Automatic Bike Light (with light sensor and motion sensor)

Discussion in 'The Projects Forum' started by keabler, Apr 17, 2013.

  1. keabler

    Thread Starter New Member

    Apr 17, 2013
    8
    0
    Hi all,

    My project idea:
    I want to build an automatic bike light that detects when it is dark and when I am moving (so I don't have to turn it on or off).

    My Background:
    I am in my last semester of physics so I have some experience in building circuits and the general theory behind how many of the electronic components in a circuit work; however, I don't have much experience in designing circuits.


    Where I'm at:
    I know that I need an accelerometer, photo-diode, LED's, and a battery. What I'm unsure about is how I can design a circuit that will compare the output from the accelerometer and photo-diode to control whether or not the LED is on or off.
    - Do I need to use a transistor circuit, or is this more easy to accomplish with a microcontroller?
    - How would I design a delay into the circuit (so that the light wouldn't turn off when I'm stopped at a stop light or when a car passes me)?


    Thanks everyone and I apologize for my noobness, but building electronic circuits is something I would like to get into. I've even built an audio tube amplifier for my final project in electronics lab, but I didn't design that circuit.
     
  2. poopscoop

    Member

    Dec 12, 2012
    139
    16
    Omit the accelerometer, use a switch or pressure sensor in the seat instead. Infinitely simpler. Incorporate an RC time constant to control shutdown. This will solve the passing headlights and stand-up problem in one fell swoop.
     
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  3. keabler

    Thread Starter New Member

    Apr 17, 2013
    8
    0
    Thanks, I wanted to house every thing for this build inside the stem of my bike so that the only visible modifications form the outside would be the 2 LED's that would shine through a hole in the handle bars and maybe a charging port at the bottom of my stem (out of sight, I have a pretty "nice" bike and want to keep my light modifications as incognito as possible). If I used a pressure pad on the seat I would have to figure out a way to conceal cables from my seat to my stem which is doable but somewhat involved.

    If I put a switch on my bike I wouldn't need the light sensor or accelerometer since I could just turn the light on and off when I needed it.

    Also, I do have some experience with microcontollers and accelerometers. I've programmed a PID controller for a segway project I worked on for fun. However, I don't have much experience with electronics and am open to suggestions. Maybe a switch operated system would be best.
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,392
    1,606
    If you are putting in a charger then you have an effective sensor for "in use:" the generator output voltage itself.

    I'm a micro controller guy, and this screams USE A MICRO to me. While it is possible to do with discrete parts, it will be a cleaner design with a micro. With a micro you should not need any switches at all.

    Plus you can add lots of other tricks for virtually nothing.
     
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  5. keabler

    Thread Starter New Member

    Apr 17, 2013
    8
    0
    Thanks, I'm just starting to think about this project (all though I have purchased some 3 watt LED's and an appropriate rechargeable lithium battery so I can have a switch operated system while I work on the automatic system).

    Do you have any suggestions for a microcontroller that would work well for this? I've used an arduino before, but I don't think I need any thing that "elaborate" for this project.
     
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