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Latching relay

  1. Mar 12, 2010 #1
    Hey guys. I bought this relay


    It is supposed to operate at 11 mA. My question is, this thing has 8 pins, and I cannot find a diagram with what pin is what. Does anyone know what sort of configuration I would need just to simply turn on/off a load through the coils?


  2. jcsd
  3. Mar 12, 2010 #2


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    The two pins off by themselves are the input coil. Since the switch is DPDT, each switch has 3 pins. So I'm guessing that each of the two sets of three pins forms the switch, with the middle pin the common. A little time with a DVM and your power source switching the relay back and forth will let you beep out the pinout of the switches.
  4. Mar 12, 2010 #3
    Thanks. I am trying to use this relay to switch something on or off. I can get the coil to switch back and forth, but applying positive voltage pulses will switch it on once (any subsequent positive pulses have no effect), then require a NEGATIVE pulse to switch it off. Do you know if there is any way to cause a single positive pulse to either switch on/off the relay?

    Thanks again
  5. Mar 12, 2010 #4


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    As a latching relay, you might have to reverse the polarity of the voltage on the coil to make it switch.

    I have a number of these and the difficulty of reversing polarity outweighs the fact that it needs no current to hold the contacts in either position once it has switched.

    EDIT: sorry, I didn't see your comment Jbord. You could use the contacts of the relay to reverse the polarity, but it would need both sets of contacts and this would not leave you with any useful contacts for your project. This would probably produce a buzzer effect as the relay would switch rapidly to each mode.
    Last edited: Mar 12, 2010
  6. Mar 12, 2010 #5
    Dang. What sort of setup would I need to use singular pulses to turn on or off something? I have a reed relay, a regular relay, and two latching relays (if any of these can be utilized).

    The problem with the regular relays is that I am using a 38kHz IR receiver to switch the relay on/off, and the receiver innately will "turn-on" only for the first 14 pulses of the IR light (which is continuous).

    I thought this would be an advantage for switching on/off a latching relay, but I did not realize that the latching relay required a negative voltage to switch.
  7. Mar 12, 2010 #6
    Do you think this circuit could be adapted for my use?

    A reed relay which is activated for about (14 pulses)*(1/38000) = 368 uS.

    This relay (which is switching on and off as expected) could be used to power another circuit such as:


    My question is, do you think that substituting a 368uS "push" would even give adequate time for the capacitors to charge, and therefore switch correctly? Obviously the circuit was designed for humans pushing the button, and I expect most people push down on a button for more than 368uS.

    Thanks again everyone; you are awesome.
  8. Mar 12, 2010 #7


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    If you have two latching relays, it seems you could use one for the direction control (for both relays), and one for your functionality. I haven't thought it all the way through, though, so I could be wrong.

    You could use a flip-flop (FF) as long as it always stayed powered, and an H-bridge IC to drive the coil of a single latching relay...
  9. Mar 12, 2010 #8
  10. Mar 12, 2010 #9
    Thanks guys. Any idea if that circuit could work (before I buy the components)?

    Thanks again,

  11. Mar 12, 2010 #10


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    This circuit uses a monostable 555 to produce a 1/2 second pulse from a brief burst of 38 KHz infra red input.
    Although it was intended to drive a camera shutter, it may suit your purposes, depending on what they are.

    http://dl.dropbox.com/u/4222062/IR%20rec%20and%20monostable.JPG [Broken]

    A caution, though. I would expect that the output of the IR receiver would need a pullup resistor of about 4.7 K to the 5 volt supply. Your IR receiver may or may not work like that.
    The 7555 certainly expects a falling pulse to trigger as a monostable.

    This picture is from the Australian "Silicon Chip" magazine.

    To change the delay you could change the components that go to pins 6 and 7 of the 7555. Making them bigger increases the delay.
    Pin 3 of the 7555 goes high for some period determined by these components and then drops to a low value again.

    When your receive chip goes low and then high, how long is it before it can go low again?
    Last edited by a moderator: May 4, 2017
  12. Mar 13, 2010 #11
    The IR receiver can go back to 0V as soon as the signal is stopped. Example: moving my hand with fingers open triggers it each time a finger breaks the signal.

    Rather than worry about using the IR receiver, I think it would really simplify the circuit to use a circuit I already have using a reed relay to switch something else on or off.

    How could I modify the above circuit to just use a single toggle from the reed relay instead of the IR receiver?

    Thanks so much again.
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