Changings Polarity for a 2 color Momentry Button's LED Color

Discussion in 'General Electronics Chat' started by MrSmoofy, Jul 28, 2014.

  1. MrSmoofy

    Thread Starter Member

    Jul 28, 2014
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    Backgrounds: I'm completly new to electronics so be gental. I've been a softwre developer for 20 years.

    Project: I'm making a fireworks lauching control box.

    Question: I have sourced some momentary buttons from china that light up red or green depending on the polarity.

    What I'm attempting to do is have the button light up green when unarmed and red when armed.

    Lighting up at all means that the "Test current" across the e-match is there (good connection) and when the Key switch is in unarmed the button would light green (when the power switch is on). When the power switch is turned to armed the buttons that had a good connection would turn red (polrity reversed) and can be fired.

    Since I'm a completly newbie I'm not sure how I would go about switching polrity to the buttons when the key is moved from armed in a safe way so that there is not a moment where both sides of the LED button connectors are both + or both - at teh same time during it's transition.

    Thanks for your help.
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    This sounds like an entry for a Darwin Award competition ;). Given your admitted lack of electronics skills and the potential hazards of fireworks it would be better to leave this to a skilled person. There are plenty of safer electronics projects to cut your teeth on and which we could suggest/ give advice on.
     
  3. MrSmoofy

    Thread Starter Member

    Jul 28, 2014
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    Thanks for not providing any usefull answers to my question I really appreciate it. I can understand your concern for my well being as a completly stranger and assure you that I will not shoot my eye out.
     
  4. inwo

    Well-Known Member

    Nov 7, 2013
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    More information about the switches you have might inspire more confidence in your ability.

    I've noticed that this site has high interest in safety.

    Is the mom. switch a 4 terminal device? 2 for N.O. switch and two for the indicator?

    Is the key switch-multi pole or just a single pole needing a relay for logic?
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Useful answers require more information from you first.
    What is the contact arrangement (poles/throws) of the keyswitch?
    What is the full spec (voltage/current rating) of the momentary buttons?
    Is the 'power switch' the same thing as the 'keyswitch'?
    It might also be useful to know:-
    What voltage/current rating does the power supply for the control box have?
    What circuit do you propose to use for the test current?
    Will several e-matches be fired simultaneously?
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    MrSmoofy, welcome to AAC.

    This site promotes free educational advice in the safe pursuit of all things electrical and electronic with some exceptions. Read the advice posted and learn to be humble and grateful.

    Also make sure you read the Terms of Service (TOS) found at the bottom of the page.
     
  7. MrSmoofy

    Thread Starter Member

    Jul 28, 2014
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    First off I am humble and grateful to anyone that helps. Sorry if I came off rude it was my intent. If you need more information you'll need to ask me questions and I'll provide more details I was not sure what details or how would be needed to answer my question about the switching of the polarity with the key switch. What I don't want to happen though is I give you all the details and you basically do it for me. I want to understand learn along the way as I have other projects I want to try and do. I've done the MakerShed Make Electronics projects from the first book and am working on getting the second book that came out a month before last to do those projects as well. I understand I'm likely to burn/blow things up in the process but that's part of learning. I will not be connecting any e-matches or fireworks unless outside and at a safe distance.

    This is the button: http://www.aliexpress.com/snapshot/6149634066.html

    Is the mom. switch a 4 terminal device? 2 for N.O. switch and two for the indicator?

    -- Yes

    Is the key switch-multi pole or just a single pole needing a relay for logic?

    -- Have not purchased this yet. Basically as I understand different parts I buy what I think I need and then experiment with that component to fully understand it.

    What is the contact arrangement (poles/throws) of the keyswitch?
    -- See above link to button. 2 contacts for red/green color by reversing polarity. 2 contacts for mom. button

    What is the full spec (voltage/current rating) of the momentary buttons?
    -- See above link. I planned on a 12v system (might be overkill) so they sent the button (sample) with a resister already soldered.

    Is the 'power switch' the same thing as the 'keyswitch'?
    -- No I intend to have a main power switch as well (rocker switch) that controls power to the whole panel. The key switch would be to switch from the current for making sure the e-matches are connected (GREEN on buttons) and when the key is switched the buttons would show red indicating armed. Pressing the button would send the ignite current.

    What voltage/current rating does the power supply for the control box have?
    -- I thought 12v (I don't know why) but wanted to be able to use a rechargable battery on the fence if it's removable to be charged or has a charging port. 12v might be way to much it was just a number I picked out of the air and am open to suggestions.

    What circuit do you propose to use for the test current?
    -- Not sure how to answer this. The button in the Unarmed key state would be dead and do nothing only light green when an e-match is connected correctly and the main power switch is on. In the Armed key state the button would be red and the button press would send the fire current.
    The e-matches have the following: Fire current: .37A Test Current 0.5MA

    Will several e-matches be fired simultaneously?
    -- For Rev 1 I planned on each button to only fire 1 e-match (each e-match could fire more then 1 firework)

    Let me know what other info would be needed.

    I'm thinking for the polarity change the key switch would be double throw double pole or might need more poles to allow for the higher Armed/fire current to be switched on off with the key and not affect that with the polarity being switched.

    Something I did learn this weekend as I was experimenting with my new mom. LED button was that my meter (Fluke 87v) continuity test puts out enough current to illuminate the LED. Probably something I should of realized but now I'm curious how much current it actually puts out my guess wold be very little.
     
  8. inwo

    Well-Known Member

    Nov 7, 2013
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    Doodled this before reading last post.

    I have no idea what safety requirements are.:eek:
    Such as testing for open mom. before arming. (key)
     
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  9. MrSmoofy

    Thread Starter Member

    Jul 28, 2014
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    Thanks what you have there is kind of what I thought needed to happen. You bring up a good point though testing for open mom before arming that's probably a good idea incase a mom has failed or is stuck open.
     
  10. inwo

    Well-Known Member

    Nov 7, 2013
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    If mom. had a N.C. contact, it could be in series with led.

    That way there would be no "ready" light if button was stuck. However it would still fire when armed.:(

    Is more logic needed to "lock out" arm system if not safe? Else it could fire on key switch if button was held in.

    Don't have answers but the dialog should get you where you want to be.:)
     
  11. MrChips

    Moderator

    Oct 2, 2009
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    I would suggest that you use separate LEDs instead of a single bi-coloured LED. It makes life easier.
     
  12. MrSmoofy

    Thread Starter Member

    Jul 28, 2014
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    Since I'm not lighting candles and will be lighting fireworks it seems that a lock out when switched to armed if any buttons show open would be the best way to go. Thanks for bringing this up it was not something I had thought about yet but seems like a good safetly feature to have.
     
  13. MrChips

    Moderator

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    Looks to me like this should work.
     
  14. inwo

    Well-Known Member

    Nov 7, 2013
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    Without re-drawing.
    Change switch to relay.
    More doodling.

    Lockout relay won't pull in unless button is ok.

    Requires N.O./N.C. button though.

    Oops forgot key.
     
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  15. MrChips

    Moderator

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    This is maybe how I would approach it:

    [​IMG]
     
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  16. MrSmoofy

    Thread Starter Member

    Jul 28, 2014
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    Thanks MrChips for showing me the option with using seperate LED's vs the dual color LED button.
     
  17. MrSmoofy

    Thread Starter Member

    Jul 28, 2014
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    This is awesome thanks. Everything is clear except the NO/NC button and how it's different the momentary button I have. Quick google suggests it's not momentary anymore and is more of a latching button? 2 posts are for the LED 2 posts are the the button that is open and then is closed when pressed.
     
  18. inwo

    Well-Known Member

    Nov 7, 2013
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    Still momentary. When one opens the other closes.

    I'll try to think of something using just the normally open, if that is what you have.
     
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  19. MrSmoofy

    Thread Starter Member

    Jul 28, 2014
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    Ahh I understand now. So if it's closed (button pressed, broken, etc) while in Unarmed a relay is controled to not allow power when switched to armed if I'm understanding correctly. So would you turn off that relay when armed so that whne the button is pressed it doesn't activate that relay and kill the power to the other armed buttons?

    Right now I just have 1 button I've not ordered any others (except for some other samples that have be lost by DHL) as I wanted to just try them out before I settled and ordered any. I will have to check with where I got the one button from to see if they can supply a NO/NC button or if I can find any like the one I have which I really like.
     
  20. inwo

    Well-Known Member

    Nov 7, 2013
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    I hadn't thought it out further than one unit.:)

    There is no reason that all the fire buttons couldn't have their N.C. button contacts in series.

    If all buttons were safe, (closed circuit) relay would latch through CR1 contact across all buttons. Pulling in "arm" (CR1) relay. Until such time as key was turned off. (reset)

    I haven't found a good button for you. Nor have I come up with a simple "switch check" not using a special button.:(

    edit:
    Of course each button could use a contact expanding relay. But then we're on a road far away from KISS!
    And a solid state logic solution would look good.
     
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