Motor Bike Bulb Selection

I would try a higher quality bulb, or replace light fixture altogether, first...maybe go LED
http://www.jpcycles.com/product/310-069

http://www.littelfuse.com/tvs-diode.html
http://www.newark.com/thermistors

Answers like this remind me of Ann Landers. He (the OP) would like to know what is going on, not figure out what you would like for Christmas if you had a scooter.

Low battery electrolyte can cause a high or low voltage (but less likely current) condition. (Answered by Paulusgnome #4)

Switching to brights is probably energizing both elements, again a surge could be damaging them. Replacing the bulb is not really a longterm solution, although you should note that simply operating this light regularly will cause it to fail. It is not a particularly long life component. It's the vibration.

I believe voltage spikes are a likely culprit, although limiting to 12V is probably too low, I would shoot for 14V as a limit.

<...reluctant to opt for replacing the regulator section as it costs more...>

More than how many blown bulbs?

Option 3 would be more efficient.

hi thank you for your response,but i dont think that's the case in my bike as i had installed new batteries just 3-4 months ago

Have you measured the output voltage of the regulator (the voltage presented at the lamp's socket) yet?

There's no point second guessing a solution until you know what the problem is.

Myself I would use LED High/Low beam would use less power and more light.

Check if LED Head light has a build in regulater, Check at auto parts store.

The radically cheap engineering on these little bikes is amazing. We had a problem like this with moped headlights back in the eighties. Turns out that a burned out taillight was enough to allow the voltage to spike over 16 volts and give a nice, bright, but short-lived headlight. Peak system voltage should not exceed 14.2 volts. If you put on an extra load to regulate the voltage, be prepared to replace the alternator. These bikes are insanely cheaply built, but parts are very high.

What about a 15 volt 1 watt zener diode across the lamp to protect against spikes? and of course cathode to the + side of the circuit.

Bill

That'll work.

How about just finding out what is wrong and fixing it instead of engineering a patch?

What do you suggest? He has gotten a pretty good diagnosis, but often it's that one guy (Wal) who has the best idea. Or sometimes that one guy just sits on the sidelines and moans.

(That is what the OP asked)

What do you suggest?

I suggest that the OP reply to some of the questions that were tabled by some of the posters here.

I think the OP needs a starting point.

That is my best guess without knowing what model of Bajaj Pulsar it is. I found this info on Baja's electrical system with AC lighting. Some models have full DC electrical systems.

OP. What exact model of Bajaj Pulsar are you having lamp life problems with?

Hi guys i am sorry i was on a long vacation so couldn't reply to your message , i am using a bajaj pulsar 150cc DTSi 2006 model...

Have you looked at the link I provided?

yes,thank you. i have seen it. the circuit clearly indicates use of magnetics and regulator to generate 12V.but i couldn't find an details regarding the rating of the regulator i am using the part number to get some info, but no luck until now.i need to know the effect of using a 55/60W bulb instead of recommended 35/35W one on the AC Lighting circuit given in page 36 of the manual.

You will nearly double the current. Not advisable.

Have you performed any electrical measurements yet?

hi wal

i just came across another plan,the difference between 35W and 60W bulb will be their resistance right?(thereby drawing more current from the source) what if i could measure the difference and place a resistance in series with the 60W bulb ( of course there will be voltage drop across the resistor ,but as per my experiments low voltages 5-10 also works but with a glow dimmer than the one at 12V) will it work? or will the 60W bulb just lower its resitance further in case i add a series resistance thereby drawing more than the rated current from the regulator.please comment.

Take some measurements.

Hi wal,

i took some measurements,they are as below.

Battery-14.45(engine off)

-15.15 and rising (engine on)

the circuit schematics u had referred didnt exactly match the output of the regulator it had the following outputs and i measured the voltages on these pins

Blue/White(1)-4.76V

Blue/white(2)-4.85V

White-15.02 seems like the regulator is powered up by the battery which is not shown in the schematic page 33.

yellow- -0.02V

Red/Yellow- -0.02V

Black/yellow- ground (frame)

based on your reference ckt the input for the bulb will be through the yellow line but i couldn't see any voltage on that pin as shown above , i would have concluded that the regulator has gone bad,but the illumination lamps which are lit by the regulator( they are ON only when the engine is running) are working fine,i think the circuit might me a different one , please share your comments.

If that drawing is wrong then you should be looking for the right one.

Did you perform any AC measurements?

What is the voltage at the lamp holder, lights turned on and engine running?

The colours mean nothing to me here.

Did you perform any AC measurements?

• yes, i did please find the details below.
  

What is the voltage at the lamp holder, lights turned on and engine running?

• its in the range of 9.9-10.8 VAC .( i switched between high beam and low beam multiple times and have recorded the widest voltage range possible)
• is current measurement required?
  

• its 9.9-10.8 Vrms (as seen on a multimeter) so about 15.27 Vp if i am right.
  

its 9.9-10.8 Vrms (as seen on a multimeter) so about 15.27 Vp if i am right.

Were those measurements made only at idling speed or also with the engine revving faster?

Were those measurements made only at idling speed or also with the engine revving faster?

• these readings were taken at idling speeds
• when i increased the throttle , the voltage started dropping!!!!!
• it reached a low of 3.4Vrms.
• any idea whats happening?
• i think its this switching from high to low and again from low to high is causing the bulb to blow..what's your view....
  

Is a DC voltage also measured there when the engine revs?

yes, no change in the DC component it remained close to zero...

yes, no change in the DC component it remained close to zero...

If your instrument can measure frequency, make some frequency measurements at idle and revving to where you see the AC voltage dropping off.

It's late here now. I'm signing off till tomorrow.

Good night.

engine idling -13.084VAC - 120-130Hz (22-25% duty)

engine revving - 11.02VAC - 447 - 1kHz (34 - 4% duty)

by my understanding if i increase the speed of the motor the frequency should increase.

but here duty cycle is varying(decreasing)..

i used a different instrument (a reliable one) this time and the voltage readings seems to be different than the previous time the voltage didn't drop to very low voltages while the engine is revving...

Reliable instrument...?? What is it.? You probably want to recheck all your measurements now to establish reliable bench marks...

How are you determining the duty cycle?

Continuing now...

Compare the voltages measured at the lamp holder with those present at the alternator output (or regulator input). Are they the same?

the instrument itself gives the duty cycle..

yes the voltages at the lamp holder and the alternator are same....

In that case your regulator isn't doing a thing, ergo its busted.

Replace the regulator. Get a second hand one if a new one is too expensive.