Two things...hardening homemade circuit and simple delay design

Discussion in 'The Projects Forum' started by Chopski, Jan 17, 2016.

  1. Chopski

    Thread Starter New Member

    Jan 17, 2016
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    Hello.

    I've looked here and on other forums for this but no luck so far. Someone did ask about this in the past when it looks like there was a rule against discussion of automotive projects on the forum but it seems that ban is no longer in effect? Apologies if I'm misunderstood.

    http://forum.allaboutcircuits.com/threads/a-much-needed-delay.104357/#post-791067

    My question is exactly per this older post. That is, I want to be able to activate two different horns on a motorcycle using just one button. Whe th ebutton is first pushed the quieter horn comes on for a fraction of a second followed by the much louder horn if the button is pressed for longer than say a half second. It looks like member k7elp60 has some experience with this application so if he's around maybe he could chime in.

    But I'm also wondering, if I am able to build this circuit, is it practical to use poured epoxy to harden or protect the circuit for an automotive application?

    Thanks.
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
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    I think @k7elp60 is still around, but until he comes:
    When do you want the 2nd horn to shut off? When the button is finally released?
     
  3. wayneh

    Expert

    Sep 9, 2010
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    Hardening seems excessive but is doable. The stuff you want is called potting compound, but you can use cheaper alternatives like fiberglass resin.

    A short delay will be a relatively simple circuit. The current circuit is "direct" with no relay, right?
     
  4. Chopski

    Thread Starter New Member

    Jan 17, 2016
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    Yes exactly. So for short taps on the button you get a small "meep meep" which suffices for most situations where you're letting someone know you are there. Then if you hold the button down the loud horn comes on and stays on until you let the button go.
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Short button tap = quiet horn only. Horn silences when button is released.
    Long button push = quiet horn followed by loud horn. Horn silences when button is released.

    Correct?

    If so, does the quiet horn go off when the loud horn comes on, or are both horns on at the end of a long button push?

    EDIT: answered while I was typing...

    Is the switch pulling the control signal up to 12 V or down to GND?
    Assuming the quiet horn is controlled by a relay, is the horn switched to 12 V or to GND?
    Does the loud horn have to be switched by a relay, or are you open to a power MOSFET?
    What is the current drawn by the loud horn?

    ak
     
    Last edited: Jan 17, 2016
  6. Chopski

    Thread Starter New Member

    Jan 17, 2016
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    Correct except...I was thinking about whether the quiet horn turns off when the loud horn comes on and maybe it doesn't matter. There are two options:
    A) as soon as the horn button is pushed the small horn sounds and a delay starts counting down. If the button is still depressed when the delay hits zero then the loud horn comes on too.

    If that's easier then that's fine by me.The other option is as you mentioned where

    B) as soon as the loud horn comes on the quieter horn is turned off.

    Is the switch pulling the control signal up to 12 V or down to GND? Not sure what you mean by this. It's for a motorcycle with -ve ground if that helps. Otherwise what do I need to check to answer?

    Assuming the quiet horn is controlled by a relay, is the horn switched to 12 V or to GND? Again sorry not sure. I'm more of a mechanical guy than electronics..

    Does the loud horn have to be switched by a relay, or are you open to a power MOSFET? The loud horn comes with a relay. Does that make a relay the best or easiest way to go? If a MOSFET isn't beyond the budget I'm OK with it.

    What is the current drawn by the loud horn? 18A or less.
     
  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    If the horn comes with a relay, then all we need is the relay coil resistance. Is there a wiring diagram for the bike?

    ak
     
  8. Chopski

    Thread Starter New Member

    Jan 17, 2016
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  9. wayneh

    Expert

    Sep 9, 2010
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    Yes, that's very believable. That means it would draw about 14V/88Ω=0.16A or 160mA.
    There's not enough resolution to see anything. Perhaps you could break it into smaller chunks and maybe just focus on the horn components.
     
  10. Chopski

    Thread Starter New Member

    Jan 17, 2016
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    Ok maybe this PDF will work better. The horn is shown in the bottom right hand corner to the left of the list of fuses.
     
  11. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    A simple 555 monostable with change over relay will do this, the horn is positive pulsed.
     
  12. Chopski

    Thread Starter New Member

    Jan 17, 2016
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    Ok I'm going to try to parse that for my non-electronics oriented brain. :)

    So:

    1. Horn button is pressed which closes circuit to small horn AND 555 monostable.
    2. This triggers small horn to come on and 555 to start counting.
    3. When the 555 reaches the set time interval the changeover relay opens the circuit to the small horn and closes the circuit to the big horn.
    4. Big horn only sounds and SUV driver moving into my lane right on top of me doesn't smuck me into oncoming traffic.

    Do I have that right?
     
  13. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Correct, big horn stays on after little horn, and only stops when you release the button.

    parp parp, AROOOOGA!!!
     
  14. Chopski

    Thread Starter New Member

    Jan 17, 2016
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    Excellent. In Canada we would pronounce that, "Meep meep. BRAAAPPP!!!"

    So besides the two obvious components we've already discussed, what else is required? Diodes? Dilithium crystals?

    And is it practical to pour some epoxy all around this thing once it's built to protect against moisture and vibration?
     
  15. wayneh

    Expert

    Sep 9, 2010
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    I think you could also get away with a simple RC delay timer such as the simplest one discussed here. (There are many other based on the same principle - it takes time to charge a capacitor to a voltage high enough to turn on a transistor that allows current through your relay coil.) You don't need precise timing, just a brief delay. The 555 is a fine solution also, but maybe a bit of overkill for this application.
     
  16. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Here. You can put the circuit between the switch and the horn (then horn connects to chassis ground), then need to put one jumper from this circuit to ground.

    The potentiometer lets you adjust the delay from 0.1" to about a second.

    image.jpg
     
  17. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    GopherT likes this.
  18. Chopski

    Thread Starter New Member

    Jan 17, 2016
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    Very nice. Thanks fellas. You folks don't mess around on this forum. Just get right down to it.

    Now as far as the practical aspects, again I'm wondering if anyone can advise on the practicality of hardening the circuit against weather and vibration by pouring on the epoxy. Anyone have experience with this?

    Any other tips on how to execute this? Just grab a regular circuit board and start soldering on the bits?
     
  19. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Build it on a strip board or perf board. Test it for a day or two. Get a small project box or plastic mentos box fill it with epoxy. You will need a lot of epoxy. The hobby stores with RC airplanes in your area is likely the best (and cheapest) place to buy 2 to 4 oz tubes of epoxy and hardener. You can also use "metal safe" silicone. This is cured without the odor of acetic acid and safer for the circuit. Others may be fine but since it is available, you can use it.

    Use good quality wire (same or thicker than what is on the bike horn already). Should be flexible, stranded, not solid wire.

    As for not fooling around, I am surprises we waited until post 15 or more.
     
  20. ISB123

    Well-Known Member

    May 21, 2014
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    He could try silicone tile adhesive.
     
    GopherT likes this.
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