need help please with traffic light circuit..

Discussion in 'The Projects Forum' started by wayne pienaar, Jan 11, 2015.

  1. wayne pienaar

    Thread Starter New Member

    Jan 11, 2015
    hi guys.

    I'm very new to this electronic thing.

    i bought a life size traffic light the other day, that runs off 220v.

    i decided i wanted to automate it..

    so I've just finished building a traffic light with 2x 555 timers.
    connected to 3 led's and 3 relays to switch on the big lights.

    when i switch it on. all the led's come on, and stay on..
    i have not connected the big lights to the relays yet.

    so the LED's should change, and i should hear 'clicks' coming from the relays when the lights change color

    i used a diagram i got off the internet, and some help from a local electronics shop.

    i have used a 220v to 12v transformer, and a ad-dc converter and a L7809CV voltage regulator.

    so the 2 problems im having: all led's stay on all the time
    the voltage regulator gets quite hot..

    thanx in advance for getting it all working... (hopefully)

    20150111_183525.jpg 20150111_183534.jpg 20150111_183542.jpg 20150111_183754.jpg 20150111_184156.jpg .
  2. crutschow


    Mar 14, 2008
    Your schematic doesn't show the relays.

    Using two 555's the Red led will light in a random sequence from the orange and green. Is that what you want?
  3. wayneh


    Sep 9, 2010
    The schematic doesn't show how you have connected the relays, or how the regulator is hooked up. Are you getting a 9V supply to the first 555?

    I'd disconnect the relays altogether until you get things working with just the LEDs. And, disconnect the 2nd timer until you get the first one toggling. Divide and conquer.
    ebeowulf17 likes this.
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
    The basic timer circuit shown in the schematic seems okay. On power-up, it takes a bit to stabilize, but then settles into a pattern of:

    R on for about 8 seconds
    R off and G on for about 8 seconds
    G off and Y on for about 4 seconds
    Y off and R on for about 8 seconds

    I can't tell doodly about the rest of the connections, except the cap on the 2nd 555 looks like it's in backwards. And the relays have 12V coils and may not work on 9V.

    Post a schematic of how you have the power supply wired.
    Last edited: Jan 11, 2015
  5. wayne pienaar

    Thread Starter New Member

    Jan 11, 2015
    ok so for now ive disconnected the power supply, and used a plug in ac dc transformer, set to 9v.

    and ive cut off the wires going to the relays, untill i can get it working properly.

    i still have the same problem, as soon as i put it on, all the LED's light up, and stay on permanently..

    i also noticed that the second 555 thingy was warmer than the first one, after it had been on for a few seconds.

    i have re-checked all the connections and all seems to be fine...

    could it be 1 of the capacitors that is connected the wrong way? (polarity) or 1 of the resistors??

    i uploaded a pic of how it looks at the moment..

  6. tracecom

    AAC Fanatic!

    Apr 16, 2010
    100uF cap on right is in backwards. Resistors don't have polarity.
  7. wayne pienaar

    Thread Starter New Member

    Jan 11, 2015
    thank you..

    i changed it around..

    still not working.. still all leds on at the same time..

    if i take both 555 timers out, and connect the power. the green led comes on, and stays on... is that normal?
  8. absf

    Senior Member

    Dec 29, 2010
    Are you using stripboard? If so, did you cut the trace on the bottom side of the 100K and 47K resistors?

  9. wayne pienaar

    Thread Starter New Member

    Jan 11, 2015
    hi Allen.

    yes i used stripboard..

    yes i did cut the trace at the resistors..

  10. ebeowulf17

    Well-Known Member

    Aug 12, 2014

    I'm having a hard time tracing all the wires in the pics, but according to the schematic, with the 555 chips removed, the green LED should definitely not have any voltage source. It only connects to ground and to various 555 pins (and a cap which just goes back to ground.) Trace out all the connections on the positive side of the green LED and I bet you'll find your problem.
  11. wayne pienaar

    Thread Starter New Member

    Jan 11, 2015
    hi guys.. thanx so much for all the help.. i got the basic thing working, 3 leds flashing green, yellow, red..

    i used stripboard.. and the 100k and 47k resistor were on the same strip, i cut the trace where the resistors are, but not between the 2 resistors.. so they were making contact..

    now to get the relays workimg.. when i connect them, the cycle skips the yellow led, so only the red and green ones come on.

    i need to see if i can get relays with 9v coils...
  12. tracecom

    AAC Fanatic!

    Apr 16, 2010
    Your 555 circuit will work just fine on 12V.

    And the yellow LED is running off the reset -correction, discharge- pin, which is being called upon to sink current, and that current may exceed its capability. You may need a transistor driver in between the 555 and the relay. In fact, the other relay coils may be stressing the 555; I haven't done the calculations. And one more thing; you should consider EMF suppression diodes across all the relay coils.

    All my comments are speculation, since you haven't posted a schematic. Please be careful; 220v is dangerous.
    Last edited: Jan 12, 2015