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  1. #1
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    Responsive all purpose bike light

    Hi, I'm a third year student at University currently carrying out a project designing a responsive bicycle light, mainly aimed at mountain biking, but that is also versatile for use on the road.
    The concept is to have a mode that uses a light dependent resistor to alter the headlight intensity depending on the light conditions. The original idea was generated from mountain biking in the day, to illuminate dark patches on the trail caused by tree shadows. However the other intention is from cycling on roads with street lights, to turning onto an unlit path or trail, without the need to toggle between modes and the current should change accordingly.


    Any feedback would be greatly appreciated, and is vital to ensure I design something useful!
    Thanks,
    Mark

  2. #2
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    USE sells a light that has a speed sensor to control output and there's another one that I can't remember that does something similar.

    I think a light sensitive light is an interesting idea, if you can manage hysteresis and response time. It's also worth thinking about the fact that at speed you need to see 20-30ft minimum ahead of where you are, which is the point at which ambient light is being measured. So if you're going from a light area (street light lets say) into a dark one your eyes and light will be adjusted to the street light and you won't see anything in the darker area. Similarly, if you're riding at night with others, there's the risk that their lights playing over yours will turn it down.

    I think we'd all be really keen to see what you come up with!

    (on another electronics note, I think wireless remotes for bar and helmet lights is something that would really benefit from a smart engineer's attention )

  3. #3
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    Since it's for uni perhaps you should use an arduino board or attiny chip with a gps module and light sensor. This would cover dimming with oncoming traffic or other riders on the road and the gps would act as a speed sensor to dim when slow, increase when fast.

  4. #4
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    Quote Originally Posted by mattthemuppet View Post
    USE sells a light that has a speed sensor to control output and there's another one that I can't remember that does something similar.

    I think a light sensitive light is an interesting idea, if you can manage hysteresis and response time. It's also worth thinking about the fact that at speed you need to see 20-30ft minimum ahead of where you are, which is the point at which ambient light is being measured. So if you're going from a light area (street light lets say) into a dark one your eyes and light will be adjusted to the street light and you won't see anything in the darker area. Similarly, if you're riding at night with others, there's the risk that their lights playing over yours will turn it down.

    I think we'd all be really keen to see what you come up with!

    (on another electronics note, I think wireless remotes for bar and helmet lights is something that would really benefit from a smart engineer's attention )
    Thank you very much for your comments, some really useful points. I agree with the response time issue, and am currently unsure as to how this would be solved. However, your point about the wireless remotes for bar and helmet is a really useful idea, and one that could potentially be incorporated to gopros etc. A light with a remote switch may be the way to go?

    Thank you both again for your comments, really useful stuff. I will keep updated!

  5. #5
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    Sounds like an interesting project. One observation that applies to mountain biking, I only ride on the road during the day, is that the hardest time to ride trails with lights is as it's getting dark. During dusk, your eyes are still adjusted to the ambient light and that's when your lights need to be at their brightest setting. Once it gets really dark, especially on a moonless night and when you're riding solo, you can typically get away with a much lower light settings. That's because your eyes dilate and a lesser amount of light goes a long way. So you may find that how you'd apply data from an ambient light sensor may be the inverse of what you initially may think.....at least for offroad trail riding.

    Riding in a group, with other riders of various brightness lights, is a whole differnt dynamic. It pretty much sucks to be in a group when everyone else is running lights at significantly higher light levels.

  6. #6
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    I'd second MtbMacguyver's point (nice to see you around BTW ) that dusk is a very difficult time for lights, even without others using lights in a group, and that you can get away with a lot less light than you think at night. I've been night riding with my commuter lights (3-400lm OTF) recently because their tint is so much nicer than my main lights and I haven't missed the higher output of the others except on fast downhills. Also helps that my riding buddy has lights with a similar output, so mine don't get drowned when he's behind me.

    I think a bar-helmet-gopro wireless remote would be awesome (you could leave off that last part for me), especially if you could get the receivers small enough. I think that would be enough of an engineering and electrical challenge as it is (ask Brad ).

  7. #7
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    I tried experimenting with dimming a bike light using an ambient light sensor (photo transistor / Mouser Part #: 755-RPM-075PTT86 ) similar to the type in most phones. I recall trying a photoresistor first but decided to try the phototransistor which I think was more sensitive to changes. The ALS was connected up to an arduino as a test platform using the ADC input, which had a LED bar graph so I could get an idea of how sensitive it was in various situations, and as I recall it seemed to work pretty well in general. However, I wanted to use it to detect headlights and dim the light, and found it was hit and miss for that - possibly a lens would have helped.

  8. #8
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    Mark, can you be more specific on the University?
    I remember there was a flashlight with this brightness feedback thing. There's also a flashlight with tilt dependent brightness
    CNC LED light housing for DIY projects

  9. #9
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    OK, here's my idea: make a stabilized light platform.
    When riding, the handlebar wiggles left and right. The stabilized light platform should dampen those vibrations. Also if you turn left or right the light can proactively rotate to light the turn.

    Similar to a gimbal, but only on 1 axis.
    CNC LED light housing for DIY projects

  10. #10
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    Thank you all for your help and suggestions, some really good ideas that massively helped my thought process. I am still going down the responsive light route, with a slightly developed concept after further research.

    The light will have a GPS module to track speed, and a Cadmium Sulfide ambient light sensor in order to respond to light changes. However, from the feedback I initially received there were some obvious limitations.

    The ambient light sensor will be situated in a lens that detect ambient light levels ahead of the bike, 20-30ft or so and coupled with the speed of travel, the lights can adjust intensity in time for that area. The speed will also be utilised to focus the beam, three LEDs will be present and as speed increases, the current will be fed more to the central LED and less to the side LEDs, creating a more focused beam.

    In order to validate the concept, I need some quantitative feedback, therefore I would really appreciate it if you could fill out my questionnaire: https://www.surveymonkey.com/s/Y6JBWZQ

    Thanks again for all your help, any further comments would be a great help.

    Cheers,
    Mark
    P.S I am at the University of Hull

  11. #11
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    Quote Originally Posted by MtbMacgyver View Post
    During dusk, your eyes are still adjusted to the ambient light and that's when your lights need to be at their brightest setting.
    agreed. right at dusk when I am thinking 'Hey I need light now' to go fast, I want -brightest- so shadows pop from the rocks and roots allowing me to judge things better. then later when totally dark out I don't need the same contrast

    maybe make it programmable (but simple!) with different curves
    Last edited by 127.0.0.1; 11-27-2013 at 05:47 AM.

  12. #12
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    Sounds like a cool project, there is another project going on where a light is being built with a motorized adjustable focus, seems like that would go well with this concept. I just had a thought about your project though. Two or more ambient light sensors could be used, and the outputs combined to get an approximation of the light situation. With several, they could even be looking in different directions. That way if the one sensor was pointed at a particularly dark spot it would not blast the light on - and alternatively if it hit a bright spot it may not dim too much.

  13. #13
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    Preventing the light from oscillating would need a bit of thought. Most lights use PWM to control their output levels. If you could ensure a unique frequency then a notch or bandpass filter would enable you to tell how much light was being produced by yours

    Sent from my Nexus 4 using Tapatalk 4

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