Make your own LED lighting

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insanityideas
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Postby insanityideas » 1 Oct 2008, 11:10pm

When I made my own LED lights I got my actual LED's from http://www.dotlight.de For ease of construction you want to get the LED's that are mounted onto a hexagonal backing plate, unless you really really want to make a super small light and are good with fiddly breakable things.

As already mentioned you do need a lens (usually referred to as optics) this massively improves not only the light output but also the visibility of your light to other people. I didn't get my lenses from the above website, but they do sell the same lenses as I used, you buy them to match the light output pattern of the LED (typically lambertian).

My personal experimentation has found that the 5deg spot beam is great for viewing into the distance, and the oblong shaped 25x10deg is great for lighting up the full width of the road and kerb infront of you.

If you know nothing about electronics buy a pre-made LED driver, it needs to be constant current, and generally they are either 350ma or 700ma which equates to 1watt or 3watt LED. Its great if you can get a dimming one as then you can have different power levels for your LED's. You need to take account of the voltage drop across the driver when working out what battery pack to use. Generally a 10-12volt pack will power 2 LED's wired in series off of a controller. You can use use more than 2 LED's by wiring series pairs in parallel, just remember that you are halving the current (and brightness) each series set see's. Which can have benefits as LED's become less efficient the closer they get to full power. so 4 LED's consuming 700ma as two series pairs is brighter than 2 LED's consuming 700ma, even though power consumption is identical.

If you do know about electronics, you need to make a constant current driver, maplin sell a lovely device that does this with minimal extra components for about £1, and you can set it to whatever current you want.

In my setup I have used 2x3watt Red LED's for a rear light, with a wide angle, and a 180degree lens. powered off one regulator (800ma). and at the front 2x3watt white LED's powered off one regulator, with 3 power settings (350, 500, 1000ma). The system can run in flash mode or the front can be run steady mode with rear flashing. A 10 volt pack of AA batteries can run this. I ultimately intend to use 4x white LED's wired series parallel, so the power consumption is the same, but I have more efficiency (and so more light output), and a different beam pattern. Run time with rear flashing front steady low beam is about 6 hours. And low beam is ok to see by.

The most difficult part of the build was the prototyping of circuits, ultimately using the special regulator component from maplin solved this problem.

Making casings for the lights can also be a challenge, I go for the pre-made electronics boxes, and just drill holes in the right places, I used aluminum boxes so they act as heatsinks.

Most people comment on the brightness of this setup, and also the flashing pattern, as I used two 555 timer circuits to generate a strobing flash like that used on the new style police strobe lights (which also gives amazing battery life).

I had some prototyping costs (i.e. I broke some LED's - hence recommending those mounted on hexagonal base plates), but I recon component cost was only £30. Although I invested a serious amount of time, which is fine because I wanted something bespoke and its a hobby. There are no commercial lights that work in the same way mine do, however ones with a similar light output and battery life cost £300 (although they do use lithium-ion batteries, and have a battery gauge).

If anyone wants more guidance on a particular bit of what I have said (I have provided an overview rather than detail) then please ask. What I have tried todo is recommend a light configuration that I know works, as knowing what is bright enough, and what works off a specific voltage is the tricky bit.

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cranky
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Postby cranky » 1 Oct 2008, 11:18pm

insanityideas wrote:If you do know about electronics, you need to make a constant current driver, maplin sell a lovely device that does this with minimal extra components for about £1, and you can set it to whatever current you want.


L200C ?
Iain

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insanityideas
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Postby insanityideas » 1 Oct 2008, 11:40pm

cranky wrote:
insanityideas wrote:If you do know about electronics, you need to make a constant current driver, maplin sell a lovely device that does this with minimal extra components for about £1, and you can set it to whatever current you want.


L200C ?


Yes thats the one, its a 5 pin device, you can use it as constant voltage or constant current or both, making it useful in many roles (hence I bought all the ones they had in my local shop for future projects).

To make it constant current you need 2 ceramic capacitors, and a suitable value resistor (or a switch and different resistors). To get a low enough resistance value it will probably be necessary to connect several in parallel. The L200C datasheet (see google) has a circuit diagram.

I managed to get all the necessary components over the counter in maplin (although their web stock checker said they were out of stock, so best to ignore it).

You will need a small heatsink (bent bit of scrap metal, nothing special), slightly bigger if you need to drop lots of volts between supply and LED. I recommend purchasing a 7watt resistor (any resistance value) so that you can test the output current of the circuit without risking blowing up an LED.

For all of this a digital multimeter (with 10amp test mode) is essential. and some protoboard (plastic pegboard used for circuit prototyping) is highly recommended.

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EdinburghFixed
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Postby EdinburghFixed » 6 Oct 2008, 3:06pm

cranky wrote:The Constant Current supply you quote is a PWM 700mA supply. The Luxeons are 3.7V @ 700mA each. There is no option to run them at 2.95V (AFAIK). You would need a battery giving 8.4V (3.7+3.7+1) at the lowest part of the discharge slope in order to use that particular CC regulator.

Edit: I think you were looking at the second example on the driver circuit page. That's for two RED Luxeons @ 2.95V. I suppose you could always use two driver circuits, one per Luxeon. Also, I'm not at all sure those drivers are PWM. It says "PWM capability" so maybe it means they have an inhibit (switching) input allowing you to connect a modulator. There's no data sheet so I'm not sure.


Hopefully it's ok, as I'm making a back light to compliment my Ay-ups. I figured two red luxeons in serial at 2.95 plus a 1V drop for the driver is 6.9V and the battery is 7.4V. If I understand this correctly, they will run fine until the 0.5V drops away when they will switch off completely?

I guess I won't discover how this pans out until I do a test (ordered the bits last week). Apart from the battery it seems to be roughly the same system that the guys described on the linked discussion. I imagine I could sacrifice elegance and add a couple of 2700mAh NiMH AA's in serial to increase the voltage of my battery 'pack'?

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meic
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Postby meic » 6 Oct 2008, 3:49pm

Do you really want such bright back lights? Admitedly they may confuse car drivers into cutting their speed as they think it is brake or traffic lights ahead. Or am I over-estimating the brightness of these systems.
I have a single LED light running on 2AAA batteries which last 60hrs, cost less than £5 from Argos and is as bright or brighter than a car rear light.

I am all for abundant power at the other end of the bike but this seems like people who leave their rear fog lights on.
Yma o Hyd

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lauriematt
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Postby lauriematt » 6 Oct 2008, 7:08pm

Uncle Phil wrote:Take a look at this thread for some ideas.

As you'll see, I followed Fisha's instructions and built a front light. And it works, really well. And it's waterproof, and rugged.

I also have a B&M IQ Fly on another bike, and the light compares very favourably with that.


i like the look of those lights ALOT!!!

if i had the technical know-how thats wot id be making!
...ive just spent 30quid on a new light...would be great if i could make my own for the same price yet brighter
WHAT DOESNT KILL YOU .... CAN ONLY MAKE YOU STRONGER

insanityideas
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Postby insanityideas » 6 Oct 2008, 7:17pm

meic wrote:Do you really want such bright back lights? Admitedly they may confuse car drivers into cutting their speed as they think it is brake or traffic lights ahead. Or am I over-estimating the brightness of these systems.
I have a single LED light running on 2AAA batteries which last 60hrs, cost less than £5 from Argos and is as bright or brighter than a car rear light.

I am all for abundant power at the other end of the bike but this seems like people who leave their rear fog lights on.


Two Luxeon LED's running at 800ma are in visual appearance somewhere between the brightness of car rear lights and car brake lights. Using a suitable lens still gives them a somewhat smaller illuminated area than a car light though, so from a distance they don't appear as large (although they are visible).

As far as I am concerned when it comes to my safety on the bike I want as bright as I can get, I would have a different opinion with a car which is both significantly more visible due to its size, and more capable of generating glare. I also have my lights on flash to make them even more annoying.

So far I have noticed that cars give me more room when overtaking, and tend to hang back further, so mission accomplished!! I absolutely garantee your Argos LED light isn't as powerful as a car rear light. The thing to remember is it will have a very narrow field of view in which it is at full brightness, whereas my rear light (and that of cars) spread a near 180degree field of view.

EdinburghFixed wrote:Hopefully it's ok, as I'm making a back light to compliment my Ay-ups. I figured two red luxeons in serial at 2.95 plus a 1V drop for the driver is 6.9V and the battery is 7.4V. If I understand this correctly, they will run fine until the 0.5V drops away when they will switch off completely?

I guess I won't discover how this pans out until I do a test (ordered the bits last week). Apart from the battery it seems to be roughly the same system that the guys described on the linked discussion. I imagine I could sacrifice elegance and add a couple of 2700mAh NiMH AA's in serial to increase the voltage of my battery 'pack'?


You should be fine just connecting up the regulator. I would strongly not recommend connecting extra batteries in series, as it won't work as expected and could damage both battery packs. You probably have a correctly sized battery for this application, depending on how much the voltage sags when the battery is loaded (i.e. lights on).

As the battery voltage drops the LED brightness will deminish, the regulator controls the current going through the LED by varying it's output voltage, so when it has a low input voltage it just stops varying the output (although it will still cause the same voltage drop).

Most regulators will allow you to connect the LED's in parallel, this would have the effect of doubling the current and halving the output voltage to get the same effect (so you would need a 1400ma regulator), it would also be very inefficient, but it would entirely prevent dimming.

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meic
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Postby meic » 6 Oct 2008, 9:18pm

I see your point about the light being directional, my observations were from half a mile away on a straight road directly behind the bikes and cars which were overtaking them.
Yma o Hyd

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Wobbly John
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Postby Wobbly John » 6 Oct 2008, 10:08pm

I made a super small 3W luxeon LED front light out of a cheap torch last year. I run it from a hub dynamo with just a rectifier in the wire. It flashes quicker as you build up speed and gives almost constant light over 15 MPH. I like the flashing as it gives extra astonishing value.

I did a webpage when I started the project, here

It has been running almost a year, and I used it during the Dunwich Dynamo. It is much brighter than normal battery lights and compares well with some of the comercial units.

This year Tescos have the even brighter, 3W Cree torches at £10. If you can't do the machining, just leave the battery compartment on and connect up a cable to the dynamo.

insanityideas
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Postby insanityideas » 7 Oct 2008, 9:43am

Wobbly John wrote:I did a webpage when I started the project, here

This year Tescos have the even brighter, 3W Cree torches at £10. If you can't do the machining, just leave the battery compartment on and connect up a cable to the dynamo.


Cool, thanks for the website.... and the Tesco info... torches like that used to cost a fortune (although its still 90% markup for Tesco).

Your end "bodge" looks really really professional... you should be able to run a pair of them off a 6w hub dynamo.

Anyone looking for a bodgy handlebar mounting could try out a reflector bracket, if you don't mind it being permanently bolted to the bike.

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EdinburghFixed
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Postby EdinburghFixed » 7 Oct 2008, 2:34pm

insanityideas wrote:You should be fine just connecting up the regulator. I would strongly not recommend connecting extra batteries in series, as it won't work as expected and could damage both battery packs. You probably have a correctly sized battery for this application, depending on how much the voltage sags when the battery is loaded (i.e. lights on).

As the battery voltage drops the LED brightness will deminish, the regulator controls the current going through the LED by varying it's output voltage, so when it has a low input voltage it just stops varying the output (although it will still cause the same voltage drop).

Most regulators will allow you to connect the LED's in parallel, this would have the effect of doubling the current and halving the output voltage to get the same effect (so you would need a 1400ma regulator), it would also be very inefficient, but it would entirely prevent dimming.


Thanks, that's good to know.

I've got hold of all the bits and pieces now apart from the regulator (a 700mA one is on order, if it doesn't work out I'll look into other options).

As far as brightness goes, perhaps they will be over the top. However I've got elliptical lenses (6° / 25°) to start off with and am hoping that will allow me to aim accurately.

Tthe original idea was to use it largely to light the ground and create a 'danger zone' but the beauty is, I can just swap one or both lenses around until I like what I get.

insanityideas - is your 180° lens in the 20mm 'format'? Do you have a link?

insanityideas
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Postby insanityideas » 7 Oct 2008, 6:52pm

EdinburghFixed wrote:insanityideas - is your 180° lens in the 20mm 'format'? Do you have a link?


The 6/20mm lens is actually very versatile, it is ideal for on road use (and off road) as it basically lights up the full width of the road, but the beam is narrow enough vertically to get decent throw into the distance. You can match it up with a 5 degree spot lens to view further into the distance.

Both of these (and indeed others) are visible from angles outside of their direct beam, in a way that is much better than traditional LED's so you already get some sense of 180 degree visibility. same as you would with the lenses on car headlights.

On the rear light I also used a 180 degree lens that produces a very narrow (vertically) beam, that is very wide. So it appears as bright as the more conventional lens but is visible at a wider angle, it does require more careful aiming. Here is the link: http://www.l2optics.com/flare.aspx

l2 optics make most of the acrylic lenses that you can buy from various places, the round lenses are much easier to use with the lens holder that they also sell. You can buy direct from them, although I had a crappy experience when I did, the first delivery got lost, the replacement did arrive, but they are not set up for customer service to low volume sales, and they recommended that I buy direct from RS components next time!! I only went direct because RS was sold out. Don't let that put you off, just be aware that internet sales isn't their primary business.

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lauriematt
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Postby lauriematt » 7 Oct 2008, 9:11pm

EdinburghFixed wrote:
Thanks, that's good to know.

I've got hold of all the bits and pieces now apart from the regulator (a 700mA one is on order, if it doesn't work out I'll look into other options).

As far as brightness goes, perhaps they will be over the top. However I've got elliptical lenses (6° / 25°) to start off with and am hoping that will allow me to aim accurately.

Tthe original idea was to use it largely to light the ground and create a 'danger zone' but the beauty is, I can just swap one or both lenses around until I like what I get.

insanityideas - is your 180° lens in the 20mm 'format'? Do you have a link?



any chance you could take a few pics of the process????

am going to have a crack at it over the next few weeks...but would be interested to see how you get on making yours
WHAT DOESNT KILL YOU .... CAN ONLY MAKE YOU STRONGER

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EdinburghFixed
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Postby EdinburghFixed » 7 Oct 2008, 11:23pm

Will do. I don't expect it will be the most craftsmanlike effort - but if I get it to work, I'll be happy enough! :D

Unfortunately that flare lens is too large to fit my light case (25mm a side) but I might order a couple up anyway, just to see. I can always get a bigger case! :wink:

Graham S

Postby Graham S » 8 Oct 2008, 12:08am

Wobbly John,

Great page, that is exactly what I am doing but with the new tesco 3W Cree torches as you will see in the "lumicycle anyone?" thread. You beat me too it.

The AA version is built slightly differently to the C cell version and you can just remove the central section of the torch and glue the back and front together with epoxy very neatly. Drill a hole and you are done pretty much.

Graham