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Rear LED lights - wide angle or narrow beam

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

  1. fisha

    fisha Well-Known Member

    In for a penny, in for a pound.

    I'm going to make a set of highpower front LED lights. 2 units of 2 LEDs ... max output about 800 to 1000lumens ;)

    I thought whilst i'm at it, why dont I make a rear light too. A unit with a pair of red 3W Luxeon LEDs. About 200 lumens on the spec sheets. But i can choose how wide or narrow to make the rear beam.

    So which would you choose if you had the choice? A narrow beam with a really intense sweet spot or a generally wide spread out beam?
     
  2. Well, I guess a rear light is solely to be seen with, different to a front light where it might be to be seen or to see yourself.

    A narrow beam would be visible from miles behind you - but only if directly behind you.
    Which would be great if you had angled the light correctly and were riding along a dead-straight road, any car catching you would see the light miles back.

    But the fancier commercially-sold LED lights have lots of LED's, arranged pointing in an arc from the left and right as well as backwards, sometimes some pointing gently upwards and some down.

    This has to be better to be visible from as many angles behind as you can manage.

    Personally, when I'm cycling in the dark it's mainly on poorly-lit main roads or unlit country lanes. Bikes aren't as common as on inner-city streets.

    So I run a flashing 5-LED thing, plus a bigger, bright steady single LED.
    The rationale being that the flashing is noticeable and says 'bike' to someone coming up behind me, the steady light allows them to better judge my speed and distance than a flasher does.
     
  3. John Ponting

    John Ponting Über Member

    Location:
    Herts
    I want as many people as possible to see me and have the chance to avoid me. A narow beam will only be seen from due astern.

    just my opinion.
     
  4. OP
    OP
    fisha

    fisha Well-Known Member

    Well, I've placed the order for the LEDs and lenses. For the rear, i chose a medium pattern beam which should be about 30° spread pattern which is decently wide.

    Its all going into a small aluminium enclosure, so i may suppliment the main LEDS with a couple of small normal ones which will throw sideways light. That would be simple enough to do as well with stuff i have lying around.
     
  5. Mister Paul

    Mister Paul Honky

    Location:
    North Somerset
    May I ask where you are buying all this from?
     
  6. Twenty Inch

    Twenty Inch New Member

    Location:
    Behind a desk

    That's my thinking and practise too. When I'm in a car on a dark country road, it's very apparent that one LED light will tell you that there's a bike ahead, but without reflectors, another light or some other reference point, it's very difficult to judge speed, position etc.
     
  7. OP
    OP
    fisha

    fisha Well-Known Member

    Paul, various places . . no single source, plus a good bit of head scratching over the last year toslowly get my head around it all.

    www.Maplin.co.uk
    Aluminum enclosure with screw on ends
    Switch
    Rotary 20k ohm resistor for dimming
    funky silver control knob for dimmer

    http://www.dotlight.de/shop/
    LEDS 4x Seoul P4s + 2 LuxIII Reds
    Optics 4x Narrow Beam + 2 Medium beam ( Fraen )

    http://theledguy.chainreactionweb.com/index.php?cPath=48
    The SHARK circuit driver.

    Other bits n bobs I already have, such as 7.2V NiMH radio control car batteries and chargers etc etc which i'll use as test stuff, and then i'll buy more of what works best.

    I'll start a different thread about the build shortly, describing my choices.
     
  8. Mister Paul

    Mister Paul Honky

    Location:
    North Somerset
    Thanks for that.

    Do keep us updated.

    You never know, we could end up manufacturing CycleChat lights.
     
  9. bonj2

    bonj2 Guest

    Last year I bought all the parts for making a super-power front light, but have never got round to putting them together. Partly due to not being able to figure out how to make a good enough handlebar attachment to attach to the case, and partly due to always having something better to spend money on than a bucketload of AA batteries. But I might revive my efforts if i've got a bit of money left over after my van mods...

    edit: if you Paul or anyone else is interested in the shops where you can get 'ingredients' for lights from, then iirc i got them off www.farnellinone.co.uk and www.led-tech.de
     
  10. squeaker

    squeaker New Member

    Location:
    Steyning
    Rear lights

    Both! A large rear steady light with a broad beam - looks 'big' from the rear - and a narrow bright flasher to grab their attention from some distance away.
     
  11. frog

    frog Guest

    Two LEDs, can't you have one of each? If you're throwing out 2 x 3 watt (twice what the Dinotte tail light produces) 6 W will either get you pulled over by Mr Plod or 767's trying to land behind you on the straight bits home. :ohmy: