control a latching relay with one switch?

Discussion in 'General Electronics Chat' started by anne, May 27, 2008.

  1. anne

    Thread Starter Active Member

    Apr 20, 2008
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    asdasdadassdas
     
    Last edited: Jun 1, 2008
  2. Caveman

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    Apr 15, 2008
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    There is a way, but I've got to try to remember, it basically involves passing the current back and forth through a capacitor. I'll try to get back to you within the day to let you know if I remember.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    Single coil is the only one that will work with one switch. How much of a load are you switching? I've been using a P & B 12 volt latching relay to run a set of lights in my basement for 8 years. From 5 locations, at that (all the pushbutton switches are in parallel).
     
  4. Pich

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    Mar 11, 2008
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  5. anne

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    Apr 20, 2008
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    asadasadssadsadsa
     
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  6. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Here's a push-on/push-off circuit with a standard-relay that I always considered slick. :)

    http://radiomagonline.com/notebook/radio_pushonpushoff_switch_2/

    The main criteria is that the DC supply voltage is twice the coil voltage (24v for a 12v relay...12v for a 6v relay...~9v for a 5v relay), and R1 = R2 = Rcoil. You can play with the capacitor for physical size vs. reliable operation.

    Ken
     
  7. anne

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    Apr 20, 2008
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  8. beenthere

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    Check the Potter & Brumfield S89R11DAC1-12 impulse latching relay. It changes state with each application of voltage - no polarity reversal needed. It's goo for 15 maps @ 120 VAC. A momentary pushbutton switch is all it needs, along with the coil voltage.

    I see your problem now. These are way too big for your application. You may need to use KMoffett's trick.

    Another thought - if this is a weenie DIP relay, you might think about using a flip-flop that is toggled by the switch. Each debounced press of the switch toggles the flip-flop to the next state, supplying of cutting off current to the relay coil.
     
    Last edited: May 28, 2008
  9. anne

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    Apr 20, 2008
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    qweqweqweqwqqeeqewqe
     
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  10. SgtWookie

    Expert

    Jul 17, 2007
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    Hello Anne,
    Have you considered push-on, push-off switches to control the relay's coil?
    [​IMG]

    Since the length of the button's exposed shaft changes, you really wouldn't need a lit indicator - unless you wanted to be able to observe it while wearing a welder's mask. A small LED with a suitable current limiting resistor would serve in that regard.
    Ebay auction:
    http://cgi.ebay.com/10-Miniature-DP...oryZ4660QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

    You could use this switch to control the coil of a low-voltage relay. This one is DPDT; each contact rated 100mA @ 30v
     
    Last edited: May 28, 2008
  11. gerty

    AAC Fanatic!

    Aug 30, 2007
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    I wouldn't give them a second thought, if people don't like my question, it's their problem not mine. Sarge's fix seems to be the easiest..
     
  12. SgtWookie

    Expert

    Jul 17, 2007
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    Quite a bargain!

    The problem with using flip-flops is that they would "forget" their logic state when the power was turned off.
    An example of a Dual-D Flip Flop would be a CMOS 4000-series 4013, or CD4013B (many different manufacturer part numbers), a J-K Flip Flop would be a 4027 (CD4027B) etc. But, unless you kept them supplied with voltage, they'd "forget".

    Everyone's been there at least several times. If they deny, they lie. ;)
     
  13. anne

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    Apr 20, 2008
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    wqerwerwqewewerwe
     
    Last edited: Jun 1, 2008
  14. beenthere

    Retired Moderator

    Apr 20, 2004
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    The short answer is no. The contacts will burn with too much current, and they may not separate enough to stop arcing with 120 VAC applied. You may have to consider a solid state relay to keep package size down. You could use a pushbutton switch, but it would have to be alternate action (maintained contact).
     
  15. SgtWookie

    Expert

    Jul 17, 2007
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    The type of switch I posted is in common use on items like test equipment (oscilloscopes, frequency counters, etc.) No, it would not be suitable for 120v switching, but would be for 24v, 12v, 6v, 5v, etc. I do know that Skycraft Surplus has (or had) in stock some VERY small 120v to 6.3v or 7.5v transformers, which might be used to supply current to this switch, to power a relay's coil. I do not recommend running a component at it's maximum ratings, as it's lifespan will be considerably diminished.

    You seem to have your mind set on a switch-controlled relay. Would it be possible for you to consider something like a micro SPST, DPST, or DPDT toggle switch? Sometimes the simplest route is the best.

    I don't know if this is the same project you were working on before, but I suspect that your space constraints are rather tight. Cost is always a factor.

    Those tiny latching relays you found seem rather promising. Price is right, too.
     
  16. Wendy

    Moderator

    Mar 24, 2008
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    That same low power switch could handle a Solid State Relay also, which are pretty easy to use.
     
  17. anne

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    Apr 20, 2008
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    qwreqweqweqweqe
     
    Last edited: Jun 1, 2008
  18. anne

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    Apr 20, 2008
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    XXXXXxXXXXXx
     
    Last edited: May 31, 2008
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