switching 18Vdc

Discussion in 'The Projects Forum' started by stirling, Sep 7, 2010.

  1. stirling

    Thread Starter Member

    Mar 11, 2010
    To remotely fire a plasma torch the manual suggests I need to switch 18Vdc with either a relay or a SSR. It states the relay or SSR should be rated for 10mA. Is a relay or a SSR not a bit overkill for this? Your suggestions/advice very welcome.

    Sorry should have said: Control is from a PC parallel port

    Last edited: Sep 7, 2010
  2. Dyslexicbloke

    Well-Known Member

    Sep 4, 2010
    You will probably find that the suggestion is just to ensure complete isolation from the computer, or whatever.
    Although it is unlikly the 18V may not be relative to ground.
    More likly is that the ground may be noisy, due to the plasma current supply, so its control circuitry is decoupled and floating.

    Anyway driving a relay from a PC isnt hard ... In the unlikly event that there arnt loads already on this site I would be happy to sketch you one.

  3. stirling

    Thread Starter Member

    Mar 11, 2010
    Thanks - I'm ok with doing it with a relay just wondered if there was a "better" way.

    Re: SSRs - am I right in thinking they're not well suited to switching low currents like this - or have I made that up?