This relay shouldn't chatter but does!

Discussion in 'General Electronics Chat' started by Meat, Dec 13, 2014.

  1. Meat

    Thread Starter New Member

    Dec 13, 2014
    9
    1
    Hi,
    I've designed a basic circuit to allow the automatic switching of input when connecting to an external source. Let me explain a bit better; I have a van that I am converting to a camper. It has a consumer unit that I want to be able to supply from either the inverter or an external source (hook up). So instead of having switches that need to be manually operated, I have designed a circuit that takes the input AC voltage as the latching power to a 3PDT ac relay. The relay I'm using is JQX-38F series -40A-AC1.Here is the link to the relay I bought.

    http://www.amazon.co.uk/gp/product/B009N7WVM6?psc=1&redirect=true&ref_=oh_aui_detailpage_o05_s00

    The relaxed position connects the inverter to the consumer unit. There are no other components in the circuit. When I connected the external source, the relay 'chattered' so loudly it sounded more like a dentists drill! Its as if the relay is a DC coil relay, but it has actually got AC220V written on the coil. The supply is 240Vac; could this be the problem?
    I thought that maybe I could put a diode between the coil inputs.

    Has anyone got any ideas or have i missed something obvious?
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Show us how you connected the relay.
    Seems to me your connection is somewhat wrong for your app.
     
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    One problem that can exist is that once the 12v coil of the relay is energized and the relay contact is made, the load on the 12v power source is so high that the supply sags below 12 volts. At that point, the coil magnet cannot maintain the contact and it switches off. As soon as it switches off, there is enough voltage to re-establish contact... and repeat... and vibration!

    If this is the case, your load is too high
    ...or your 12v power supply is not string enough (sags too easily)
    ...or your relay coil is questionable.
     
  4. Meat

    Thread Starter New Member

    Dec 13, 2014
    9
    1
    R!F@@
    Here is a basic drawing of how Ive connected it up.
    Lets hope this works
    Relay Connection.pdf
     
  5. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,999
    745
    So your trying to run your camper from a 12v inverter, then when hooked up to camp site mains, the relay connects the camper sockets to the hook up,and disconnects the inverter.
     
  6. Meat

    Thread Starter New Member

    Dec 13, 2014
    9
    1
    GopherT,
    This is an AC Relay though, rated to 220VAC. It is acting like a DC coil with the chattering, but, unless I've been duped, I bought it as an AC coil relay.
     
  7. Meat

    Thread Starter New Member

    Dec 13, 2014
    9
    1
    Dodgydave,
    Exactly. When the relay is relaxed, it reconnects the inverter to the consumer unit, providing AC to the van. I've got a low power AC fridge so would like this to run when 'wild' camping.
     
  8. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    @Meat Is it clicking for both mains power AND battery power?

    Which is the default (when coil is NOT energized). Mains or battery?

    A low fraction of all relays can operate with AC power to the coil. Most need a DC source to the coil.

    Please advise...
     
  9. Meat

    Thread Starter New Member

    Dec 13, 2014
    9
    1
    @GopherT
    There is no DC applied to the relay. Have a look at the crude drawing I did in post #4. The NC Contacts are connected to the AC output from the inverter. The energised contacts are connected to the AC input from the external source; this source is tapped off Live and Neutral to supply coil power to the relay. the common contacts feed the consumer unit and breaker board.
     
  10. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Relay connection seems good.
    If it is rated properly and if it is indeed an ACV Relay, then it should not chatter.

    Try just connecting the Relay coil to mains 220VAC and see if it chatters
     
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The relay from the amazon post is AC coil.
    I don't know what is going on unless you have a bad connection somewhere and you have a thermally induced open/short when the coil is activated.
     
  12. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    i think your problem is the relay is picking up the ac from the inverter and trying to disconnect it at the same time, you need to post your wiring diagram.
     
  13. ramancini8

    Member

    Jul 18, 2012
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    I suspect, from info in post 9, that you are only using 120V.
     
  14. Meat

    Thread Starter New Member

    Dec 13, 2014
    9
    1
    Thank you for all your help. So, I plugged the relay directly into the mains supply (tentatively) @ 240VAC (in the UK) and no surprise, the relay acted exactly as it had been, chattering away like a tattoo gun! I swapped polarities and of course this made no difference. With this particular relay, the cap is removable and you can get to the components inside. I had a thought that the contact springs may be too far set towards the opposite contact so when the relay makes, the contacts 'make' too soon and there is too much tension in the springs so when the magnetic field drops the contact arm is not held and drops off until the next the next cycle. Well I gave it a wiggle and a squeeze and a poke (unplugged of course!) and tried it again. SUCCESS!! It seems to work now as it should. Holds like a dream with no chattering or vibration of any sort. Now just got to try it in the van and make sure its still OK.
    I want to thank you all for your inputs, it gave me confidence and reassurance when mine was waning!

    As more projects develop, i am sure to tap all your brains again.
     
  15. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Nice Santa aviator, @ramancini8 !
     
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Maybe the shading ring is defective, open or missing?
    According to the specs, the hysteresis for that relay on 240vac is P.U. at 176vac, D.O. 72vac coil res 3380.
    Max.
     
  17. Meat

    Thread Starter New Member

    Dec 13, 2014
    9
    1
    See you've lost me now! I know what hysteresis is but the figures you're quoting mean nothing to mean. I have measured the coil resistance and it is a little over 3400.
    Is the shading ring the part that looks like a 'D' shaped washer? If so, it looks ok under inspection.
     
  18. Meat

    Thread Starter New Member

    Dec 13, 2014
    9
    1
    Ahh ok, Power Up 176Vac and Power Off 72Vac. I get it.

    I'm going to check it in the van and I'll let you know how it goes.
     
  19. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Yes I had posted without seeing you had cured the problem.
    The shading ring is a shorted copper single turn close to the coil, and produces a phase shift in that part of the coil in order to keep the armature attracted when the current transitions through zero.
    P.U. 176ac is the AC value point that the relay will pick up, conversely the D.O. 72 means it will drop out when the voltage drops to 72vac.
    Max.
     
  20. sdowney717

    Member

    Jul 18, 2012
    391
    13
    http://www.amazon.com/STRUTHERS-DUN...F8&qid=1418500907&sr=8-3&keywords=pm-17ay-240
    I have three of these with 120vac coil and so far they have worked ok. I boguth them off ebay for mid 20 - 30$ range. I did change out the too short screws for my copper lugs.

    The relay you bought, I dont like those push on terminals. Also your using for wires when it says PCB?
    Does that mean the intention is to be soldered onto a pcb board?

    I dont understand how that
    JQX-38F AC 220V Coil 11 Pin 3PDT PCB Type Power Relay 40A

    relay can have a 40 amp rating. To me the pm17ay type are heavier duty. I mean the lugs, they are thick, no way you can bend them.
     
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