2 position relay

Discussion in 'General Electronics Chat' started by #12, Dec 26, 2012.

  1. #12

    Thread Starter Expert

    Nov 30, 2010
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    I need a relay that alternates betwen 2 positions and don't know what to call it in my searching. 120VAC coil, SPST. Power the coil for about 1/2 second and the contacts land on "open". Pulse the coil again and it lands on "closed". 15 amp minimum load at 120 VAC where 120 VAC means American power line voltage from 110 to 125 VAC, 60 Hz.

    What do you call this? PS, actually naming who sells them would be nice.

    Thank you...
     
  2. tracecom

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    Apr 16, 2010
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    I think you may be looking for a latching relay.
     
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  3. crutschow

    Expert

    Mar 14, 2008
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    If the pulse is to the same coil with the same polarity, then that would be a ratchet relay.
     
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  4. #12

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    I have also found, "bistable" and "impulse" associated with these relays.
    I have also found $46 associated with these relays! Obviously, I have more searching to do.
    I would consider making one from the buckets full of "normal" relays that I have laying around.
    Probably just requires a bit of thinking.
     
  5. kubeek

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    If you don´t require the zero power consumption of latching relays, then it should be quite doable.
     
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  6. tracecom

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    You can make a relay latch through its own contacts as shown in the attachment.
     
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  7. strantor

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    What you describe, I have found to be called an Impulse Relay, and for $46 I think you've discovered the lower end of the price range.
     
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  8. #12

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    $46? Ouch! Makes me think about using a D flip-flop.

    Making a latching relay is easy enough: on, stay on, wait until power is not available, unlatch. What I'm doing is, on, stay on, wait until power is off, stay on, wait until power comes on again, then turn off, then stay off after power is gone, then see power again, then turn back on. It's the flippen-floppen that requires cunning. The only must-have is that it responds to the 120 VAC input, twice. I can supply a DC voltage, run the 120 through a step-down transformer, rectify, filter, add transistors, or whatever I have in my junque box. There are obviously a dozen ways to skin this cat, and half a dozen watts means nothing compared to the 2 killowatts it will control.

    So...thanks for the input. I'm on the right track now.

    PS, I got detoured by a virus. Considering the clunking noises the hard drive has been making for a few months, and 6 partitions wiped by the virus, I decided to Frisbee the HDD. Now I'm using a backup HDD that hasn't seen an update for over a year. It just found the DL DVD read/write and the 24 inch LCD flat screen. A few more shut-down/restarts and it should be up to speed.
     
  9. strantor

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    The need for this type of relay actually comes up a lot on the forum. I can't count how many times I've told people "what you're looking for is an 'Impulse Relay" and then they come back saying "well that's too much to spend on my DIY _______ (irrigation system, chicken coop, etc.) do you have any other ideas?"

    If you figure out how to do this with a couple ICs and relay, please, post a blog about it so we can reference people back to it every time it comes up in the future.

    I would start with a dual coil latching relay and a 555 one-shot and go from there, but I'm not sure where I would go from there.
     
  10. kubeek

    AAC Fanatic!

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    For a latching relay, I would simply go with what tracecom posted, and use two other relays for the NO and NC switches.
    Or do you need the thing that on one pulse latches on, and on other pulse on the same wire latches off?
     
  11. strantor

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    This:
    ...................................
     
  12. Jeauxm

    Member

    May 8, 2013
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    Try looking for 2 Coil Latching Relay. I bought some from Digikey Part# 225-2854-ND.

    There are 2 coils - one on each end - there are two separate coil connections. These have a "memory" as in they stay where you set them even when the power is removed. Kinda like a one shot. Hope this helps.
     
  13. rsfoto

    Member

    May 14, 2013
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    Hi,

    I am using similar relays were I apply a one second pulse and it closes and then again for opening another one second pulse. This are the one I am using

    The pulse length of 1 escond is not a must, half a second as you write will do it too.

    http://gfinder.findernet.com//assets/Series/384/S19EN.pdf

    Hope it helps.

    regards Rainer
     
  14. JayArr

    New Member

    Mar 11, 2013
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    Google is your friend:

    I got this from another site:

    Relay Flip-Flop
    There comes a time when on/off control of power to a load needs to be accomplished with one pushbutton switch. Drag out the junque box! All you'll need are two DPDT relays, two resistors, and an N.O. pushbutton switch
    [​IMG]
    Parts
    K1, K2 DPDT coil voltage = Vsource/2
    R see text
    S1 SPDT N.O.
    When S1 is closed, K1 is connected directly across the voltage source and pulls in. Because its coil is rated at half the source, the switch closure must be momentary. K1A closes and pulls in K2, and the coils are now in series. Contacts K1B are connected to the load circuit, which can be an entirely different circuit from the relay source. When S1 is pressed again, it shunts the coil of K2, which drops out and the load is disconnected.
    Most reasonable-quality relays can withstand twice their coil voltage for short times. However, if you want high-reliability operation, insert a resistor in each coil circuit as shown. The resistor value should be chosen on the basis of relay pull-in voltage and coil current. One desirable feature of a relay is that it will remain pulled in at considerably less than rated coil voltage.
    This has worked for me:
    1. With a variable voltage source, determine the lowest pull-in voltage V1.
    2. Add about 20% of V1 and call it "on".
    3. With the relay pulled in, slowly lower the voltage to determine drop-out voltage V2.
    4. Add about 20% of V2 and call it "off".
    5. The idle, or holding, voltage would be halfway between V1 and V2.
    6. Calculate value and power rating based on holding voltage and current.
    73 de WB4FXD




    http://www.taars.us/TechNotes/relayf-f/Relay%20Flip-Flop.htm

    Addendum: If you need to activate it with a voltage pulse instead of a switch just add another relay and use it's contacts for the pushbutton.
     
    Last edited: May 17, 2013
  15. #12

    Thread Starter Expert

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    Please do not answer threads that are several months old.
     
  16. JayArr

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    Mar 11, 2013
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    Sorry, it was at the top of the stack so I thought it was current.
     
  17. #12

    Thread Starter Expert

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    We all make that mistake. Whomever notices the thread is out of date posts a "stop notice". No big deal.
     
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