Lights that dim on braking ?
Lights that dim on braking ?
Anyone ever consider a remedy to the head light dimming when braking ? I wonder if a capacitor added to the lighting coil circuit would help keep the voltage constant ? Any thoughts ?
https://www.youtube.com/watch?v=PFb6NU1giRA
"I prefer dangerous freedom over peaceful slavery." Thomas Jefferson
"I prefer dangerous freedom over peaceful slavery." Thomas Jefferson
Idea #1:
To use a capacitor, you will need to rectify the AC to DC before the capacitor. Since one side of the lighting coil is grounded, you will need a center tapped transformer to rectify both halves of the AC waveform to have enough current to light the bulb to full brightness. The capacitor would charge to peak voltage of the lighting coil (nearly 30 volts) therefore the capacitor must be kept small to keep it from blowing the light bulb at first contact. This circuit would only be used to feed the brake light/oil light circuit.
Idea #2:
A simpler approach would be to use a small sealed lead acid battery and a half wave rectifier. A regulator would be needed to prevent the battery from drawing too much current at the high voltage portions of the AC waveform and prevent the battery from venting from too much terminal voltage. The energy would be stored in the battery when running and then used when the brake light is activated. If a current limiter is used in the feed wire, activating the brake light would have no visible effect on the headlight. If you were going through all the trouble of building and installing this on a VMAX, you may want to run the headlight and hand warmers off the same regulated DC power source. All the lights and hand warmers would work even when the engine was not running.
Idea #3:
Another idea would be to run the headlight off the negative side of the AC waveform and the rest of the lights off the positive side. If I recall correctly, the oil guage check circuit will only work on the positive side. I doubt that this will work properly because it will rely on the cross polarity balance of the voltage regulator. I doubt that was a requirement when the regulator was built and I doubt that it would regulate well enough to do this. My guess is that when you turned on the brake lights, the headlight would get brighter or possibly burn out. It is hard to predict because I don't know the voltage regulator input filter delay.
Idea#4:
Take the lighting coil voltage and run it through a step up transformer to 120 to 240 VAC to power a Power Factor Corrected universal input switching power supply. This could then supply a regulated 14 volts to the lights. It would be more efficient than the SCR based regulator and it would attach right at the output of the lighting coil to the wiring harness. The original regulator could be retained but would no longer function as intended. Most switching regulators have large capacitors built into them and should not need any additional external capacitance. I would be concerned about vibration survivablity and contamination of the high voltage parts used in this idea.
Idea#5:
Install a single pole double throw relay to turn on a dummy brake light when the real brake light is off. When you apply the brake, the real one comes on and the dummy goes off. When you release the brake, the dummy comes on and the real one goes off. If you run the brake light switch to the relay you can put some resistors across the contacts so the light bulbs never really go out. They just go dim. This reduces the Cold Element Inrush current characteristic of light bulbs.
Idea#6:
Install an LED brakelight. They draw much less current and the dimming of the headlight will no longer be noticable.
Those are 6 ideas that were floating around in my head when I read the post. If I thought about it, I might come up with some more.
To use a capacitor, you will need to rectify the AC to DC before the capacitor. Since one side of the lighting coil is grounded, you will need a center tapped transformer to rectify both halves of the AC waveform to have enough current to light the bulb to full brightness. The capacitor would charge to peak voltage of the lighting coil (nearly 30 volts) therefore the capacitor must be kept small to keep it from blowing the light bulb at first contact. This circuit would only be used to feed the brake light/oil light circuit.
Idea #2:
A simpler approach would be to use a small sealed lead acid battery and a half wave rectifier. A regulator would be needed to prevent the battery from drawing too much current at the high voltage portions of the AC waveform and prevent the battery from venting from too much terminal voltage. The energy would be stored in the battery when running and then used when the brake light is activated. If a current limiter is used in the feed wire, activating the brake light would have no visible effect on the headlight. If you were going through all the trouble of building and installing this on a VMAX, you may want to run the headlight and hand warmers off the same regulated DC power source. All the lights and hand warmers would work even when the engine was not running.
Idea #3:
Another idea would be to run the headlight off the negative side of the AC waveform and the rest of the lights off the positive side. If I recall correctly, the oil guage check circuit will only work on the positive side. I doubt that this will work properly because it will rely on the cross polarity balance of the voltage regulator. I doubt that was a requirement when the regulator was built and I doubt that it would regulate well enough to do this. My guess is that when you turned on the brake lights, the headlight would get brighter or possibly burn out. It is hard to predict because I don't know the voltage regulator input filter delay.
Idea#4:
Take the lighting coil voltage and run it through a step up transformer to 120 to 240 VAC to power a Power Factor Corrected universal input switching power supply. This could then supply a regulated 14 volts to the lights. It would be more efficient than the SCR based regulator and it would attach right at the output of the lighting coil to the wiring harness. The original regulator could be retained but would no longer function as intended. Most switching regulators have large capacitors built into them and should not need any additional external capacitance. I would be concerned about vibration survivablity and contamination of the high voltage parts used in this idea.
Idea#5:
Install a single pole double throw relay to turn on a dummy brake light when the real brake light is off. When you apply the brake, the real one comes on and the dummy goes off. When you release the brake, the dummy comes on and the real one goes off. If you run the brake light switch to the relay you can put some resistors across the contacts so the light bulbs never really go out. They just go dim. This reduces the Cold Element Inrush current characteristic of light bulbs.
Idea#6:
Install an LED brakelight. They draw much less current and the dimming of the headlight will no longer be noticable.
Those are 6 ideas that were floating around in my head when I read the post. If I thought about it, I might come up with some more.
Holy shit! what is it that you do for a living joe?? i think you lost me on all of that but the LED brake light part 
but thats alright!!! maybe one of us should take the brake light bulb out tonight and see if the headlight stays bright.... i believe it will dim even without any bulb... all these batteries and transformers and regualtors and such make my head hurt 
but thats alright!!! maybe one of us should take the brake light bulb out tonight and see if the headlight stays bright.... i believe it will dim even without any bulb... all these batteries and transformers and regualtors and such make my head hurt My airbox is held on by one screw, not because Im lazy but because it is less weight!
Any questions or comments about this site itself can be directed to me at tylerochs@hotmail.com
Any questions or comments about this site itself can be directed to me at tylerochs@hotmail.com
Joe, Joe, Joe you're quite the asset to our forum ! Tyler and I tried the no tail ight trick tonight and wow we now have a bright headlight ! So, I ordered some led bulbs from E-bay and we'll let you know the outcome.
I figured the 12 led bulbs will take less wattage to run than the higher 19, 24 or 30 led bulbs ?
http://cgi.ebay.com/ebaymotors/ws/eBayI ... &viewitem=
1157 WHITE 12 LED LIGHT BULBS SUPER BRIGHT LED's
I figured the 12 led bulbs will take less wattage to run than the higher 19, 24 or 30 led bulbs ?
http://cgi.ebay.com/ebaymotors/ws/eBayI ... &viewitem=
1157 WHITE 12 LED LIGHT BULBS SUPER BRIGHT LED's
https://www.youtube.com/watch?v=PFb6NU1giRA
"I prefer dangerous freedom over peaceful slavery." Thomas Jefferson
"I prefer dangerous freedom over peaceful slavery." Thomas Jefferson
One question at a time..
My Job:
I work as an electrical engineer on AC and DC marine systems.
Back to the VMAX.
If the light still dims with the brake light out, then unplug the oil sensor plug. There is a path from the brake switch to the oil warning light that may be causing problems as well.
If you still have problems, there is a problem in the wiring harness.
Since the VMAX has no battery there is going to be a cold element surge when the brake light initially comes on. Is that transient event causing problems or is a longer term dim light problem that continues until the brake is released?
My Job:
I work as an electrical engineer on AC and DC marine systems.
Back to the VMAX.
If the light still dims with the brake light out, then unplug the oil sensor plug. There is a path from the brake switch to the oil warning light that may be causing problems as well.
If you still have problems, there is a problem in the wiring harness.
Since the VMAX has no battery there is going to be a cold element surge when the brake light initially comes on. Is that transient event causing problems or is a longer term dim light problem that continues until the brake is released?
With the tailight on the headlight dims as long as you are on the brakes.. leave up and the headlight gets brighter...
What determines the maxium output of a system, the Magnet strenght ? Remember the 83-84 Vmax's did not have a handwarmer coil and one was added in 85 with that tought in mind, could the lighting coil simply be rewound with heavier gauge wire or maybe more turns or a all together differnet coil? Thanks !
What determines the maxium output of a system, the Magnet strenght ? Remember the 83-84 Vmax's did not have a handwarmer coil and one was added in 85 with that tought in mind, could the lighting coil simply be rewound with heavier gauge wire or maybe more turns or a all together differnet coil? Thanks !
Last edited by Vmax540 on Wed Jan 28, 2009 11:08 pm, edited 1 time in total.
https://www.youtube.com/watch?v=PFb6NU1giRA
"I prefer dangerous freedom over peaceful slavery." Thomas Jefferson
"I prefer dangerous freedom over peaceful slavery." Thomas Jefferson
Since you are going to filter out the green and blue wavelengths with the red lens, it might make more sense to buy red LEDs. If I recall correctly, they are about 200% more efficient in light per watt.
I noticed that there were no specifications on the website about the brightness or current consumption. I am suspicious that maybe the red ones are just filtered white ones.
Either way, you may have solved the problem very quickly and easily.
Good choice.
I noticed that there were no specifications on the website about the brightness or current consumption. I am suspicious that maybe the red ones are just filtered white ones.
Either way, you may have solved the problem very quickly and easily.
Good choice.
One problem you may encounter.. The VMAX power system is AC. Most automotive systems are DC. The LEDs you selected MAY not operate on AC power. They may even be destroyed.
This possible limitation can be accomodated by putting a rectifier and a capacitor between the source and the load such that the load only sees DC. You will need two of these two piece circuits. One for the tail light and one for the brake light.
If I recall correctly, snowmobile specific LEDs are made to operate on AC as well as DC.
This possible limitation can be accomodated by putting a rectifier and a capacitor between the source and the load such that the load only sees DC. You will need two of these two piece circuits. One for the tail light and one for the brake light.
If I recall correctly, snowmobile specific LEDs are made to operate on AC as well as DC.
The maximum output of a coil is determined by:
1. The strength of the magnets.
2. The number of magnets (poles)
3. The speed of the magnets (RPM*number of poles)
4. The number of turns around the core (volts per turn per RPM)
5. The magnetic gap length (magnetic resistance)
6. The magnetic gap area (magnetic resistance)
7. The cross sectional area of the wire (electrical resistance)
8. The length of the wire.(electrical resistance)
I don't recall the magnetic units from college. I would have to go look them up.
The first four are multiplied together to determine the electrical potential available.
The next two pairs are multiplied separately and then added to get the total resistance.
The power available is the product of the first four divided by the sum of the last two pairs.
I believe that the magnetic resistance is larger than the electrical resistance therefore putting larger wire on the existing core would provide only a small gain in power.
I believe you need to install a larger core (like the CDI core) and put approximately the same number of turns as the current lighting coil. I doubt the CDI core will fit at the location of the lighting coil as the stator is now configured.
If I recall correctly, the CDI core has about 3 times the magnetic cross section and will drop the magnetic resistance significantly.
If you want to get more power out of the lighting coil, you will need to install a larger core with slightly larger wire and slightly more turns.
I don't recall the order of the cores, but there was significant wasted space around the stator assembly for more core and more wire.
It is also possible to use two coils in series to provide more voltage and/or make space for more wire.
Somebody could really have some fun with this coming up with an update kit.
1. The strength of the magnets.
2. The number of magnets (poles)
3. The speed of the magnets (RPM*number of poles)
4. The number of turns around the core (volts per turn per RPM)
5. The magnetic gap length (magnetic resistance)
6. The magnetic gap area (magnetic resistance)
7. The cross sectional area of the wire (electrical resistance)
8. The length of the wire.(electrical resistance)
I don't recall the magnetic units from college. I would have to go look them up.
The first four are multiplied together to determine the electrical potential available.
The next two pairs are multiplied separately and then added to get the total resistance.
The power available is the product of the first four divided by the sum of the last two pairs.
I believe that the magnetic resistance is larger than the electrical resistance therefore putting larger wire on the existing core would provide only a small gain in power.
I believe you need to install a larger core (like the CDI core) and put approximately the same number of turns as the current lighting coil. I doubt the CDI core will fit at the location of the lighting coil as the stator is now configured.
If I recall correctly, the CDI core has about 3 times the magnetic cross section and will drop the magnetic resistance significantly.
If you want to get more power out of the lighting coil, you will need to install a larger core with slightly larger wire and slightly more turns.
I don't recall the order of the cores, but there was significant wasted space around the stator assembly for more core and more wire.
It is also possible to use two coils in series to provide more voltage and/or make space for more wire.
Somebody could really have some fun with this coming up with an update kit.
mmmm shoot... didnt take into consideration the AC/DC with the LEDs... know of any wholesale places that sell rectifiers cheap and small?
My airbox is held on by one screw, not because Im lazy but because it is less weight!
Any questions or comments about this site itself can be directed to me at tylerochs@hotmail.com
Any questions or comments about this site itself can be directed to me at tylerochs@hotmail.com
Hmmmm....,. maybe these will work ?
http://cgi.ebay.com/ebaymotors/Rotating ... ccessories
If not do I simply need a 12v diode in series with the bulb and a small (?) capacitor in parallel across the diode to make a DC bulb work ? Thanks Again !
http://cgi.ebay.com/ebaymotors/Rotating ... ccessories
If not do I simply need a 12v diode in series with the bulb and a small (?) capacitor in parallel across the diode to make a DC bulb work ? Thanks Again !
https://www.youtube.com/watch?v=PFb6NU1giRA
"I prefer dangerous freedom over peaceful slavery." Thomas Jefferson
"I prefer dangerous freedom over peaceful slavery." Thomas Jefferson
From your ideas, I can tell we don't share the same concept of how the system operates.
Here is a photo of a disassembled stator.
The largest coil (on the left) is the lighting coil. It has a Yellow wire soldered to the bottom end, and the top end of the coil is soldered to a ground lug. A black wire attaches to the ground lug. It is shown to the left of the lighting coil.
The warmer coil is the one on the right with the wire going out the right side if the frame. One end of the coil is grounded and the other is shown. The wire is Yellow/Black but it is difficult to see in the photo.
The other two loose coils are the CDI charge coils. The Red wire connects to both of them although it is not connected in the photo. The Brown wire is connected to the larger coil and the White/Red is connected to the smaller coil.
The coil attached to the baseplate is the pickup coil. It has one end grounded and the free end is connected to the White/Green wire.
The grip warmer circuit is simplest. I will describe it first.
The open circuit output voltage of the warmer coil can be described by a constant called the Voltage to Frequency ratio. Basically, the faster the engine turns, the higher the frequency and the higher the voltage across the coil. Since there is no regulator in the circuit, the waveshape follows the derivative of the contour of magnetic field in the rotor. The magnets can be designed to give a sine, square, or triangle wave shape. If I recall correctly, Yamaha typically uses a square wave on their magnets. I'm not sure. Don't quote me.
The loaded voltage is the open circuit voltage divided by [the sum of the a) internal magnetic resistance, b) the internal copper resistance, and c) the external load resistance] and multiplied by [the external load resistance].
The voltage and frequency vary with RPM. At 7500 RPM, the voltage is 5 times the voltage at 1500 RPM. If I recall correctly, the voltage at 1500 RPM is about 5 volts, therefore it should be about 25 volts at 7500 RPM. I don't recall if this is with the warming coils on or off. The waveform is a flat topped sine wave because of the magnetic field contour. The peak voltage can be 40 volts both positive and negative.
This head cold is whipping my brain function down to some low levels I have not experienced in a long time. I have never coughed so hard and long. I need to take my meds and a nap before finishing this post.
Stand by.
Here is a photo of a disassembled stator.
The largest coil (on the left) is the lighting coil. It has a Yellow wire soldered to the bottom end, and the top end of the coil is soldered to a ground lug. A black wire attaches to the ground lug. It is shown to the left of the lighting coil.
The warmer coil is the one on the right with the wire going out the right side if the frame. One end of the coil is grounded and the other is shown. The wire is Yellow/Black but it is difficult to see in the photo.
The other two loose coils are the CDI charge coils. The Red wire connects to both of them although it is not connected in the photo. The Brown wire is connected to the larger coil and the White/Red is connected to the smaller coil.
The coil attached to the baseplate is the pickup coil. It has one end grounded and the free end is connected to the White/Green wire.
The grip warmer circuit is simplest. I will describe it first.
The open circuit output voltage of the warmer coil can be described by a constant called the Voltage to Frequency ratio. Basically, the faster the engine turns, the higher the frequency and the higher the voltage across the coil. Since there is no regulator in the circuit, the waveshape follows the derivative of the contour of magnetic field in the rotor. The magnets can be designed to give a sine, square, or triangle wave shape. If I recall correctly, Yamaha typically uses a square wave on their magnets. I'm not sure. Don't quote me.
The loaded voltage is the open circuit voltage divided by [the sum of the a) internal magnetic resistance, b) the internal copper resistance, and c) the external load resistance] and multiplied by [the external load resistance].
The voltage and frequency vary with RPM. At 7500 RPM, the voltage is 5 times the voltage at 1500 RPM. If I recall correctly, the voltage at 1500 RPM is about 5 volts, therefore it should be about 25 volts at 7500 RPM. I don't recall if this is with the warming coils on or off. The waveform is a flat topped sine wave because of the magnetic field contour. The peak voltage can be 40 volts both positive and negative.
This head cold is whipping my brain function down to some low levels I have not experienced in a long time. I have never coughed so hard and long. I need to take my meds and a nap before finishing this post.
Stand by.
Last edited by Joe on Fri Jan 30, 2009 2:14 pm, edited 1 time in total.
Hope you get better soon....!
https://www.youtube.com/watch?v=PFb6NU1giRA
"I prefer dangerous freedom over peaceful slavery." Thomas Jefferson
"I prefer dangerous freedom over peaceful slavery." Thomas Jefferson
Tht symptoms let up briefly, so I will try to finish my description...
The warmer circuit has two states: On and Off, therefore it needs no regulator.
The lighting circuit has MANY more states: Headlight Off, low beam, high beam, Brake light off, brake light on, oil light on, oil light off, and the combinations of those. It also has to deal with transitions in the load and trying to keep the light bulbs from burning out. Keeping the lights on brightly all the time is the goal.
To meet that goal, a regulator is needed. Page 7-12 of the Owners Service Manual shows the regulation specification for the system. The corner of the voltage plot indicates the sytem reaches 15 volts at 2500 RPM. That means the coil should be making 6 volts per 1000 RPM. Above 2500 RPM the regulator is active and is trying to hold the voltage down to 15 volts according to the graph. The next block down, the regulator specification says it is a shorting type that is regulating to 13.3 to 14.3 volts. I hate disagreement in specification sheets. This is a case where the difference can be attributed to the wiring resistance between the lighting coil and the regulator. The regulator needs to be set a half to a full volt lower than necessary to make up for the voltage losses in the wiring harness.
The way a shorting regulator works is that it has a voltage sensor that measures the average voltage over a period of time and then shorts the output to ground when the average gets too high. This is a very common regulator on magneto driven lighting systems. The short gets removed every time the voltage changes polarity. In the case of the VMAX system, it reverses four times for every revolution of the crankshaft. The thermal intertia of the bulbs attenuate the modulation to near imperceptible levels. That is fast enough that most humans cannot perceive the regulation visually.
LEDs respond fast enough that we will probably see the modulator regulation. It will be expecially obvious if the eye scans past the LED while it is on. Instead of seeing a red line, it will produce a line of dots where the LED was when it was on, but no light when it was off.
The lighting coil should make 45 RMS AC volts at 7500 RPM. In order for the regulator to hold the system voltage down to 15 volts, it will need to be shorted to ground about 67% of the time. With a 33% duty cycle, the peak voltage will reach about 45 VDC before the regulator fires.
Every turn of the engine will produce the following waveshape on the regulated lighting wire:
0 degrees = voltage changes phase = crosses zero
========= voltage starts ramping at 0 volts and ramps up to 45 volts DC
30 degrees = reguilator fires at 45 VDC
========= voltage shorted to ground, voltage at about 1 volt due to wiring losses
90 degrees = voltage changes phase = crosses zero
========= voltage starts ramping at 0 volts and ramps down to -45 volts DC
120 degrees = reguilator fires at -45 VDC
========= voltage shorted to ground, voltage at about -1 volt due to wiring losses
180 degrees = voltage changes phase = crosses zero
========= voltage starts ramping at 0 volts and ramps up to 45 volts DC
210 degrees = reguilator fires at 45 VDC
========= voltage shorted to ground, voltage at about 1 volt due to wiring losses
270 degrees = voltage changes phase = crosses zero
========= voltage starts ramping at 0 volts and ramps down to -45 volts DC
310 degrees = reguilator fires at -45 VDC
========= voltage shorted to ground, voltage at about -1 volt due to wiring losses
360 degrees = voltage changes phase = crosses zero
The waveform is complicated at this point.
It is techincally Alternating Current because the polarity changes four times per revolution.
It is technically Regulated because the lights do not burn out when connected to the coil that puts out 45 volts at 7500 RPM.
The detail that is not obvious is the high crest factor of the signal. That is the peak voltage relative to the RMS voltage.
A 15 volt RMS sine wave has a peak voltage of 21 volts. This waveform has a peak voltage of 45 volts. When people rate AC systems they generally think only of sine waves. They don't typically take into consideration these high crest factor AC signals.
The LED tail light that you chose needs to survive:
1. The +45 volt DC of the positive part of the waveform. Most of the inexpensive electronic regulators are not expected to work above 40 volts,
2. The -45 volt DC of the negative part of the waveform. Most LEDs fail with about 7 to 9 volts in reverse. These packages products MAY be protected from reverse polarity by the design, but that is an extra nickel of cost that the producer may have chose not to spend.
In order for the LED to put out full brightness, it needs a continuous input current and typically more than 10 volts. I doubt that there is much energy storage inside of the base of those bulbs. The wave form is over +10 volts for only 26 degress of rotation twice every 360 degrees of crankshaft rotation. That is less than a 15% duty cycle. We have no specification on how long the voltage needs to be on before the LED comes on. This is governed by the design of the current regulator inside the bulb.
Maybe you get the idea that I give this a low probablility of success. You would be right. I like high probability projects and this is not one of them.
To do this right will require storage of electrical energy to keep the LED on during the dark periods of the lighting waveform. The LEDs only need positive voltage therefore we can completely ignore the negative half of the waveform for producing power for the LED. This can be done with a single rectifier diode and a single capacitor. Both need to be rated for at least 50 volts. 100 volts should give adequate overhead.
The second thing we need is a DC regulator to limit the voltage to what the LEDs can handle. My favorite is the TL783 from TI.com. They will send out free samples to new customers. This is very handy and cheap. The regulator will need two trimming resistors to set the output voltage to about 13 to 15 volts. since we are designing this thing, we can use any target voltage we want.
I would propose that the regulator circuit be connected between the bLue and the Black wires at the tail light to keep the capacitor charged whenever the engine is running. This would keep the tail light on all the time like it is now.
We can add a relay or switch to connect the brake light portion of the LED to the DC power when the Green/Yellow wire goes active.
Proposed location of new circuit board: between the tail light base and the seat.
Connection to existing circuit: Installs between existing bullet connectors inside seat back frame.
Cost of parts:
Diode $0.10
Capacitor $0.50
Regulator $1.25
Resistors 2 x$0.05
Relay $2.00
================
Total parts $3.90
If the relay chosen needs protection from the reversing input voltage, one more diode, capacitor, and resistor will be needed. ($0.65)
Assuming we need the protection, the electronics parts cost about $4.55.
Now comes the expensive stuff.
We need a circuit board designed.
We need to get circuit boards fabricated.
We need bullet connectors and appropriately colored wire.
We need to order and verify the parts will work.
We need to assemble the boards.
We need to test the boards in the shop.
We need to test the boards in the field.
The warmer circuit has two states: On and Off, therefore it needs no regulator.
The lighting circuit has MANY more states: Headlight Off, low beam, high beam, Brake light off, brake light on, oil light on, oil light off, and the combinations of those. It also has to deal with transitions in the load and trying to keep the light bulbs from burning out. Keeping the lights on brightly all the time is the goal.
To meet that goal, a regulator is needed. Page 7-12 of the Owners Service Manual shows the regulation specification for the system. The corner of the voltage plot indicates the sytem reaches 15 volts at 2500 RPM. That means the coil should be making 6 volts per 1000 RPM. Above 2500 RPM the regulator is active and is trying to hold the voltage down to 15 volts according to the graph. The next block down, the regulator specification says it is a shorting type that is regulating to 13.3 to 14.3 volts. I hate disagreement in specification sheets. This is a case where the difference can be attributed to the wiring resistance between the lighting coil and the regulator. The regulator needs to be set a half to a full volt lower than necessary to make up for the voltage losses in the wiring harness.
The way a shorting regulator works is that it has a voltage sensor that measures the average voltage over a period of time and then shorts the output to ground when the average gets too high. This is a very common regulator on magneto driven lighting systems. The short gets removed every time the voltage changes polarity. In the case of the VMAX system, it reverses four times for every revolution of the crankshaft. The thermal intertia of the bulbs attenuate the modulation to near imperceptible levels. That is fast enough that most humans cannot perceive the regulation visually.
LEDs respond fast enough that we will probably see the modulator regulation. It will be expecially obvious if the eye scans past the LED while it is on. Instead of seeing a red line, it will produce a line of dots where the LED was when it was on, but no light when it was off.
The lighting coil should make 45 RMS AC volts at 7500 RPM. In order for the regulator to hold the system voltage down to 15 volts, it will need to be shorted to ground about 67% of the time. With a 33% duty cycle, the peak voltage will reach about 45 VDC before the regulator fires.
Every turn of the engine will produce the following waveshape on the regulated lighting wire:
0 degrees = voltage changes phase = crosses zero
========= voltage starts ramping at 0 volts and ramps up to 45 volts DC
30 degrees = reguilator fires at 45 VDC
========= voltage shorted to ground, voltage at about 1 volt due to wiring losses
90 degrees = voltage changes phase = crosses zero
========= voltage starts ramping at 0 volts and ramps down to -45 volts DC
120 degrees = reguilator fires at -45 VDC
========= voltage shorted to ground, voltage at about -1 volt due to wiring losses
180 degrees = voltage changes phase = crosses zero
========= voltage starts ramping at 0 volts and ramps up to 45 volts DC
210 degrees = reguilator fires at 45 VDC
========= voltage shorted to ground, voltage at about 1 volt due to wiring losses
270 degrees = voltage changes phase = crosses zero
========= voltage starts ramping at 0 volts and ramps down to -45 volts DC
310 degrees = reguilator fires at -45 VDC
========= voltage shorted to ground, voltage at about -1 volt due to wiring losses
360 degrees = voltage changes phase = crosses zero
The waveform is complicated at this point.
It is techincally Alternating Current because the polarity changes four times per revolution.
It is technically Regulated because the lights do not burn out when connected to the coil that puts out 45 volts at 7500 RPM.
The detail that is not obvious is the high crest factor of the signal. That is the peak voltage relative to the RMS voltage.
A 15 volt RMS sine wave has a peak voltage of 21 volts. This waveform has a peak voltage of 45 volts. When people rate AC systems they generally think only of sine waves. They don't typically take into consideration these high crest factor AC signals.
The LED tail light that you chose needs to survive:
1. The +45 volt DC of the positive part of the waveform. Most of the inexpensive electronic regulators are not expected to work above 40 volts,
2. The -45 volt DC of the negative part of the waveform. Most LEDs fail with about 7 to 9 volts in reverse. These packages products MAY be protected from reverse polarity by the design, but that is an extra nickel of cost that the producer may have chose not to spend.
In order for the LED to put out full brightness, it needs a continuous input current and typically more than 10 volts. I doubt that there is much energy storage inside of the base of those bulbs. The wave form is over +10 volts for only 26 degress of rotation twice every 360 degrees of crankshaft rotation. That is less than a 15% duty cycle. We have no specification on how long the voltage needs to be on before the LED comes on. This is governed by the design of the current regulator inside the bulb.
Maybe you get the idea that I give this a low probablility of success. You would be right. I like high probability projects and this is not one of them.
To do this right will require storage of electrical energy to keep the LED on during the dark periods of the lighting waveform. The LEDs only need positive voltage therefore we can completely ignore the negative half of the waveform for producing power for the LED. This can be done with a single rectifier diode and a single capacitor. Both need to be rated for at least 50 volts. 100 volts should give adequate overhead.
The second thing we need is a DC regulator to limit the voltage to what the LEDs can handle. My favorite is the TL783 from TI.com. They will send out free samples to new customers. This is very handy and cheap. The regulator will need two trimming resistors to set the output voltage to about 13 to 15 volts. since we are designing this thing, we can use any target voltage we want.
I would propose that the regulator circuit be connected between the bLue and the Black wires at the tail light to keep the capacitor charged whenever the engine is running. This would keep the tail light on all the time like it is now.
We can add a relay or switch to connect the brake light portion of the LED to the DC power when the Green/Yellow wire goes active.
Proposed location of new circuit board: between the tail light base and the seat.
Connection to existing circuit: Installs between existing bullet connectors inside seat back frame.
Cost of parts:
Diode $0.10
Capacitor $0.50
Regulator $1.25
Resistors 2 x$0.05
Relay $2.00
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Total parts $3.90
If the relay chosen needs protection from the reversing input voltage, one more diode, capacitor, and resistor will be needed. ($0.65)
Assuming we need the protection, the electronics parts cost about $4.55.
Now comes the expensive stuff.
We need a circuit board designed.
We need to get circuit boards fabricated.
We need bullet connectors and appropriately colored wire.
We need to order and verify the parts will work.
We need to assemble the boards.
We need to test the boards in the shop.
We need to test the boards in the field.
I was thinking about it last night and realized that the relay is overkill. It can be done with a $0.25 transistor instead of a $2 relay.
The rectifier and capacitor on the brake input line are necessary to prevent filcker in the brake light when the engine is at idle. A voltage doubler (two diodes instead of one) would also allow the brake light to come on at less than 1800 RPM. The braking capacitor does not need to be the $0.50 kind. It can be the $0.10 kind.
If anyone is interested in building one of these, let me know. I can run it through the circuit simulator and verify it works before puiblishing a schematic and parts list.
The rectifier and capacitor on the brake input line are necessary to prevent filcker in the brake light when the engine is at idle. A voltage doubler (two diodes instead of one) would also allow the brake light to come on at less than 1800 RPM. The braking capacitor does not need to be the $0.50 kind. It can be the $0.10 kind.
If anyone is interested in building one of these, let me know. I can run it through the circuit simulator and verify it works before puiblishing a schematic and parts list.