LED bulbs

[plas man]

question to all , do LED's stand up to indicator use with constant flashing ?
Reason I ask is the local £ world as some 12 led , 12 volt bulbs 50mm round  , the type you put into the ceiling . and with a bit of modification it would fit a Lucas light unit , or use as running lights . 

[marcus]

Have just my band mate, an electrician, and he says LEDs are NOT good for repeated flashes. Shame!

[Barry]

Is that why they don't use them for flashing Christmas decorations?

[marcus]

I reckon I have seen plenty of flashing LED Christmas lights, but have no idea how long they last! Perhaps they have a particular type of LED, or perhaps some extra components or circuitry. I do have some flashing LEDs in my bass guitar, but probably not bright enough for indicators.

[Peel replica, Steve Fisk]

Funny ive been playing around with LEDs a lot resently , reason is to bring the power drain down so the charging of the battery is better , I've got a relay that works really well with low led current, I can make you some circuit boards up that you screw straight in to your lights if you like

[AndyL]

I'd take what that electrician said about flashing led's being no good with a very large pinch of salt. They work perfectly well being strobed.

What you can't do is use them in standard indicator circuits with a bi metallic electro mechanical flasher. This is owing to low current the LED's draw from the supply not permitting the unit to work as it should. So you either need to use parallel resistors, which nixes the advantage of the low current draw, or fit an electronic flasher.

[marcus]

That's probably what Sparky was on about and what I hinted at... a bit more circuitry!

[DaveMiller]

There's no need to go modifying household units: you can now buy, quite cheaply, many kinds of automotive LED bulbs which will fit straight into the sockets on the car, and put up with vibration etc.

To save on current, I've changed over most* bulbs on both my Bonds, some years ago, and have not yet had to replace a bulb.  The reduction in current required has been dramatic.

*The headlamps I've not changed for LED, as I could find only bulbs with multiple LEDs in a large cluster - not able to replicate the "point source" of the filament, and therefore giving a hopelessly unfocussed spread, rather than a beam.
One Bond owner, though, recently showed me some single-LED headlamp units which he'd fitted to his 6V car.  One upward-facing LED comes on for "dip" (the beam heading downward after being reflected), while a second, downward-facing, LED also comes on for "main".  The lights looked bright, but I'm waiting to see how well they work at night.

LEDs make good indicators, as they come on (and go off) very much faster than an incandescent filament heats up and cools down. This gives a starker, more noticeable flash. (In brake lights, the quarter-second difference is worth 11 feet at 30 mph - perhaps the difference between the following car pulling up behind you, or inside your boot!) However, because the LEDs take so much less current, it's not enough to trigger the correct flashing rhythm in traditional flasher untis.  If you move over to LED flashers, you also need to change the flasher unit for an LED-compatible one.

Addendum:  Oops, I see that AndyL made that last point while I was typing!

[AndyL]

To give you some idea of longevity of LED's. We fit them in railway signals, they've been in over ten years now, and they're on 24/7 in fairly harsh conditions. Relatively few failures and no replacements. When we still used filament lamps, relamping was common, even with 12 weekly maintenance intervals.

In a car, you should expect them to last for a lifetime and possibly beyond.

LED's are about five to seven times more efficient than filament lamps, so you will save some juice.

[AndyL]

With regards to headlamp LED units. There are a variety on the market now, and as they're mainly from China, they're not terribly expensive. Couple of points to bear in mind, the output of these units tends to be fairly hot, so the wattage saving over incandescents isn't huge, if that is what you're after. The output is obviously much better however.

Another point is focusing, the units I've seen tend to use large LED chips, so I'm wondering if that is likely to give you more dazzle. At best that could give you an MOT failure, and at worst get your collar felt.

[eaurouge]

AndyL, Not sure with what you say about them running Hot, incandescents tend to run very hot too! I have found them to be slightly cooler when I have used them!

If you think about it nearly all high end cars these days have LED, and they are drifting down the prices as these things do. They have lots of subtle benefits, like they can be lots smaller than an incandescent bulb, so you can place them into things like trafficators to give that subtle bit of extra change that the person in a modern car will see your intentions!

My regular car has been converted over, and several classics I have had recently have been converted as lighting issues are found, I  find them much more stable.

[marcus]

I find it ironic that LED lighting was at first exclusively London buses, then on large expensive cars, all with plenty of space for their powerful alternators!

It is only recently that LEDs are moving down to cheap small cars, where large alternators are more of a problem, and now even to classics, the very cars whose dynamos are best suited to the lower power demand of LEDs!

[AndyL]

They're more expensive than incandescents, at least the up front purchase is. Gradually they're levelling out, and eventually they will become cheaper I think.

When I say they run 'hot' I mean they are powerful LED's, they tend to be about 20-35 watt draw, not far away from the low powered incandescents used in micro cars. This is why I went down the route of growing my own, I found 4-6 watts was sufficient to obtain the same level of light output as the original 36-42 watt BPF lamps. However obtained a 64-72 watt reduction in power required. With the rest of the lamps adapted to LED, the overall saving was about 100 watts.

The dynastart will be working at less than 25% of its rated capacity.

[marcus]

Always nice to have plenty of "spare" capacity because you never know when you might be grateful of it, especially in classics!

[AndyL]

In my case I was aiming to free up capacity for electronic fuel injection.

This means a pump and wideband lambda sensor. the two combined can draw up to about 45 watts, although that reduces to about half that amount once the lambda sensor has warmed up (they have a built in heater which draws most of the current).

I figured with a standard system a flat battery and night running would almost certainly drain the battery, so I looked at LED's.