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CD4017 Driving a Relay

Discussion in 'General Electronics' started by prizark, Mar 6, 2004.

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  1. prizark

    prizark Guest

    Hi guys,

    I am using the CD4017 Johnson decade counter in on of my
    experiments.I want to turn the relay on during the 4th to 6th clock
    pulses of the counting.So I used an OR gate to input the "output 4",
    "output 5" and "output 6" of the 4017 to drive the realy from there.
    The OR gate is made by using DL(Diode Logic) just a couple of zener
    diodes and a pulldown resistor. I know that the output driving current
    of the CD4017 is not more than 9mA but it is sufficient to drive and
    transistor into saturation and switch on the relay. But for some
    reason that is not happening. The circuit is able to drive LED's with
    and without transistor at the output but not the relay.The relay is a
    6V/100 Ohms type.I even tried using a Darlington pair and also the
    intergrated version of the Darlington pair(ULN2803) but couldn't make
    things any better. What could be the problem.

  2. Kevin Weddle

    Kevin Weddle Guest

    A zener diode doesn't guarantee 5 volts. It will produce 5 volts when
    the voltage exceeds 5 volts.
  3. Kevin Weddle

    Kevin Weddle Guest

    Also, if the logic is alright, the diodes still require a minimum current.
  4. Try replacing the zener diodes with a couple of small signal diodes such
    as 1N4148 or 1N914. If I understand what you are saying I fail to see
    why you are using zeners.
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