1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Relays and Mains Power

Discussion in 'High Voltage' started by jst3712, Jul 23, 2011.

  1. jst3712

    jst3712 New Member

    Joined:
    Sep 28, 2008
    Messages:
    60
    Likes:
    0
    Location:
    Melbourne, Australia
    If I use a DPDT relay (one suitable for switching mains), is it safe to have the relay switch 240V mains power via one contact ('Active' line), and 12V via the second contact? I am trying to avoid using 2 separate relays.
    If you think it's quite safe, is it possible that the 240V could arc over to the other contact inside the relay? If so, is there something I can do to avoid this? For example, a capacitor in parallel perhaps?

    Note: The relay is simply switching on/off a low-power battery charger (specs say 'Input=230-240V ~ 0.1A'), so we're not talking very high currents here.
    I won't go into great detail here as to why I am switching 240V and 12V.

    Thanks.
     
    Last edited: Jul 23, 2011
  2. Pommie

    Pommie Well-Known Member Most Helpful Member

    Joined:
    Mar 18, 2005
    Messages:
    10,019
    Likes:
    317
    Location:
    Brisbane Australia
    On the basis that it is "normal" to switch live and neutral with that relay then the isolation between the poles is good enough for 240V.

    Mike.
     
  3. jst3712

    jst3712 New Member

    Joined:
    Sep 28, 2008
    Messages:
    60
    Likes:
    0
    Location:
    Melbourne, Australia
    Thanks Mike. I agree, but I just wanted to be sure :)
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. squishy36

    squishy36 New Member

    Joined:
    Jul 22, 2011
    Messages:
    164
    Likes:
    9

    As a point of interest, realize that a relay rated for switching, say, a 10 A load at 120/240 VAC may not work well/reliably with lower voltage/lower current loads. My judgment says your 12 V 0.1 A load will probably work OK, but it's good to be aware of the different operating regimes of relay contacts from dry circuit applications up to heavy current switching. Some web searching will uncover more details if you're interested.
     
  6. jst3712

    jst3712 New Member

    Joined:
    Sep 28, 2008
    Messages:
    60
    Likes:
    0
    Location:
    Melbourne, Australia
    Hi "Squishy36". Thanks for your input - noted.
    The 240V load will be around 0.1A and the 12V load will probably be no higher than 0.6A. I'll see how I go with it, but I doubt my circuit will be sensitive to this particular switching method. But if fails, I will definitely have a look on Google :) Cheers.
     

Share This Page