Power failure warning with reset simple circuit help

Discussion in 'The Projects Forum' started by griffin Dahlberg, Mar 5, 2015.

  1. griffin Dahlberg

    Thread Starter New Member

    Feb 25, 2015
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    2
    Hi,
    I have been working on a project that needs to simulate a power failure by flipping a switch and then turning on a led that uses a second battery, even after the power turns back on, via the switch, the led should remain lit until a reset or acknowledge button has been pressed. here are the details:

    Lab Project:
    Design a failure/reset operation for DC power failure.
    Required components:
    · Multiple power supply feeds/output
    · Switches
    · Resistor(s) as needed.
    · LEDs to indicate operation/failure status—Tristate diodes are permissible
    · Other components as you see fit.
    Project Operation:
    Design a circuit such that when one power supply (Vs]) for a particular circuit fails, an LED will turn on, indicating that main power has failed. This LED should remain illuminated even after Vsi powers the circuit again, until an "Acknowledge" button has been pressed to reset the LED. Be mindful of components that must be used in conjunction with LEDs.​

    I have designed a multisim file with two leds and a relay but the two leds are not working with a switch so any help either with two leds or one on designing this circuit would be appreciated, I have attached the multisim file below.

    Thanks,

    I will check back later
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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  3. #12

    Expert

    Nov 30, 2010
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    Actually, he does need the reset button. It is a requirement of the job to demand human intervention.

    You need to use a reset switch to activate a latching relay that keeps the LED off. When the primary power to the latch fails, the relay falls unenergized to the fault condition.

    Is that enough of a hint for your homework problem?
     
  4. griffin Dahlberg

    Thread Starter New Member

    Feb 25, 2015
    12
    2
    No, the button is used to be a means to say that you have acknowledged the fact that your power went out and controls the second circuit of the relays led. this led should remain on even after the power switch for main power is turned on again and go out after this acknowledge button has been pressed
     
  5. griffin Dahlberg

    Thread Starter New Member

    Feb 25, 2015
    12
    2
    I have been looking at latching relays and I could not for the life of me get one working in multisim because they do not have a means of hooking up a dpdt relay switch component. I just need to get a parts list. I was going to use a dc power supply in my lab at school and have that at 12v and use a battery pack for my light to illuminate once the switch to the power supply is turned off, but again, this light should remain illuminated until a reset button is pressed. From the research I have been doing the last 3 days, I cannot seem to piece together such complicated schematics that I find for latching relays, also, with the latching relay I have been having a hard time thinking about where to connect the 2 power sources. This is an intro class so this means he doesnt expect any digital components as this is out of my current expected knowledge.
     
  6. #12

    Expert

    Nov 30, 2010
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    You don't, "find" a latching relay, you build a latching circuit with a double pole relay. One wiper controls a power feed to the coil and one wiper feeds power to the LED. After you're done with the first design, you might see how to use a single pole relay with the wiper either feeding its own coil or the notification LED.

    My personal opinion is: Quit depending on a friggin' simulator to dictate the limits of your mind. They are still in their infancy and sometimes, they are simply wrong.
     
    RodneyB likes this.
  7. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    As I undeerstand it, the sequence of events is as follows
    1. Power has been applied - a relay is activated [initial conditions]
    2. Power is lost - relay is deactivated AND LED turns on [perhaps by a second relay?]
    3. Power returns - relay is activated AND LED remains lit
    4. An acknowledge pushbutton is pressed and the LED goes out
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
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    There are two types/methods for latching relays, the first is to use a latching contact on the relay itself, the other is magnetic latch/unlatch types.
    The first drops out with power loss, the second stays retained (memory) in the absence of power.
    Max.
     
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  9. griffin Dahlberg

    Thread Starter New Member

    Feb 25, 2015
    12
    2
    I was trying to figure out what components I needed so that I could order them as they were supposed to be ordered as of yesterday, although I couldnt get it to work in multisim so I postponed it, what components would
    Yes, This is exactly it. I am not too experienced with any of this stuff and I just figured that I could use multisim which was required by my professor to do the testing to justify him buying the components so it is kind of a crappy situation
     
  10. griffin Dahlberg

    Thread Starter New Member

    Feb 25, 2015
    12
    2
    Thank you everybody for your input, it does not go without recognition.

    Much obliged
     
    Reloadron and #12 like this.
  11. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    If that is "it" then the second relay is unnecessary.

    All a latching relay is is this: imagine a relay you turn on by pressing a button. Release the button and the relay goes off.

    Now put a normally open relay contact across the button. You press the button, it turns the relay ON, you release the button and the relay contact keeps the same relay ON.

    Loose power, the relay goes off. Power comes back, the relay stays off until you press that magical button called “acknowledge”.

    You control the LED thru the second set of normally closed contacts on this relay (why I said DPDT).

    Relay turns off, LED turns ON.
     
    griffin Dahlberg and #12 like this.
  12. griffin Dahlberg

    Thread Starter New Member

    Feb 25, 2015
    12
    2
    Hey, What would the circuit need to look like to implement a primary power source with a secondary battery? this is my last problem,
    Thanks
    Griff
     
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