interference and ne555 and relays

Discussion in 'Digital Circuit Design' started by bend94, Jul 5, 2016.

  1. bend94

    Thread Starter New Member

    Feb 15, 2016
    13
    0
    Hi everyone,

    i did a first circuit with Timer NE555 managing a relay1.
    i did another circuit with another relay2.

    all is working well except in this case :

    when relay1 is on (Timer555 is running) and relay2 is on. If i put relay2 off , the NE555 seems to reset the timer as a result the relay1 become off.

    Someone can help ?
    Regards
     
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,931
    382
    Do you have a catch diode across the relay coils?
    Do you have a decoupling capacitor across the NE555 supply terminals very close to the IC?
    Do you have a decoupling capacitor on the NE555 control voltage, pin 5?
     
  3. DickCappels

    Moderator

    Aug 21, 2008
    2,651
    632
    What is the relationship between the two relays? Please post a schematic diagram or at least a wiring diagram.
     
  4. bend94

    Thread Starter New Member

    Feb 15, 2016
    13
    0
    Well on the relay board there is a diode.
    what is a decoupling capacitor .? have you got an scheme example ?
     
  5. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,931
    382
    You should have a capacitor, say 100nF, from pin 5 to ground, and also between pins 8 and 1 (the chip supply voltage)
    Also, the reset pin, 4, should not be left floating. If unused it should be connected to supply.
     
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