Anybody have experience with a DIY solution for converting AC vehicle lighting to LED?
The vehicle is a 1980 Honda dirt bike, with a 6V 45W alternator, and a reputation for burning bulbs. The electrical system is AC; schematic attached. The light bulb load is 25W + 3W + 3W.
I think it might be better to covert everything to DC and use LED bulbs, rather than tracking down 6V incandescent bulbs to fit the original sockets. I've googled a bit, but couldn't find anybody who tried this on a 6V AC system.
I think I just need a bridge, capacitor, and resistor (to avoid thermal runaway). Do you think a regulator would be wise? Any tips, such as the voltage rating for the capacitor? I have no idea what the waveform out of a 6V alternator would look like.
The vehicle is a 1980 Honda dirt bike, with a 6V 45W alternator, and a reputation for burning bulbs. The electrical system is AC; schematic attached. The light bulb load is 25W + 3W + 3W.
I think it might be better to covert everything to DC and use LED bulbs, rather than tracking down 6V incandescent bulbs to fit the original sockets. I've googled a bit, but couldn't find anybody who tried this on a 6V AC system.
I think I just need a bridge, capacitor, and resistor (to avoid thermal runaway). Do you think a regulator would be wise? Any tips, such as the voltage rating for the capacitor? I have no idea what the waveform out of a 6V alternator would look like.
Attachments
Interesting problem. I watched a coworker change out almost every light in his Toyota to LED, and it was easy, because it's a 12V DC system. I don't think I've seen anything for 6V. And yes, you'd want some sort of rectification to DC, even if it's just a diode in series with the LED. They don't like AC (unlike othe diodes). Probably even a smoothing cap. A current limiting resistor is a must, if the LED assemble does not have it built in.
Voltage regulator? Probably not. But you would want to measure the voltage at higher RPMs to see what you are actually getting, and plan limit resistors from there.
I'm sure others will have some more practical ideas. Keep us posted.
Voltage regulator? Probably not. But you would want to measure the voltage at higher RPMs to see what you are actually getting, and plan limit resistors from there.
I'm sure others will have some more practical ideas. Keep us posted.
Hey Tony,
Your system doesn't already have a rectifier in it?
What about something like this?
https://www.amazon.com/Amico-Single-Bridge-Rectifier-KBPC5010/dp/B008DEU18G
Or just go to your local bike shop, I'm sure they'll have something.
Your system doesn't already have a rectifier in it?
What about something like this?
https://www.amazon.com/Amico-Single-Bridge-Rectifier-KBPC5010/dp/B008DEU18G
Or just go to your local bike shop, I'm sure they'll have something.
Thanks for your input guys. Yes, I'm sure it's 6V AC and there's no rectifier.
Problem with a project like this is there's many ways to go, not just electrical but mechanical as well.
I think I'll try to use a voltage doubler and try to regulate to 12VDC. That way I can buy replacement lights as complete assemblies rather than trying to put a new bulb mount in an old fixture.
I'm gonna try it with some 1N5822 diodes, 1,000uF/50V caps, and a LM2940-12 regulator. I read something that suggested regulating LEDs to 12VDC even though cars are about 14VDC when running, and another thing that suggested being generous with cap voltage rating.
Problem with a project like this is there's many ways to go, not just electrical but mechanical as well.
I think I'll try to use a voltage doubler and try to regulate to 12VDC. That way I can buy replacement lights as complete assemblies rather than trying to put a new bulb mount in an old fixture.
I'm gonna try it with some 1N5822 diodes, 1,000uF/50V caps, and a LM2940-12 regulator. I read something that suggested regulating LEDs to 12VDC even though cars are about 14VDC when running, and another thing that suggested being generous with cap voltage rating.
Cars are about 14V when running because they need the extra volts to charge the battery. If your bike is batteryless, the output may be 6V and no extra.
LEDs are tough. And they emit roughly the same amount of light be it at 50% of rated DC current or 100%. So your instantaneous voltage doesn't have to be too stable.
A voltage doubler, and an RC filter - for voltage stabilizing as well as current-limiting and good to go.
Regulator doesn't work unless the input voltage is consistently a few volts above the output voltage. And it wastes power unnecessarily.
LED power is controlled by current, not voltage. 12VDC rated modules have a resistor.
LEDs are tough. And they emit roughly the same amount of light be it at 50% of rated DC current or 100%. So your instantaneous voltage doesn't have to be too stable.
A voltage doubler, and an RC filter - for voltage stabilizing as well as current-limiting and good to go.
Regulator doesn't work unless the input voltage is consistently a few volts above the output voltage. And it wastes power unnecessarily.
LED power is controlled by current, not voltage. 12VDC rated modules have a resistor.
Oh KDX's are nice bikes, my friend has a KDX185 that I rode a bit.
This bike is an oh so old 1980 XR200, as in dual shocks.
If your KDX is newer you can google on fancier things you can do like using stock components from other years or other models to make a nice lighting system.
That didn't really appeal to me. This is a cheap bike, the original rear taillight is missing and the headlight burned out from 2 owners ago. I want a cheap and easy fix. I am just OCD enough that the hole in the rear fender and burned out headlight bother me, but not OCD enough to turn it into a big resto-mod project.
This bike is an oh so old 1980 XR200, as in dual shocks.
If your KDX is newer you can google on fancier things you can do like using stock components from other years or other models to make a nice lighting system.
That didn't really appeal to me. This is a cheap bike, the original rear taillight is missing and the headlight burned out from 2 owners ago. I want a cheap and easy fix. I am just OCD enough that the hole in the rear fender and burned out headlight bother me, but not OCD enough to turn it into a big resto-mod project.
I had a Suzuki SP370 years ago. It had 6V DC electrics. The alternator coil wiring was like your bike. One side of the coil was grounded.
The SP 370 6V electrical system had a half wave rectifier.
I rewired the coil removing the ground tab and replacing it with extra wire.
This allowed me to fit a single phase 12V rectifier regulator from a Honda trial bike and a small 12V battery. This ran conventional bulbs and was far better than the original 6V system.
In your case the electrics are super simple. But now we have the additional complication of wanting to use LED lights.
I built a rear light for a 12v trial bike recently I used a decent fibreglass strip board, and added banks of high brightness LEDs and dropper resistors to run on 12V. I coated the PCB with a conformal coating to stop corrosion.
What you need to do to get your bike electrics running OK depends on what voltage the alternator coils is outputting. There are plenty of aftermarket rectifier / regulators available If you add an extra wire to the alternator coil to replace the ground tab you could use one. They are available in 6Volt and 12Volt versions. They can usually be used with a capacitor instead of a battery. This would give you a decent regulated DC supply for your lights.
The SP 370 6V electrical system had a half wave rectifier.
I rewired the coil removing the ground tab and replacing it with extra wire.
This allowed me to fit a single phase 12V rectifier regulator from a Honda trial bike and a small 12V battery. This ran conventional bulbs and was far better than the original 6V system.
In your case the electrics are super simple. But now we have the additional complication of wanting to use LED lights.
I built a rear light for a 12v trial bike recently I used a decent fibreglass strip board, and added banks of high brightness LEDs and dropper resistors to run on 12V. I coated the PCB with a conformal coating to stop corrosion.
What you need to do to get your bike electrics running OK depends on what voltage the alternator coils is outputting. There are plenty of aftermarket rectifier / regulators available If you add an extra wire to the alternator coil to replace the ground tab you could use one. They are available in 6Volt and 12Volt versions. They can usually be used with a capacitor instead of a battery. This would give you a decent regulated DC supply for your lights.
Mine is an old slugger 400 that was all gone over. Had a couple XRs and an XL. I actually learned how to ride manual transmission on an XL. Then I acquired a taste for two strokes and had a few of those over the years, and a honda 250R triple and some street bikes. Broke my neck a while back swore I'd never ride another motorcycle, I guess until my rebirth lol. New rule street bikes only. I feel crotch rockets are safe and I trust myself on them. My *** will never see another modern two stroke race bike seat. Thats a personal rule I have stuck by.
Single-LED MR11 and MR16 lamps will often work down to 6 volts. They have full wave rectifiers and constant-current switching regulators so they're OK with AC or DC and a wide range of voltage. If they don't fit the bill as-is, you could use them as drivers, or just buy the modules from Dealextreme.
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