Miscellaneous LED Questions

I only signed up to steal knowledge from this forum, so forgive me for being parasitic. My questions relate to LEDs but they are for automotive purposes not torch purposes. Unfortunately there isn't really another forum around with so much knowledge about LEDs and light sources etc. I'd appreciate your wisdom guys!

I am making some custom indicators (turn signal for the US folks) for my bike. They will be housed and hermetically sealed in a brass fitting similar to those used in plumping/fluid/air transfer. I have found this LED which looks very f* bright which I want http://www.superbrightleds.com/more...4-led-bulb-1-x-1-watt-smd-led-wedge-base/205/ . I

Q1. Will there be a problem with heat? It will be blinking at a normal indicator (turn signal) rate at the supplied 12v. There may be a very slim air pocket around the silver body. How much do these things heat up?
Q2. What is the best way to weatherproof/seal the LED face without compromising beam spread? I was thinking clear polyester resin, perspex disc drilled out with a hole saw, or premade glass lens of say 10mm diameter, but I haven't been able to find these anywhere <Q5?.
Q3. Is there a better purpose LED for this. It needs to be amber, wide angle, very f* bright, diameter of ~10mm or less, and doesn't require any circuitry to be complete ie just + - terminals soldiered.

Well, we have a policy on this forum of following laws. So let's get this one out of the way: Is this for a bicycle, a scooter, or a motorbike? There are safety laws regulating safety lighting (Headlight, turn signal, brake light, etc) on most motorized vehicles in most countries.

The reason not to DIY is a few things that could injure or kill you or others.

1. Build quality. It's easy to DIY a light. It's hard to make it:

Rainproof. Waterproof. Vibrationproof. Electrical-spike-proof (80 volt rated stuff dies with alternator-supplied power). Temperature-proof. Corrosion-proof. Rockproof. UV-proof. Maybe you're better at DIY than I am, though. High output is NOT the key factor in safety lighting. The brightest light in an advanced car puts about 500 lumens on the road. My thumb-sized pocket light beats that by 20%, but it'd make a very bad driving beam.

2. Light distribution. It's actually tough to make a qualified lighting system, and simply un-affordable to self-certify your light as an OEM must.

On- and off-axis min/max candela. Non-interference with other safety lighting. Correct color, location, and such. Optics made of certified materials are very expensive to make, and modifying the design as you iterate is more expensive. These things help ensure that your light doesn't blind people but is still visible.

3. Liability. Suppose something bad happens and your DIY safety lighting can be at all blamed? Shark-lawyers will be glad to discuss the pitfalls I'm telling you about. Right or wrong, that's a big can of worms. And modifying safety equipment on a vehicle can injure or kill people. That's a lot of responsibility to take into your own hands.

So: Motorbike or bicycle?

It's a motorbike but it's a show bike which doesn't see the road. These ideas are conceptual at the moment and won't see any road use. That said, I'm from Australia and there are laws here of course which require turn signals to be x-distance apart, and for the lens to be e-marked. I don't want to get too deep into the safety debate but I want to keep the discussions sensible. I am not asking to modify an essential safety component of the vehicle, I'm not asking for a DIY-headlight or brake light, or chopping up suspension or compromising the brakes. The turn signals are not a critical component. I'm sure we could come up with some ridiculous scenario where a turn signal could cause an accident, but like I said we should keep this sensible and real-world.

Now you have said it is difficult to make them robust. Waterproofing and vibration are easy fixes. Temperature proof from the sun or the LED? Corrosion, rock, and UV aren't issues as the brass housing can be ran over by a truck without bending, it is water tight, and the acrylic lens are UV resistant and has very little direct sun exposure anyway.

There are many many LED indicators coming out of China which work fine but are made quite crudely. I don't feel they compromise safety at all, perhaps only style if anything. I don't think this should be a complicated task, the LED I linked is a direct replacement and is intended for automotive use with a bit of further DIY customisation on a minor level. I'm here to find out what that is.

With respect I think your fears about the liability are misplaced. I am not modifying an essential safety component. For eg motorbikes pre-1976(?) aren't required to have any indicators at all, so the law recognises that it is not as absolutely essential safety component enough to warrant their mandatory retrofitting.

My original questions remain,
-does anyone know how hot these LEDs can get
-and at 12v, is the rated lumens too bright or is there something more suited for the job?

Cheers.

Well, if it's a show bike then we'll go on.

Most LEDs want about 2.5 to 3.5v. You'll need a driver of some kind, but those aren't so hard to come by. A common rule of thumb is that a moving bicycle needs about 2 square centimeters of exposed heatsink surface per watt of LED, or about five times that when not moving.

Putting power into an LED requires it to release energy (Something like 2/3ds of the electrical energy becomes heat, much better than 90% for a halogen requiring ten times the power). In theory it will increase in temperature until it reaches equilibrium. In practice, LEDs usually fail at over 150C, and suffer over 100C. So you may be best served doing testbed work.

I am on limited internet now, so here are some general things:

Buy LEDs on 'stars' if you can afford the space. They're much easier to handle this way.
Use LED drivers. If the input voltage is right, and the output current is right for the LED, you're set.
Most LEDs (Lambertian, not batwing) have a wide viewing angle.
I suggest using thermal grease for mockups, and thermal epoxy for final build.
You'll want a multimeter and to know how to use it.

I am confused a little. I understand some LEDs need drivers for torches etc, but isn't the product I linked originally, as well as this http://www.superbrightleds.com/moreinfo/miniature-wedge-base/194-led-bulb-1-smd-led-wedge-base/204/ a product which does not require a driver or it is inbuilt already? These are being marketed as drop-in replacements for bulbs, thus I plan to use these in place of indicator bulbs and just replace the indicator relay to one which is electronic and not mechanical (otherwise the blinking rate doubles/triples). Can't I just take that LED smd wedge bulb and hook up 12v terminals (it says operating voltage is 9-14v) ?

My other requirement is that it ideally be under 13mm in total diameter which rules out the starfish LEDs correct I believe.

Thanks for the thermal epoxy tip didn't even know it existed.

Usually 1W isn't very bright. But since this is a show bike you don't need much. And the less power it consumes, the less heat it builds up, the less heat the builds up, the smaller the heat sink needs to be.

Most leds dont require anything more than positive and negative so I don't follow that question. If you're looking for a drop in bulb to be super bright than best of luck.

If you want to look at lens then go to flashlight lens dot com and look at UCL lens, they're practically invisible.

I see. That's meant to be a drop-in replacement for certain types of car/motorcycle bulbs. It will have a different (And unsafe-for-road-use) beam pattern than a real filament bulb, but it may be brighter.

Normally LEDs only use less power for the same output as a filament. They can do this because they emit 33% light instead of 5-10%, so the bulb can use much less power (3 to 1 or better). For example, I can get similar output, and much greater runtime, by sticking a 5mm LED into the socket of an incandescent mini mag lite. To get an LED brighter than a filament requires heatsinks, higher current, and special electronics (drivers) to keep the LED near its rated current. These parts are expensive and don't work well inside a housing.

So: The bulb will work, but I don't know if it'll be bright enough to write home about. I think the signal bulb on a car turn signal is 3x the output (And 5x the power use) of this.

In the end I just bought a sample. Apparently they run on 12v or work within that range. I was worried that the original one I linked would be blindingly bright. I also wanted to stay away from having to use drivers or circuitry to run them so these should just be plug n play. I found a place that does laser-cutting acrylic, smallest circle they can cut in 3mm (amazing!!) and the sun shouldn't be a problem. Only problem with acrylic is that it's totally flat and due to the design of the housing, a lot of the light angle will be narrowed.




Does anyone know of any very small acrylic/poly lens that would change the beam to more of a flood instead of spotlight? probably about 10mm widest ... Kinda similar to the one found in this product http://japan.webike.net/products/9397253.html

Ok so I bought one of these 1 watt LEDs http://www.superbrightleds.com/morei...edge-base/205/

I've just tested it and hooked it up to a 12v battery (Range 10-30v DC) and it's nice and bright and perfect for what I want. The only issue I think is heat management. I left it on for about 30 seconds and the temp hit about 43 degrees on my shitty infrared thermometer.
I'm planning to find a very snug fitting brass tubular piece and slotting it in, then using a thermal adhesive or something similar so that the heat can dissipate into the brass.

1. Considering the stated operating temperature is 85c max, how could I best keep this thing cool, keeping in mind the summer sun may heat the brass housing itself up more than the actual LED will.
-Should I leave an air pocket with air vents beneath? or
-Thermal glue it to the housing and use that as a massive heatsink?
At most, they will only really be flashing for a few minutes rather than left constantly on at length.

2. How can I safely test how much heat it can handle/how hot it will get after flashing for 5 minutes? Do I just turn it on and touch it every minute? I'm scared it may blow out. What's the safe temp limit before I should turn it off?

Be careful how you measure LED output. The photons can heat the sensor in your non-contact thermometer, giving hilariously high values. You have to check a non-lit area, or turn off the unit just before measuring.

Thermal glue isn't really very thermally conductive. It's about as good as toothpaste, and really only helps for filling narrow gaps. The failure mode is most likely to be gradual dimming, which isn't a big problem in a show car. Vents are likely to allow rain in, aren't they? I say, run it in a warm place in the enclosed fixture and see what happens. That'll tell you if you need to get clever with thermal management.

Well I tried the toothpaste like you said and it made a complete mess of everything.


Just kidding......


I measured from the side of the LED on the aluminum casing. I can only use passive cooling here. Is it better to leave an air pocket around the light with holes for ventilation (holes will be on underside) or use a very thin layer of thermal glue to dissipate heat into brass housing?

I actually put it on flash mode yesterday for 30 seconds and it obviously produced less heat than constantly on, which is good. Does flashing an LED reduce its life rating, as it would with a filament bulb?