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Relay Chatter

Discussion in 'General Electronics Discussion' started by dssteven, Aug 14, 2012.

  1. dssteven

    dssteven

    47
    0
    May 9, 2012
    Hey guys,

    I am running a very simple circuit with a Amperite HDFA Timer turning a relay on and off which in turn activates a vibrator motor. I'm using a 30A adjustable DC power supply. Anyways, when the timer turns the vibrator motor on the relay makes a buzzing sound (not just the click like normal). I'm wondering if anybody has any clue as to why I'm getting this chatter and what a possible cause/solution might be. The schematic is below.

    [​IMG]

    Timer: http://www.amperite.com/assets/Documents/hdfa.PDF
    Relay: Simple 12V SPDT Relay
    PS: http://www.bkprecision.com/products...high-current-dc-power-supply-0-32v-0-30a.html

    I can't find the specs on the vibrator motor but it is just a simple electric motor that rotates two counterbalanced disks to vibrate. It pulls 4-5A, more if you push down on the vibrator or put a load on it that makes it harder to vibrate.

    Let me know if there is anything else you guys need to know. I'm going to keep digging on this myself but google is providing me with a lot of AC relay chatter and not a whole lot on DC and then the people just say it's because voltage isn't high enough over the coil but I've got my PS set at 13.5V since that is what the vibrator motor runs on normally.

    EDIT: By the way, the only reason I'm running a relay with the timer is so I don't have to run the vibrator motor current directly through the timer. Those things aren't cheap and it is possible for the vibrator, under a very large load, to pull 9-10A so I'd just rather not risk it.

    Thanks!

    Dan
     

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    Last edited: Aug 14, 2012
  2. GreenGiant

    GreenGiant

    830
    5
    Feb 9, 2012
    for starters its good to get in the habit of putting motors and things on the NO connection of a relay, that way it doesnt automatically energize when power is applied.

    What are the exact specs of the timer that you have? the designator codes I mean
     
  3. dssteven

    dssteven

    47
    0
    May 9, 2012
    Whoops, it is on the NO connection, my mistake on the schematic. The timer has two pots, one for on and one for off, naturally. I have them turned to go 20s on, 10s off. It is the CHDFA version. "C: .6 to 60 seconds" Specifically, it is the 12V DC CHDFA
     
    Last edited: Aug 14, 2012
  4. dssteven

    dssteven

    47
    0
    May 9, 2012
    I updated the original post to reflect the correct connections. Thanks for pointing that out GreenGiant
     
  5. dssteven

    dssteven

    47
    0
    May 9, 2012
    It seems the motor is the issue, it clicks on and off fine when the motor isn't connected. Would this make sense? And why would the motor cause this chattering?
     
  6. GreenGiant

    GreenGiant

    830
    5
    Feb 9, 2012
    Have you measured the voltage across the motor when it is running?

    How is the motor positioned? horizontal or vertical?

    If you have it positioned horizontally then it will take more energy to move the weight up, then when it reached its peak it will draw virtually nothing on its downward travel, this could cause current/voltage fluctuations enough to affect the coil of the "Main" relay.

    Try putting a capacitor across the motor connections, something like... 100uF or so rated at 30V+ that might help clear up the issue
     
  7. dssteven

    dssteven

    47
    0
    May 9, 2012
    Voltage across the motor when it is running is 13.5V

    It's positioned vertically

    I'm sure a cap would work, I'll give it a shot. Thanks
     
  8. dssteven

    dssteven

    47
    0
    May 9, 2012
    Cap killed it! 100uF Cap per suggestion. Worked like a charm! Thanks Green Giant
     
  9. GreenGiant

    GreenGiant

    830
    5
    Feb 9, 2012
    Glad to hear that worked.

    You could also put the cap on the coil of the relay as well, that would have a similar effect, only that would cause a slight delay in the switching of the relay when you remove power
     
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