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need help with latching relay circuit

Discussion in 'General Electronics Discussion' started by the noob, Aug 18, 2012.

  1. the noob

    the noob

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    Aug 18, 2012
    Hey guys, need some help with a project. Im pretty good with 12v electrical wiring but am having trouble figuring this out. Im building a switch panel that i want to use momentary switches to push on/ push off power some 12v accessories like fans and water pumps and have a bi-color led show the status of the accessory(on or off) I was trying to use a pcb that i had lying around as a pcb would save me space but im not familiar with these. My other option was latching relays and plain old wire and connectors.

    Now a friend of mine was helping me but can no longer help. But he was going to have me use an arduino and some 5v latching relays to control the push buttons on the pcb i have already. Now i have the 5v relays but the arduino was his so i dont have it. Maybe someone can draw something up that i could copy. Either for a board or regular wiring. I have room for 5 buttons but only have about 3 accessories to run so the other 2 would be for future expansion if need be. Thanks for any help or direction you can give.
     
  2. Electrobrains

    Electrobrains

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    5
    Jan 2, 2012
    Try to make the diagram yourself and we can look at it!
    Question: Do the latching relays have one or two coils?
     
  3. the noob

    the noob

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    Aug 18, 2012
    Ill try to draw something up and the 5v mini relays are 2 coil. The 12v relay is actually from a Volkswagen and is used as a dimmer for the headlights.
     
  4. the noob

    the noob

    9
    0
    Aug 18, 2012
    2012-08-19_16-07-49_934.jpg

    Heres a quick drawing of the switch panel and the accessories i want to run right now. Its like a fill in the blanks. Lol. One accessory to each push button. The fans are a dual setup so 2 fans is 1 unit. So only 3 buttons will be used for right now but would like to have it setup so if i choose to expand in the future it wont be terribly difficult.

    I have a switch for illumination that i want the led to light green when this switch is on The red side will only light when the accessory is on. The leds i have are 2 lead bi color red/green.


    These are the 5v relays i have

    [​IMG]

    This is the 12v


    [​IMG]

    Let me know what you guys think or if you have a better idea or easier way. Space is somewhat limited to id say about 3" wide x 6"long x 6" deep
     
  5. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    Ok,here are some hints and questions:

    1. You must measure or in another way find out the current of your accessories at 12VDC.
    I am afraid your loads will draw too much current. The shown 5V latching mini relays can (should) only switch maximum 1A @ 12VDC.

    2. How do you want to switch off your fans and pump? All together with one push button (could easily be made with one common push button)? Or each accessory with separate push buttons (2 push buttons/relay)? Or do you intend to toggle the relay state with each pulse you give on the respective push button?

    3. If you intend to use the toggle approach with only one button per load, that will not work well with those Aromat relays. They are normal bi-stable, latching relays and would need additional components to act as sequencing toggle relays. As I understand, the "Headlight Dimmer Relay" is such a toggle relay and could be used with one push button only.

    4. To use the 5V Aromat relays with 12V, you should add a 180 Ohm serial resistor to the coils (coil resistance 125 Ohm). See diagram.

    5. Because you have enough contacts on the relays, the function can be indicated with bi-directional LEDs as seen in the other circuit diagram.
     

    Attached Files:

  6. the noob

    the noob

    9
    0
    Aug 18, 2012
    1. Ill be running 2 16" fans that draw around 18 amps each, the smaller fans are connected and draw about 15 amps, and the pump is rated at 2.3 amps

    2.would like 1 button to turn the accessory on, push the same button again and it shuts off.

    Obviously using the 5v relays will save more space but im more for ease of hook up and use. Just thought id try to do something outside my comfort zone but need help. I got those relays cheap and dont have to use them if need be. But if you guys recommend something else, just give me a parts list of what i need
     
  7. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    One of our members (CocaCola) recently posted an off the shelf kit. It featured a single button, press ON press OFF and a high current FET switching element. You would need one board per circuit though but they're small and inexpensive. If I find the link I'll post it.
     
  8. the noob

    the noob

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    0
    Aug 18, 2012
    Ok. Let me know. Thanks
     
  9. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Here is the link, 10A capacity

    http://www.pololu.com/catalog/product/750


    Great little low cost ready to go solution...
     
  10. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    Well, that settles the matter for the Aromat relays! They are neither suitable with respect to function nor when it comes to the current.

    You would probably need more of those "headlight dimmer relays".
    I don't know the contact rating of that relay, but it looks like a power relay. (If it wouldn't be enough, at least it could be used for driving the pump and other, stronger relays.)

    The suggested "Pololu Pushbutton Power Switch" does not work.
    Firstly, it can not handle 15 or 18A loads and secondly, as far as I understand, it does not have the sequencing toggle function, but seems to work like the normal "2-coil" latching relay (probably without memory function when power removed). It has an on-board push button "on switch" and another "off input". You wouldn't be able to use your bi-directional LEDs in an easy manner either.
     
    Last edited: Aug 21, 2012
  11. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    It can with the addition of a relay, using the module as the latch... Or two modules in parallel if you want to really simplify it...

    The button does not come installed, and the off input is an optional off trigger for the slave device it's not the only way to turn it off... It's operation is push once on, push twice off and so on, unless the off pin is held high then it's off...

    And no it will not remember it's last state if the power is removed, and thus should be hooked to an always on power source if you need it to remember state, using an external relay to do the switching the module can remain on and retain memory while the on/off could also be controlled by a vehicles accessory on/of sequence...

    No more complicated than any other application...
     
    Last edited: Aug 21, 2012
  12. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    CocaCola, thanks for finding my post and saving me having to search for it.


    Chris
     
  13. the noob

    the noob

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    0
    Aug 18, 2012
    If it comes down to it, as far as the led's are concerned, ill use 2 leds( 1 green, 1 red). Thats not a big deal.

    So is there a circuit board setup i could use for this project or just have to use the relays?
     
  14. the noob

    the noob

    9
    0
    Aug 18, 2012
    CocaCola, so how would i use the module to latch? Im looking for something easy but id like to save as much space as possible.
     
  15. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    It latches itself.

    Edit: Btw, did you read the dimensions? It's very small and you don't need to install the header.

    •Dimensions: 0.4" x 0.9" x 0.125" (without header pins and pushbutton installed)
     
    Last edited: Aug 22, 2012
  16. the noob

    the noob

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    Aug 18, 2012
    Yes. The size is good. But would it work with the amps I'll be pushing? Could i make it work?
     
  17. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    With the proper relay the Pololu is easily capable. I was too lazy to draw the Pololu so I just copied and pasted it but it's clear enough for you to see the relay interface.
     

    Attached Files:

  18. the noob

    the noob

    9
    0
    Aug 18, 2012
    Like a standard 12v auto relay and 1 Pololu for each switch would work?
     
  19. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
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    May 8, 2012
    Yes, no problem. Gotta hit the sack.

    Chris
     
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