help with 555 timer

Discussion in 'The Projects Forum' started by starrz, Jan 6, 2013.

  1. starrz

    Thread Starter New Member

    Jan 6, 2013
    hey everything is up and running, connected the relay and transistor but am not getting the latching effect when output two is high, the leds and well as of now relay, sticks when output two is connected to clock disable without even going high at all, as long as i connect any output whatsoever to clock disable it just sticks on, you said yours latched properly?
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
    I have the entire circuit built, including the relay. It works just like I described in post 30. When I disconnect the power and reconnect it, output 0 goes high for 2 seconds and the relay operates, then output 1 (which is connected to nothing) goes high for 2 seconds and the relay releases, then output 2 goes high, the relay operates and stays operated until I disconnect the power and reconnect it.

    Did you put the 1N400x diode across the relay coil?
  3. ScottWang


    Aug 23, 2012
    You can't connect LED to the output of CD4017, because it may make BJT not enough current to drive the relay.

    R5 can be reduce some more to 8.2K or 6.8K, some relay maybe draw too much current, so you should measure the resistor of Relay coil, and use I_relay = 12V/resistor_relay to calculate that how much current the relay would need.
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
    Here's a crappy video of the circuit working.

    In the video, the green PCB standing up is the 555 clock; the green LED on it indicates a high output from pin 3. It's running faster than you want, but I already had the circuit built.

    The three LEDs on the front of the breadboard indicate three outputs from the 4017: green = 0, yellow = 1, red = 2.

    The blue LED on the rear of the breadboard indicates an ON signal being sent to the relay.

    The relay is shown in front of the breadboard. If you listen closely, you can hear the relay operate: soft click = operate, louder click = release.
    Last edited: Jan 9, 2013