Traffic Light Circuit Problem...

Discussion in 'The Projects Forum' started by the kidson, Aug 25, 2011.

  1. the kidson

    Thread Starter Member

    May 15, 2011
    32
    0
    hello all...i made a traffic light circuit...the circuit works fine..well kinda...the first time i ran the circuit it worked...with the only problem being a prolonged yellow light...the second time it cycled through the red light came on but this time it had both the red and the yellow illuminated instead of just the red...so i gues my question is how do i stop this from happening and make it operate like it first was?..and..once that problem is figured...how do i speed up the yellow to red light change?...i included the diagram i used...everything is layed out to what it shows for the exception of the 1MΩ variable resistor...i used a fixed 1MΩ..and i also didnt use the .1 μf capacitor...thanks for reading...and as always thanks for your time...
     
  2. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    I've never liked schematics where they rearrange the natural order of the outputs to make drawing easier. It's not worth the trouble it causes in understanding and wiring. Do you have a diode backwards somewhere?
     
  3. the kidson

    Thread Starter Member

    May 15, 2011
    32
    0
    thanks for your reply....i checked and checked..all diodes were in right...i solved the problem for the red and yellow led being on at the same time..i just disconnected pin 10...but i still havent solved the prolonged yellow light problem..i removed the diode and just used pin 11 for the yellow light..but it is still the same..when the light goes from yellow to red...the yellow light will remain on for apprx. 15 seconds before changing to red...ideally i want a 3 second delay..not a 15 second delay...any ideas??..again thanks for your help
     
  4. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Hi the kidson,

    First, add the 0.1uF capacitor. This helps eliminate noise and gremlins.

    Second, doing a quick search for 555 astable timing calculators, it appears with fixed 1MΩ and 100kΩ resistors and a 10uF capacitor, your high clock pulse is almost 8 seconds and your low clock pulse is almost 7 seconds. Since the 4017 doesn't change state until the next high clock pulse, each output should be on for almost 15 seconds.

    If you want it less, use a variable 1MΩ resistor in place of the fixed one and dial it down or simply experiment with a lower resistor value.

    If you want it on for 3 seconds, then try using something between 150kΩ-180kΩ in place of the 1MΩ resistor and keep everything else the same. This should drop it down to about 3 seconds. Note this will affect all of your outputs, so the green and red LEDs will be on less also.
     
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  5. the kidson

    Thread Starter Member

    May 15, 2011
    32
    0
    thanks much for your reply Elec Mech..i figured this out last night when i was putzing with it...i just kept lowering the resistor value until it became more so what i was looking for...i ended up putting a 220k resistor in...but will try the values you recommended since the220k is still a bit too long...and yea..i noticed that the red and greens were shorter as well....thats fine...the circuit is being used for a traffic pole in a 1:18 scale diorama...again...thanks for the explanation and your time...
     
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