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Traffic Lights

Discussion in 'LEDs and Optoelectronics' started by STM, Jul 12, 2011.

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  1. STM

    STM

    2
    0
    Jul 12, 2011
    Hi all

    need thoughts on how to control a single traffic light (not a pair) to go trough the motion of red amber green etc...it needs to stop on red for 5 secs approx and be green for about 30 secs. Or even have variable delay......

    Thoughts please. or if any one wants a project that is reasonable in expense i'll farm it out!

    Its for a charity that teach children from 8-12 years old traffic awareness in lincolnshire. So we are donating the traffic light head.

    We have the traffic lights and the bulbs are 12v 50W, in the sequence you will have red and amber on at the same time for a moment (remembering your highway code NOT...lol)

    Tel: 07508 014136

    Thanks

    Simon
     
  2. duke37

    duke37

    5,364
    771
    Jan 9, 2011
    This should be possible without too much trouble. I think it could be done with 2 chips, three power fets and a handful of diodes. The main problem will be the power supply, it will need to be 12V at 10A. It may be possible to find a simple battery charger to do this job. If this can be obtained, then the problem of mains safety is solved. A box would need to be made to house the electronics

    Oscillator 555 or 4093
    Johnson decade counter, one of ten output
    11 diodes to select output
    3 power fets to drive lights

    Using 5 sec pulses (total ten pulses) from counter you could get
    Red 10 sec
    Red and Amber 5 sec
    Green 30 sec
    Amber 5 sec
    I am not too far from Lincoln.
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    Yeah, I was thinking along the same lines. You have a red/amber phase do you? Interesting.
     
  4. STM

    STM

    2
    0
    Jul 12, 2011
    Duke - although I live in Lincoln - our business is based in Creswell on the edge of Derbyshire. Thanks for your input, what would you want to construct such a thing. I was also looking at a battery charger for the power supply. The unit can be housed inside an adjacent building so the wires to the traffic light head would be V.

    Although I am a a bit fresh between the ears when it comes to electronics, I only ever did basic electronics at school and in the motor trade, I found myself glued to this forum for about an hour yesterday. Fascinating.

    Thanks
     
  5. duke37

    duke37

    5,364
    771
    Jan 9, 2011
    I have an old 11A Absaar charger here and will look to see if the components will fit inside. It is a simple transformer/rectifier which is just what is wanted. It is quite battered but there are new ones advertised which may be the same circuit. You do not want one of the controlled type, some will not turn on if no battery is connected.
    I could stand the fiver for the parts if it is for charity. In return, you could perhaps help with getting the fridge to work in my Astra, I will be getting a Haynes manual tomorrow to find out the circuit. I might need the air conditioning if we have another day of summer!

    Steve
    Yes, we have a red and amber start phase, this enables us to get the turbos up to top speed and frighten the little old lady who is still crossing the road. There is no dual light on the stop sequence, either amber or red means stop.
     
  6. duke37

    duke37

    5,364
    771
    Jan 9, 2011
    Here is a proposed circuit, is this what you want and what is your timescale?
    The bits will fit inside the Absaar charger even though I have added some heat sink to keep a replacement rectifier cooler.
    What cable and connectors are you proposing?
     

    Attached Files:

  7. daddles

    daddles

    443
    3
    Jun 10, 2011
    Just a thought: how about replacing the (assumed incandescent) lights with some LEDs? Power consumption will go down quite a bit and yet might still be adequate.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    I'd contemplate wire-ORing the outputs with diodes (although with the number you need, it may be more compact to use the DIL package.

    Another fancy trick I've seen used is to use the outputs to alter the frequency of the oscillator. This can be used to make one transition much shorter than your normal oscillator frequency
     
  9. nepow

    nepow

    99
    1
    Jul 18, 2011
    Just a suggestion... Use high brightness clear lens LED's rather than filament lamps
    ( traffic lights are now using them). Also a pic micro controller is idealy suited here and can be programmed to provide the sequence...very simple and only a few components needed for the project.
     
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