How to Reset and Control Latching Relay

Discussion in 'The Projects Forum' started by abuyaser, Apr 30, 2011.

  1. abuyaser

    Thread Starter New Member

    Apr 20, 2011
    8
    0
    Hello,
    I am responsible for safety in a team project. The prototype is an aquarium light system and my part is to open the main power supply circuit when the prototype falls in water. So, I am using GRI2600T water detector to detect if the existence of water. I am REQUIRED by my professor to use a relay as a switch (I know a GFCI will be the best choice but I am not allowed to use that), I picked up G6BK-1114P-US-DC5 dual coil latching relay which will save the last state it was in even after losing power and I have to reset it if I want to unlatch it.

    Now, I am sending a signal from my GRI2600T water detector to the relay to latch it (5V/56mA), I am considered using pushbuttons to do the job, one normally open and one normally closed pushbuttons but I am not shore how to set up these pushbuttons!!! I guess I need something that can sense the off state of the relay so I can use both of my pushbuttons.

    Please advice on how to set up the pushbuttons and what device do I need to detect the off state.

    Thank you,
    abuyaser
     
  2. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    Your relay is a bad choice for 2 reasons: 1. It is a different voltage than your water sensor. Try to source all your components of the same voltage to simplify your design, not needing several different voltage supplies. 2. The dual coil "state memory" function is not what you want for this application. Your water sensor is a normally closed switch, so you want to detect the absence of voltage. This relay requires the presence of voltage to trigger. Use a normal spring return DPST single coil relay (12V coil) and 2 momentary contact pushbuttons (one normally open and one normally closed) and you can achieve your desired set/reset function. here's how:

    [​IMG]
     
  3. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    I just read your previous post on the same topic and I wanted to clarify that with this circuit, it will never turn on when you plug it in. you will always have to press "set" before it will work. pressing "reset" or detecting water will both result in a reset or "trip" and main power will be cut off.
     
  4. abuyaser

    Thread Starter New Member

    Apr 20, 2011
    8
    0
    I have another sensor that is normally open so I can even have a relay that detects the presence of voltage, one of the requirements is that the switch should remember where it was before losing power
     
  5. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    That is contradictory. If the thing fell in the water and shut off then the "last state" is always going to be "off". Unless I'm missing something. If you really want it to "remember the last state" and still shut down if the thing falls in the water, then trash the relay and the 2 pushbuttons. put the moisture sensor in series with main power and also a regular SPST toggle switch in series with main power.
     
  6. abuyaser

    Thread Starter New Member

    Apr 20, 2011
    8
    0
    OK, I was not clear and misguided you, I apologize


    Here is what I should do: if water is detected I want to shut down the aquarium light system for safety, when water is detected everything should be off including the power supply. Now, this could be accomplished by several ways (GFCI is not allowed in my project), an effective way is to use a relay that will trip either by sending a pulse to it or by the absence of the voltage (either way). I need it to stay tripped until the user resets it manually so the light system can work again in the normal condition where there is no water detected.

    Here are some of the questions regarding this idea:
    1) 1) If I use one coil relay with regular spring, it will do the job and will open up the power supply. However, can the user reset this relay by simply unplugging and plugging the wire into the outlet in the wall?
    If the answer is yes then I need to solve this problem because I want the user to power up the aquarium light system through pushbuttons
    2) 2) Is it better if I get my voltage from the main power supply or should I use my independent battery?
    Thank you for following up with me,
    abuyaser
     
  7. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    If that's what your instructor wants then he doesn't have both oars in the water! Restoring 120V mains power automatically (without human intervention) sounds extremely dangerous. I mean, really... the tank light falls in the water and power is killed. The instant you remove the lamp from the water the power is restored???... That's insane!

    Thank your lucky stars that your course is not "Body Armor Design 101". He would probably have you guys doing live tests. :rolleyes:
     
  8. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    follow post #2, or carefully explain why you can not follow post #2
     
  9. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    This meets your professor's oddball criteria, without any type of relay. Please note that this is not safe or logical way to design this.power will be cut off as soon as the detector sense water, but since you insist on the thing "remembering it's last state" , the main power will be restored as soon as the detector no longer senses water. This will permit you to plug an unplug the thing all day. If you want it to turn off main power and KEEP main power turned off until "set" or "reset" is pushed (i.e. the logical and safe way), then refer back to post #2; Otherwise I implore you to think a little bit harder about what you are asking
    [​IMG]
     
  10. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    please verify the requirements with your instructor before you procede. Also please inform if you still need help.
     
Loading...