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Beginner Relay Question

Discussion in 'Electronic Basics' started by AB, Mar 9, 2007.

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  1. AB

    AB Guest

    Hi all,
    I'm playing around with some relays and need some guidance.

    I have this relay:

    It's not going on a circuit board. I'm planning to just solder some
    wires to the contacts with a 25 watt pencil iron.

    Do I need to use a heat sink to protect the relay coils and contacts
  2. Rich Grise

    Rich Grise Guest

    Not if you use small wire (maybe #22-24), wrap it around the end of the
    post, and don't linger too long (use a hot enough iron, and solder it
    quickly; if you get a cold joint, let it cool completely before you try

    Make sure everything's clean and shiny, and use a good flux-core solder,
    like Kester 63-37, which RS also has.

    Have Fun!
  3. jasen

    jasen Guest

    No heatsink is needed. If you can make the joins with less than
    about 5 seconds of direct heat on each pin (which shouldn't be
    difficult) the relay will survive.
  4. Ross Herbert

    Ross Herbert Guest

    Many of the cheaper relays have their pins in plastic which won't take
    direct soldering. Anything more than 2 seconds will see the pin being
    soldered wilt sideways. If this happens you have to let it cool and
    then judiciously apply more heat while straightening the pin and
    holding it with pliers for a few seconds until it is once again in its
    normal alignment. They are fine when mounted to a pcb and up to 4 or 5
    seconds can be tolerated because the copper traces act as a heatsink.
  5. Probably not. I think this unit is designed to be soldered
    onto a printed circuit board, so it is designed to have its
    pins soldered.
  6. Bruce

    Bruce Guest

    Hi Bob,

    I've use this same relay for several projects, and never had a problem with
    soldering wires to leads or mounting them on boards.


  7. Rich Grise

    Rich Grise Guest

    I'm sorry to bust your bubble, but this is really more a matter of
    technique, albeit 2 seconds should be enough time for any small solder
    joint like these.

    The secret, of course, is the same as the route to Carnegie Hall:
    Practice, practice, practice. :)

  8. Ross Herbert

    Ross Herbert Guest

    Rich, I totally agree with your conclusions re practice...... However,
    the OP said he was a "beginner' and thus is not likely to have yet
    learned the hard way how to achieve perfectly soldered joints in under
    2 seconds. Even then, the wattage and/or the type of soldering iron he
    has will be relevant and we don't know what he has available. For
    example, if he uses a 60W non temp controlled iron the plastic will
    allow even less than 2 seconds of heating before the pin sags.

    During my professional tech days we always used high quality switches
    by C&K (circa 1970 - 80's) and the contacts on these would allow quite
    long periods of heating without any damage or plastic melting. They
    could be soldered and unsoldered many times by a technician properly
    trained in soldering techniques. When I had to buy some small switches
    a few years back - they looked to be good quality, and appeared
    identical in style to the old C&K's, I discovered very quickly that
    even with my experience it was easy to get the pins to sag with only
    quite short periods of heat application. They were certainly designed
    for one attempt only and it would be impossible to unsolder and re-use
    these switches.

    That is what I was referring to with the RS relay and what the OP had
    to be aware of.
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