

Yeah, I thought a diode may be good because I don't know how pure the rectifier on board is doing. The resistor would help i'm sure, because most bulbs will last way longer with a significant drop in voltage...but it is a tradeoff. I just don't want to chage bulbs alot. It may even be cheeper to buy the whole kit on sale than buying bulbs!

A diode is simply a check valve for electrical current. It would not reduce the voltage nor would it stop an electrical pulsing.

Lights burn at a predetermined brightness so I'm not sure what kind of pulsing you are experiencing in your lights. Pulsing could be from using a circuit that does not have a large enough gauge wire in it. That would result in low amps being delivered to the lights. AND you could be seeing the first signs of regulator failure... (I'm opting for the light gauge wire in the circuit...)

Any diode able to handle this current (silicon rectifier) will cause a very small voltage drop of around .7 volts. Thats less than ONE volt. Also, unless it is way oversized, you may need a heat sink for it. Resistors can be sized to cause a more substantial drop, but then the resistor will need to be able to handle the power dissipation...meaning wasted energy,(heat), and mounting big ugly resistors ( or diodes on heat sinks) somewhere with air flow.

Neither component is really designed to do this job. Forget it.

There are electronic 'dimming' circuits that work on DC and will actually dim the output by reducing the input voltage. And lowering the voltage MAY increase the life of the bulbs, by reducing output...but wont help at all with the vibration. Either mount the lamps where they dont vibrate as much, or buy a different style that is vibration-resistant.

Having 'dimmed' (yellowish) driving lights seems counter-intuitive anyway. I'd rather be able to see further with them, and avoid things in the dark...like DEER! But you could simply replace the bulbs with 35W or 20W bulbs and accomplish the same thing.

I'd look into the pulsing. If it's noticeable while driving then you may have another issue. Stator, rectifier, regulator, battery, wiring? Typical voltage with motor running >3KRPM and not a lot of extra loads should be 13.8 - 14.2V or there abouts. My dash mounted gauge seems relatively accurate (with a significant dip when the brakes are applied, not sure the cause of this, thinking its the 2 stop bulbs and the antidive).

What does your dash voltage guage say? Is the pulsing noticable? Pulsing, if it exists, should be on all lights?

In my experience with less expensive aftermarket lights...($15-25 pair) verses the expesive stuff ($50-100) which I have yet to buy but always wanted to...

They usually have a very cheap bulb in the from the factory. I usually mount a pair of 55 watt driving lights under the back bumper of my truck that I can use to see where I am backing or connecting trailers and such. Just about always they first bulbs do not last that long. I put some on my tractor and the same thing happend...first bulb did not last long. Lot of virbration and bouncing around here...

I would try buying a good quality bulb for these lights to see if they hold up. That way you will have the extra light you wanted in the first place without all the extra components that could fail.

The pulsating you talked about kinda worries me some...may have recitfirer or something on the edge of going bad.

I turned mine on for the first time and the bulbs came on and one burned out within 10 seconds. I replaced it and have been running with the same bulbs for 5 years.

jonsmyth,

To be able to help could you provide the part number and manufacturer's name from the bulb?????

There is not obvoius pulsing. Just changes with the rpms- totally normal to drop brilliance with slow idle.

here is the bulb. (except without the blue coating)[ATTACH]38506[/ATTACH]

Sorry for the confusion.

Found some for $3 online on sale. I'll just change them out...

Try not to touch the glass with your fingers as it wil leave a film of oil on it and cause dark spots AND CAN ACTUALY BURN THE BULB OUT FASTER! As already stated, a diode will just drop around .7 - .8 volts depending upon the type. A 55 watt bulb will draw around 4.5 amps so the diode should be able to handlecloser to 10 amps for longevity. As far as any filtering, it won't do much for the rising and falling voltage. You could try a capacitor from hot to ground to filter out fluctuations of voltage.

I really don't know why you are having these problems though, I have a pair of cheap driving lights on mine and they work fine, and have never used any expensive ones, just cheap ones with no problems...

Maybe he's just a bike-o-chondriac.

From your statement shown at the bottom of this post, your concern is that when you rev the engine from idle, you see the bulbs increase in brightness. If this assumption is correct, then read on.

At idle your generator & rectifier combination is not putting out at their maximum potential.

As you increase the RPM's the generator armature spins faster inside of the field coil of the stator, thus generating more current. This increase in current causes the voltage level of the system to rise to a level where the regulator then clamps the rising voltage to prevent damage to components. This maximum voltage is in the range of 14.5 volts. At idle the generator & rectifier are lucky to be putting out enough to sustain the load on the battery. This increase in voltage, which is about 1 1/2 to 2 volts is about a 15% overall increase. As the system voltage increases, so does the current flow through the bulbs. This is enough to see the variation in output from the lights.

Looking at the chart below, which is cut out of the service manual, you will see that maximum output is around 4000 RPM's.

http://i1007.photobucket.com/albums/af193/gdingy101/rectifieroutput1986-1993-YamahaVent.jpg

There is not obvoius pulsing. Just changes with the rpms- totally normal to drop brilliance with slow idle.