Prefocus LED headlight conversion

[AndyL]

Made a start on the headlight LED lamps to replace the normal 36/42 watt lamps that fit in the 7" reflectors on the Isetta.

Pictured is where I'm at so far. I had to sacrifice a filament a lamp by breaking away the glass to get some measurements of the filaments. Both filaments are about 21mm from the locating ring, with the dipped beam filament raised above and skewed to one side to dip the beam down and to the left.



The LED base is made from 2mm copper sheet, and I've silver soldered some copper pegs into that for the LED's to attach to. Copper is a very good heat conductor, these LED's are likely to poke out at least 2watts of heat per piece at the rate I wish to drive them, so good heatsinking is essential. The copper backing plate will be in turn bolted onto a larger finned aluminium heatsink, which will sit inside the Isetta's headlight pods.

I've staggered the pegs them to match the original positions of the tungsten filaments. The LED's are both made by Cree, the smaller unit for the dipped beam is an Xp-l emitter, the larger units are Xm-L. They both chuck out similar levels of light, but the Xm-L is cheaper and a bit easier to work with.

I have soldered the base of the LED for the dipped beam, I only plan to initially try a single LED pointing to the upper section of the reflector initially. The main beam will have two Xm-L Leds, one pointing down the other up to completely illuminate the reflector, but I've only soldered one in at present.

My chief concern at this stage is the sub optimal heatsinking. With the LED's mounted at the far end of the heatsink, this does affect the performance of the heatsinking, a term known as 'spreading resistance'.

Copper is about the best practical heat conductor, and I will also be running the LED's at well below their maximum output (these LED's are cable of about 1000 lumens per piece)- about 50% full power for the dipped beam, and about 30% for the main beam. It's going to be a case of suck it and see, they will undergo extensive testing before they go anywhere near a vehicle.

[plas man]

this sounds like a interesting project , lets hope it works - as no dout it will , but will the led's be able to supply the reflector with enough light ?
I'm just thinking about torch's where they employ lot of led's .
It would be a great saving on the Dynastarter .

Alan

[AndyL]

Should be more than sufficient light output. As I mentioned in my initial post, these LED's are capable of a genuine 1000 lumens at 10 watts.

At lower power the efficiency improves further.

Standard tungsten filament lamps push out about 10-12 lumens per watt, and that's when they're new and unblackened.

So at best from the standard lamps you'd get 432 lumens and 504 lumens for dipped and main beam. I should be able to get that kind of performance with the LED's running at about 4-5 watts total.

Almost ten times the efficiency.

[plas man]

I believe this or other like it was tried by a member of the Bond Owners Club , with out digging thro' past newsletters , if I recall he used a pre-focus LED bulb , but the LED was off centre for dip/main beam (for BPF) and the LED's throw the light every were , but straight ahead . 


Alan

[AndyL]

Completed the LED install, with two LED's for main beam, top and bottom.

Added some power connection wires, with power running to the LED's via strips of 0.5mm PCB board material. The layer of epoxy glass acts as an electrical insulator. The main frame acts as a return as well as a heatsink.

LED's were soft soldered onto the copper, and also secured with a dab of JB Weld epoxy, which helped keep them place during the soldering operation.



Beam spread appears to be equal to the filament lamps, power consumption, about 4.5 watts for dip, and 5 watts for main beam, with luminance levels that look equal to halogen lamps.

Dipped Beam



Main beam



Next job is to fit larger heatsink, and work out a method of clamping the unit into the reflector.

So far, so good.

[DaveMiller]

I believe this or other like it was tried by a member of the Bond Owners Club , with out digging thro' past newsletters , if I recall he used a pre-focus LED bulb , but the LED was off centre for dip/main beam (for BPF) and the LED's throw the light every were , but straight ahead . 

''Twas I who wrote that, Alan, and you remember it well.

The commercially-available LED 'headlamp' bulbs use many separate LEDs, which end up widely separated, leading to the poor beam definition.  What Alan's trying is individual, more powerful LEDs, which can better mimic the small filament in a traditional (incandescent) bulb.  I'm very interested to see the results.

[AndyL]

The LED's have only become bright enough in the last year or so for this to work well.

Prior to that, you would have had to series them up to get enough output, and that destroys the single point light source required to work well in a parabolic reflector.

With these and the other LED's, wattage should be reduced from about 94 watts under normal running conditions with dipped beams and no wiper motor, to about 18 watts. Neat.

[AndyL]

Not the best gauge, as I'm hand holding the reflector, so the beam moves between shots. however you can see the beam pattern is directional like a filament lamp, and luminence is good.

Filament dipped beam



LED dipped beam



Filament main beam



LED main beam

[AndyL]

Got my power supplies through. these are switch mode units good for about 3A (max). I'll be running them at about 1.5-2A so they shouldn't be too stressed. Cost about £1.80 each (posted) off ebay.

These are efficient power converters, dropping the voltage from the battery to the required 3 volts or so at about 90% efficiency.

You can adjust the voltage with the small multi turn pot soldered onto the board. If you want it locked you can either add a dab of glue on the pot, or replace the pot with a fixed value resistor.

[plas man]

looking good so far - is there a micro commercial side to the finished project ?


Alan (I must get the bottom Siba bush holder insulated before next season)

[AndyL]

I don't plan to make them available for sale, if that was what you're referring to. Quite happy to share information on suppliers and what to buy for those that want to take a crack at them themselves.

[richard]

I admit it I am a dinosaur ! my only real long distance experience of long distance night time micro driving was yonks ago . Back in the 90's i drove to Bob Parrys Shrewsbury Pub Night . January heavy frost , i remember the screen washer bottle being frozen solid , left after work and returned very late after the pub shut . 60 miles of very bendy country roads between here and there , pitch black country roads , hardly even a stretch of dual-carriageway , so 120 mile round trip and no problem at all . Are Heinkel/Trojans lights just that good or what ? Do you really need these or they just  the challenge of the project ? Seriously fascinating as it is .

[plas man]

I don't plan to make them available for sale, if that was what you're referring to. Quite happy to share information on suppliers and what to buy for those that want to take a crack at them themselves.

Thanks Andy (it was a hint  ) , not that i do much night driving now a days , it'll stick to my BPF 24/24w headlights . though it might be wise to make a spare set(s) for your self - just in case one blow's .


Alan

[AndyL]

The mod is designed to be backwards compatible e.g. you could just change them out for normal filament lamps.

Why am I doing this? It's not the challenge or the desire for better lighting. My Isetta is going to be fuel injected, and that means power needs to be found for the fuel pump and Lambda sensor. These combined draw about 40-60 watts.

So that's why I've gone to all this trouble. I guess the efi could be construed as a challenge- I wanted to learn more about modern fueling and ignition systems. I built up a Megasquirt (silly name I know, but a good product) engine management unit sometime ago, and also collected efi parts from a Peugeot Jetforce scooter, which included a throttle body (made by Bing!) injector and fuel pump.

My plan is to put the fuel pump in a swirl pot and have that gravity fed from the tank.

[Bob Purton]

Well that explains why you are going the LED lights route but that does beg the question, why the fuel injection? Are you not happy driving your vintage microcar as it was intended?