how do you keep the switch on ?

Discussion in 'General Electronics Chat' started by Jaycarnewbie, Apr 17, 2007.

  1. Jaycarnewbie

    Thread Starter New Member

    Apr 15, 2007
    7
    0
    If you want a circuit to close using a remote ,and stay that way using a relay how do you go about it. the signal from say a UHF transmision, or even the current generated from rining a mobile phone is used to do what ? Activate a transistors base ?
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,140
    1,789
    In relay ladder logic it's called a sealing contact. Put a NO relay contact in parallel with the switch. When the switch is closed energising the coil the NO contact associated with that coil provides a parallel path. To de energise the coil an NC switch/contact is placed in series with the parallel combination of the switch and the sealing contact. See the following link for a drawing.
    http://www.seattlerobotics.org/encoder/may97/ladder1.htm
     
  3. John Luciani

    Active Member

    Apr 3, 2007
    477
    0
    You could use a latching relay. Check out Digikey for specs.

    (* jcl *)

    ---
    www.luciani.org
     
  4. Tube Tech

    Active Member

    Jan 11, 2007
    46
    0
    Use a DPST or DPDT relay. Use one set of contacts to switch the load. Supply the common side of the other contact with the voltage used by the relay coil, and feed the NO side to the relay coil. When the relay energizes, the second set of contacts latches the relay. Stays that way until power or ground is interrupted.
     
  5. Jaycarnewbie

    Thread Starter New Member

    Apr 15, 2007
    7
    0
    thanks for those responses.
     
  6. Jaycarnewbie

    Thread Starter New Member

    Apr 15, 2007
    7
    0
    I used two single pole relays, a 12 volt bulb and battery.(and a 9v to jump start) The way its wired up I dint think it was going to matter which relay I 'jump started". But it does. Only one particular relay can be started which will keep the circuit closed. It is the one which has zero voltage drop on its switch circuit.where as the other has 5 or 6v.
    Im still figuring out how its working but way ahead of yesterday.
    Now I think a third relay which is normally closed and would have a separate signal to open. Sounds messy ?
     
  7. Tube Tech

    Active Member

    Jan 11, 2007
    46
    0
    2 attached images of latching relays.

    to unlatch one, interrupt power to the latching contact.

    to unlatch a whole group, tie all the return sides of the coils to a common ground, run that through a switch or relay. open that common path to clear all.
     
Loading...