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Project Lights : Highpower LED Front and Rears

Discussion in 'Commuting' started by fisha, 30 Aug 2007.

  1. fisha

    fisha Well-Known Member

    I said in another thread that i would document the project of making some decently high-power LED lights , hopefully in time for the coming winter months.

    Its something that has been on my mind for at least a year now. I sometimes feel that bright lights from brand names are over priced for what they are and me being a typical tight fisted jock twat, i resent paying it.
    At the start of last winter i thought about doing it, but didn't. Now this year, I feel that the whole scene is reaching a decent level of maturity such that a project like this is feasable.

    ( Whether I make these lights for less than what i could buy off the shelf will remain to be seen. )

    The daft thing is that my commute in the future will likely become a thing of a the past should i change jobs, but none the less, i still want to do this project and complete it.

    So here goes. I'm starting right from the very very beginning here. I dont even have any of the fundamental parts delivered yet, but i have ordered them. I aim to document all the stages of what i go through. Hopefully this will allow people to gain the courage to do their own thing too.


    Principle Requirements

    My commute is typically about 12miles in each direction. There are 2 routes I can choose. The first is a busy A-road with a decent amount of traffic. Some sections are lit and in the dark, cars provide a decent amount of light to cycle by in addition to my own lights. Typical travel time is 40mins. The second is a single track road which is significantly quieter
    in terms of traffic, but is completely unlit ... think pitch black for miles. Travel time here is about 1 hour.

    In the darkest period of winter, both journeys could be in the dark, although in the mornings, it quickly lightens up to the point that lights are not needed to see by, but are better on to be seen by. Ideally i need at least 2hrs of good burn time.

    Factor #1: Front lights need to be good enough to see by for 2hrs or more in complete darkness at reasonable speeds

    Seconly, i want to essentially get home, unplug the battries, plug them into the mains and recharge them overnight ready for the next day.

    Factor #2: Decent ability to recharge the lights without much fuss.

    Lastly, I have more than one bike which I use on the commute, so i need to be able to swap the lights between bikes without fuss.

    Factor #3: Easily swappable onto any bike.

    So those are my goals. Lets go onto the theory.


    High Power LEDs : Current = Brightness


    OK, here goes. This is the point where I initially went :ohmy:xx(:sad::biggrin::biggrin:;):ohmy:xx( trying to get my head round it all in the early stages.

    Over the last few years, a new breed of LED light has become really very popular, i suppose they are nick named emitters, but they are made by all sorts of companies. The earliest big name was probably Luxeon. They come in 2 main forms. Emitter only, which is a tiny wee blob with little solder tabs sitcking out from it, or on a star shaped pcb ( which is the same blob, just soldered onto a heatsink style circuit board with much bigger solder tabs )

    These over the years have increased both in power and intensity. The current ones pump out 240 lumens of light. ( As I understand it, this is a bit more than a 10W halogen bulb ). The current best of breed seem to be Cree and Seoul emitters. I chose Seouls.

    Now ... whilst most people think in terms of Voltage, when it comes to LED emitters and their brightness, Current ( Amps ) is the primary factor to brightness from an LED.

    The LED do need voltage to get them to switch on in the first place ( typically approaching 4V ) but controlling the brightness comes from controlling the current. The more current you push through these things, the brighter it gets. The typical max current you pump through these emitters is about 1Amp, or 1000milliAmps, although its pretty common to run then at 700mA to preserve them a bit more and not work them so hard. So for these high power lights, its best to have a method of controlling the current.



    There are 2 main methods of controlling this current.

    1 type is where you provide more voltage than is needed. The controller then only pulls enough from the battery to generate the correct current rating. So if you have an LED at 4V inline with a controller needing 2V, then you need to supply more than 6V for the controller to function properly. The more LEDS, the more volts you need though. So for 2LEDS, i'd be looking at 10V supply or more.

    The second type is a boost style. This is where you supply less than the necessary amount of volts, but the controller generates a high voltage out of it in pulses which equates to the output equalling the correct current. The downside of this is that for generating 1000mA of current on the output, you may be pulling more than that from the battery . . 1100mA
    ...

     
  2. fisha

    fisha Well-Known Member

    Circuit types


    There are countless methods of powering LED's. I'll take you through 2 methods which I principally looked at, the first i chose not to follow. You'll see why once you read it, and you may find that in your case, the one I didn't chose may suit you better . . . it just varies.

    I originally decided that i was going to go down the route of using radio control car batteries. These are common, reaonsably cheap and offered about 7.2V each.

    First idea:
    My first idea was to build a light of 3 LED in series. I learned that each LED needed just under 4V of power and that the controller needed another couple of voltage ontop. You wire up the LEDs in series which was just under 12V needed, then add on the power of the controller doodah ( buckpuck ) so I was looking at needing 14V or more as a power source.

    If i were to pair 2 batteries up, then I could get 14.2V out of them ... this seemed like a good idea, and its a common method of doing it.

    My concern with this was that the RC batteries may drop their voltage quickly and i'd run out of power quickly. It also didn't really fit well with the idea of a rear light too where 3 LEDS would be overkill.

    Idea #2:

    On browsing the candle power ( links to come later ) forums i noticed a lot of people were talking about using the SHARK controller. On reading up about the shark controller, it seemed to suit my needs much more. The shark controller is a boost circuit setup.

    The blurb said that for it to work, you took your LED voltage ( 4V each ) and made sure that you could happily supply 1/2 of this value and call that your nominal voltage. The minimum voltage you needed to supply was 1/3 the LED voltage.

    This fitted in much better with a revision on the lights. If I made a twin light unit, then at roughly 4V each, powered by a 7.2V battery, then i would have plenty of scope and power for the circuit. That way i could make individual units of twins lights + battery. this would also mean a rear light could be made easily too. I was sold. This was the route I was to follow.

    ( Edit: I have since looked over the specs of the LED's i have bought and the battery source may need to change already! i'll explain later in a re-edit

    Whilst i was assuming 4V and had read that many LEDs were avtually 3.7V etc, i just looked at the fact sheet of the Seouls and they say they are 3.25V. This puts me under the 7.2V of the battery power source which is a big no-go for the controller board ... it'll blow the LEDs that way. I need to sort this out before I go any further . . . OOPS! ;)

    )


    The Enclosure

    You have to house everything, but also consider heat factors. LEDS pump out the heat and you have to have a way of taking that heat away from the LED base.

    Also, LED plus the lens are typically about 20mm in diameter. I was looking for an enclosure which would take 2 LEDs side by side and be able to dissipate the heat.

    So i chose this enclosure from maplin, specifically the 1455C801 version. This was nice and small at 23mm high, 54mm wide and 80mm long. Internally the space available is 20mm x 42mm when looking it face on. . . . perfect for placing two 20mm LEDS side by side.

    Also, the front face was easily removed by screws so i can replace the metal face with a clear one. The case is aluminium, so it'll draw away the heat as well. Its just what i was looking for.

    In terms of controls, i also got from maplin a basic toggle switch as an off/on as well as a 20k ohm pot which will be used to control the brightness.


    -----------------------

    So thats that at the moment. I have ordered the bits. You'll see my comment about the power issues . . . that has to be addressed, so i'll look into that at the moment and continue once i've sussed it.
     
  3. SimonGalgut

    SimonGalgut New Member

    Forget making them yourself. The hard part is not the electronics 'cos that's a doddle, but the casing and heatsinking. To get a good looking light that actually works requires lots of machining and anodising.

    As the P4's, lenses, puck and wiring is going to cost you about $60 plus carriage, why not buy a ready made light from www.nightlightning.co.nz This is a triple P4 with all the bits (excluding battery) for £99 direct (plus £10 carriage). Or, if you realy want, they will sell you any individual part to make your own.
     
  4. fisha

    fisha Well-Known Member

    i've added the enclosure bit above ...

    in terms of diy <> buy complete, its a project and a bit of fun really.

    cost wise, looking at a twin light very roughly it breaks down as

    2 LEDs + 2lens : £18
    Driver board : £ 11
    enclosure: £ 8
    odds n sods : £10

    very rough total: £ 40 ish for a dimmable twin light

    double that up and i'm at £80 for 2 independent units which i and adjust position and brighthess, and i'm still brighter and cheaper.

    Yes, i admit that there are other costs in there, but its for fun and its not significantly more expensive that off the shelf units.


    Heatwise, the LEDS will back onto a C-shape peice of extrusion which is 20mm in height. The top and bottom sections of the C will be bonded onto the top and bottom insides of the enclosure as it is also 20mm high internally. It should be an extremely tight and neat fit. Since the enclosure is extruded aluminium anyway and already clear anodised, i think its a suitable proposition ... or at least as suitable as a copper 28mm end cap
     
  5. xroads

    xroads New Member

  6. simoncc

    simoncc New Member

    Go to Wilkinsons and get their front LED light if they still do it. It's very bright and costs £2.99. So does the rear one.

    The rear one is one the web site, the front one isn't.

    http://www.wilkinsonplus.com/invt/0128491
     
  7. fisha

    fisha Well-Known Member

    I've not forgotten about this.

    Most of the parts have arrived and i've started fabricating the holders, but have encountered a problem with the lenses / optics i ordered. I had assumed that the optics for luxeons where mostly 20mm in diameter . . . the Fraen ones i ordered aren't . . . they are more like 25mm, so they dont fit by a mile. Sooo new optics on order.


    Regarding the power source issue listed in the first couple of comments of the thread, hopefully thats now sorted. I have ordered some voltage regulators so that i can generate a constant 5V to supply the LED driver board.

    This means that I can throw any voltage between 6.5V and 25V and the light unit will work as normal with no issues. My planned use of 7.2V RC car batteries actually measure 8.4V hot off the charger . . . so its perfect ( hopefully ) for powering the light units.

    Lastly for this post, i've decided i'm going to butcher a switch setup from an old set of lights. Decision for this was based on size of switches and space inside enclosure.


    So i've had to order a few more parts ... you live n learn.

    I'm taking pictures as i go along, but at this stage there is not much to see yet. Once these last bits arrive, i should be fully sorted to get stuck into the process of fully building the up.
     
  8. ...be dark soon - hurry up! :blush:
     
  9. Twenty Inch

    Twenty Inch New Member

    Location:
    Behind a desk
    Fisha - very very cool site. Well done. I'm inspired.
     
  10. KentS

    KentS New Member

    "The current ones pump out 240 lumens of light. ( As I understand it, this is a bit more than a 10W halogen bulb )"

    A good halogen bulb can put out some 20lumens/watt (the big ones used i cars or big lamps), but for the smaller ones usually used i bicycle lamps, like the Smart system 11 lumens/watt is more realistic. I've compared a 2*4.5W halogen (xenon) setup to my rebel LED light flashlight (200 lumen max, 112 lumens, 50lumens and 11 lumens optional) and at 200 lumens is really A LOT stronger than 9W of halogen, even the 112 lumen setting outshines 9W halogen. Another factor is the colour tempererature. You probably need more lumens of the yellow halogen light than of the very neutral white LED-light to see equally well.

    The unscientific measurements I've made at a very dark field at home shows that 200 lumens (with the beam pattern of my flashlight) give very good illumination up to 40m in front of you (every detail visible) and usable illumination up to 120m away.
     
  11. SimonGalgut

    SimonGalgut New Member

    I use lm2940 vRegs to use 7.4v li-ion battery packs to drive my 6v dynamo lights and also to drive my 5v Dinotte rear light. Work fine, but require a decent heatsink when you are drawing close to 1A.

    I don't know why you need vRegs for your main light, bcause a decent puck circuit will be happy with any input from vOut + 2.5v to about 20v. Obviously if you are trying to drive two SSC P4 with only 7.2v you are going to struggle. Have you seen the pucks with bike specific firmware from www.taskled.com
     
  12. fisha

    fisha Well-Known Member

    A puck circuit doesn't really suit the setup. I have 7.2V batteries and units which can only hold 2 LEDS within them. In order to use a puck circuit i would need to supply 10V or more ... so i would need to join up 2 batteries ogether and make use of the combined 14.2V .... not really something i wanted to do.

    I'm aiming to make 3 sets of lights. 2 front and 1 rear ... each essentially the same and each being driven off their own 7.2V battery. 7.2V wont drive a pair of LEDS when using a puck circuit ... so i'm using a boost circuit. A boost circuit driver needs a voltage supply below the forward voltage of the 2 LEDS ( i.e. less than 8V ). If you supply more than what the LED's use, then the circuit driver flips and blows the LEDs.

    The problem now is that even though the 7.2V batteries are marked as 7.2V, they actually measure 8.4V when fully charged .... this is above the voltage that the LED's use, so i have to regulate the supply to something lower.

    5V is a good option in this case. The boost driver works well when the supply is between 0.5x and 0.75x the voltage of the LED's. 5V falls bang in the middle of this.


    The regulator also has an overhead of 1.3V to work ... so this means i need to supply a voltage of 6.3V or greater to keep the whole setup running. With the battery packs actually 8.4V to begin with, that gives me a good amount of overhead to allow the battery to slowly drop down towards 6.3V as its being used.


    As for heatsinking the regulator ... thats under control too. All part of the design.
     
  13. andrew_s

    andrew_s Veteran

    Location:
    Gloucester


    P3D?
    If you go down to a caravan/camping shop, you can pick up a packet of tent rubbers (that go between the bottom of the fly and the pegs), and mount the flashlight on your handlebars in the same way as a Dinotte. It works very well.
     
  14. SimonGalgut

    SimonGalgut New Member

    Ouch ! That is so horribly inefficient - about 85% for the vReg and another 85% for the boost driver. If you want to stick to 7.2 / 8.4 volts, then your best bet would be to simply wire the LEDs in series across the battery with a resistor to limit current. Remember that the LEDs are not very voltage sensitive but are VERY current sensitive. So if you can stick a series resisitor in to limit the current to a max of 900 mA (to be on the safe side) you will be fine. This has the advantage of efficiency and looooong run times - the LEDs will just get dimmer as the voltage (and hence current) drops, whereas the boost driver will take more and more from the battery as the voltage drops and then suddenly cut out.

    Also bear in mind that the boost driver will be trying to draw a fair amount of current from your vReg in order to provide a constant 750mA (?) at 7.2v - certainly more than the LM2940 can provide and AFIAK most other low dropout vRegs.
     
  15. KentS

    KentS New Member

    Yep,
    I got the bike handle mount for it from Fenix-store. Wonderful light and under 100g including batteries - like music to a weightweenie :-)