MTFCA Forum

I noticed the topic of LED headlamp bulbs has come up a few times.


This is something that is available here in Australia. I purchased a pair last year but haven't fitted them yet. I'll post an update to this thread once I have. I expect beam adjustment (focus and tilt) will be more critical than it is with incandescent bulbs. One of the tests I plan to do is to leave them switched on and see how long it takes to drain a fully charged 6 Volt Optima redtop.

http://www.classicandvintagebulbs.com/page6.html

http://www.classicandvintagebulbs.com/page9.html

I have no affiliation with this company.

John, we were typing at the same time !!
Check out my thread also about LED bulbs.

Ruxstel24 wrote: ↑

Fri Feb 01, 2019 6:15 pm

John, we were typing at the same time !!
Check out my thread also about LED bulbs.

More info on LEDS in these posts from Dave (Ruxstel24)
viewtopic.php?f=2&t=1013&p=7234#p7234

viewtopic.php?f=2&t=96&p=6405#p6405

Yep, awaiting your report also John.
You don't have weather for an excuse, unless it's too hot !

AdminJeff wrote: ↑

Fri Feb 01, 2019 6:34 pm

Ruxstel24 wrote: ↑

Fri Feb 01, 2019 6:15 pm

John, we were typing at the same time !!
Check out my thread also about LED bulbs.

More info on LEDS in these posts from Dave (Ruxstel24)
viewtopic.php?f=2&t=1013&p=7234#p7234

viewtopic.php?f=2&t=96&p=6405#p6405

Jeff, if John doesn't mind, I would be fine with combining the two threads.

Combining the threads sounds like a great idea.

Ok now you’re testing me, right? I can do it but it’s date nite with my wife and all I have is my iPhone which is next to impossible to manage from. It’ll have to wait until I get home on my Mac. Or tomorrow depending on how well date nite goes...

Jefg

AdminJeff wrote: ↑

Fri Feb 01, 2019 8:42 pm

Ok now you’re testing me, right? I can do it but it’s date nite with my wife and all I have is my iPhone which is next to impossible to manage from. It’ll have to wait until I get home on my Mac. Or tomorrow depending on how well date nite goes...

Jefg

You just take care of the lady tonight...
You can earn your big bucks tomorrow !!

The ones I got are 6V-24V positive or negative ground...from ledlight.com

The Model A forum on Fordbarn? That place is tiger country.

Do you guys figure if the bulbs are 6v-24v could they work for the folks that have magneto headlights? Jim

Model A side of fordbarn? LOL muppet country you mean.

TFan wrote: ↑

Fri Feb 01, 2019 11:37 pm

Do you guys figure if the bulbs are 6v-24v could they work for the folks that have magneto headlights? Jim

I used to try & make my own LED bulbs. Have a feeling i tested that but i can't be bothered testing it tonight. I'll tinker with some of my bulbs and let you know the results in ...24 hours?

I have been testing some of the LED bulbs from Classic and Vintage Bulbs. First thing to note is that old reflectors are a waste of time with them (or incandescent bulbs). New reflectors make a world of difference. The bulb positioning is important so that the beam points correctly with respect to low beam (it needs to point down) and high beam (it points straight ahead). Because of the symmetrical base, the bulb will fit in two positions, but only one is correct. In my instance I had to reverse one of the plugs at the back of the headlight so that high beam is activated when "Bright" is selected on the headlight switch. The focusing adjustment seems to be somewhat more definite than with the incandescent bulbs. The most noticeable difference is the whiter light. The difference between high and low beam seems more obvious than with the incandescent bulbs (but note that repro bulbs don't have the correct filament position anyway). Also, there's a huge drop in the current consumption of course; in theory a pair would run on high beam for about 40 hours with no charging. I did a quick test with a variable power supply which showed the bulbs have a proper switchmode driver for the LED's, not just a dropping resistor. If the input voltage drops too much (as I found when using the starter motor) the LED's simply stop working altogether.
I've become quite used to these bulbs and I do think they're an improvement for those that drive at night.

John, my reflectors, while not new, are pretty decent.
Here's a couple shots of just sunshine, you can see the bulb through the H glass, kinda.

I played around a little against the garage door today (inside), and the focus I had adjusted with the sockets all the way forward. I think that's about the best you can get.

I don't drive that much at night, but if you get caught up with something and wind up driving home after dark...it's nice to see and be seen

TFan wrote: ↑

Fri Feb 01, 2019 11:37 pm

Do you guys figure if the bulbs are 6v-24v could they work for the folks that have magneto headlights? Jim

Ok i tested just one bulb with magneto headlights. They light up dimly at idle, and get brighter at speed. At full speed i fear the resistance starts dropping & they'll burn out so you may want to consider wiring a bulb in series as a resistor. I'm not an electrical guru so i don't know if you'd need a 6,9,12 or 24 volt bulb.
If you had the lights in series like magneto lights tend to be, I'd imagine you'd need a few more RPM to keep them lit.
If nothing else, try it & let us know.

These bulbs look befitting
Note the circuit diagram for them.

I'm a little confused...OK I'm always a lot confused. If the magneto is A/C, do the LEDs have a built in rectifier to use the reverse polarity? If not, you could wire up the four diodes and get twice the brightness. You could also wire up the headlamps for series and parallel with a switch to select between the two. Parallel for low RPM and Series for high but I imagine no one would bother to want to make that or have to fool with remembering to throw the switch. Our '26 has a battery so this is more academic than anything.

varmint wrote: ↑

Sat Feb 02, 2019 10:42 pm

If the magneto is A/C, do the LEDs have a built in rectifier to use the reverse polarity?

LED bulbs generally have at least one diode for protection against reverse polarity. Some have a bridge rectifier which enables them to work with either polarity. In theory they will work on AC, but are not designed to do so. For one thing, a large electrolytic filter capacitor is required to smooth the rectified output from the diode(s). This not required for DC operation, and there isn't enough room inside a normal car bulb to fit one. Bulbs fitted with one diode are worse off on AC as the "rectifier' is working only in half wave. I would expect some flicker to be evident when operating off a magneto at low revs. My main concern is how well the LED driver will tolerate being fed with an unfiltered rectified waveform. Also, at high revs, a good magneto might put out 30Vrms. But being an AC waveform resembling something between a sine and triangle wave, the peak will be higher than that. Then there's the question of spikes coming down the supply from the ignition coils and how they might affect the delicate solid state LED driver.
LED bulbs would be best used with an external regulator if magneto operation is required.

The electronics are possible to convert the wide range of magneto output into a steady DC 6v but if you are going that far then it might be better to convert the output to DC 12v where all kinds of LED options would be available. Essentially a watertight box. What might be even easier is just to get a 12v battery for the LED headlights as it should last a long time on a single charge.

I finally tried out my 6 volt LED headlight bulbs. They light up the road really well.

This design points the light sideways and uses the reflectors to point the light forward which I think gives better control and avoids dazzling on-coming drivers.

I'm still using original Ford 21-3 candlepower bulbs. They work great in the dark, but not so well on lighted city streets. I'm not interested in putting a 50 candle power bulb in, but would like maybe a 32 cp. I can't seem to find any.

Larry. Snyder's lists a 6 volt 32/32cp bulb. part # A-13007-C in their 2020 catalog. $1.45 If You can't find one You can use the 32/50 CP bulb rotate it 180 deg So 32cp filament is on the bright or on switch position Your choice. and don't use the 50 cp Filament section. to save Your generator.

I'm a bit confused. A diode is by definition a one-way electrical device; it's whole purpose is to allow electrons to flow in only one direction. LED stands for light emitting diode (with emphasis on diode). How can a LED operate on AC without constant flickering? I do realize that the flickering would be very fast, but I would think that the net effect would be dimmer LEDs on mag as opposed to bat. Does the higher voltage on mag offset the flickering?
I honestly don't know. Could someone enlighten me (pun intended) ?

A diode is by definition a one-way electrical device...

Yes. It's really OT for this discussion, but everybody should be made aware of this. While a diode is one-way, higher voltage than it's designed to handle can overpower it and send current the wrong way. Don't let the magneto wire or anything connected to it, like a charger wire, get within ½" of high voltage (spark plug wire).

John Codman wrote: ↑

Mon Dec 06, 2021 10:21 am

How can a LED operate on AC without constant flickering?

John,

There's a long answer to this, but let's stick to the short one for now ... AC LED lamps will typically contain a rectifier, and may also contain a capacitor and driver. These things effectively change the AC to DC, allowing the LED to operate as you need.

With particular regard to flickering; the capacitor will tend to smooth out any ripple in the DC output from the rectifier, thus meaning there will be no apparent flicker. Even without the cap the change in light intensity is likely to be sufficiently rapid that most of us won't see it.