Need a alarm circuit built 12volt

Discussion in 'The Projects Forum' started by billkater, Apr 28, 2011.

  1. billkater

    Thread Starter New Member

    Apr 28, 2011
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    Hello all. I am a complete newbie to electronics. But I know what I want can be done. So here is the deal.

    My buddy bales hay. The monitor has a alarm/buzzer on it that will go off when it is time to tie off a bale. The problem is, the buzzer is not loud enough (he is getting hard of hearing) or does it buzz long enough. (only about a 3 second buzz).

    I thought that you could install a light to the system that when activated (jumper off the buzzer) would stay on until manually reset. The system is in a tractor and is a 12volt system. I have not opened up the case so I am not sure about anything else.

    If someone would point me into the right direction and tell me what is needed I am sure that I could come up with something. Attached is a picture of the front of the monitor.


    Thanks for any help you can give in advance.

    Bill

    [​IMG]
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,103
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    Should be do-able. Can you provide more information about the monitor, such as manufacturer and model number? How is it powered? Does it look like you could easily open it up?
     
  3. billkater

    Thread Starter New Member

    Apr 28, 2011
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    I will see if I can get more info in the morning.
     
  4. gerty

    AAC Fanatic!

    Aug 30, 2007
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    Wouldn't hurt to know what type of sensor indicates it's time to tie off.
     
  5. billkater

    Thread Starter New Member

    Apr 28, 2011
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    Ok, I opened up the monitor today. It has a small circuit board inside and the buzzer. It is a: Audiolarm MC-V07-130-Q. The buzzer hooks straight to the circuit board. The board has a connector on it that goes to the baler.

    On the baler there is a micro switch that tells the monitor that it is time to start the bale tying process. The switch is activated by a cam so it is a on and right back off action, about a half a second on.

    The monitor is a New Holland Auto Wrap Model #86624228. The tractor runs on a 12volt system so I would guess this is a 12volt monitor.

    [​IMG]

    How many amps would a set of LED lights pull. Something like a side marker light for a truck.
     
  6. CDRIVE

    Senior Member

    Jul 1, 2008
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    See the attached circuit. I show the input being picked off from across your existing Sonalert. Since it's probably easier to access the micro switch you might consider tapping in there.

    However, we don't know if your microswitch is a high side switch or a low side switch. A high side switch will measure 12V (measured from the chassis) when the contacts are closed. Measured from the chassis, a low side switch will read 0V when closed.

    Note: I drew this before you posted the reference to the microswitch.
     
  7. billkater

    Thread Starter New Member

    Apr 28, 2011
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    would that make a difference if you are getting the signal from the buzzer?
     
  8. CDRIVE

    Senior Member

    Jul 1, 2008
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    My circuit is getting the signal from across your buzzer. That buzzer is more likely a Piezo element with a built in tone oscillator. These can be generically termed a "Sonalert" as indicated in the schematic.

    Bill, now that we know that you have an easily accessible microswitch, can you please answer the questions that I asked in my previous post? The reason that it's important is because my circuit could be simplified greatly with very basic components (Relay and Reset Switch) if you provide the info. We could also loose the wallwart!
     
  9. billkater

    Thread Starter New Member

    Apr 28, 2011
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    Next time I make it to the farm I will check it.
     
  10. billkater

    Thread Starter New Member

    Apr 28, 2011
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    Made it to the farm today. Checked the voltage at the micro switch on the baler. I get 5-volts measured from the switch to the chassis with the switch open. When the switch is closed I get 0-volts.
     
  11. CDRIVE

    Senior Member

    Jul 1, 2008
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    Bill, I have to refresh my memory of what this thread was about. I'll get back to you soon.
     
  12. CDRIVE

    Senior Member

    Jul 1, 2008
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    Bill, do you want the new indicator to stay on as long as the microswitch is closed?
     
  13. billkater

    Thread Starter New Member

    Apr 28, 2011
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    I would like for it to stay on until you manually shut it off or reset it since the micro switch is closed for only a second or so.
     
  14. CDRIVE

    Senior Member

    Jul 1, 2008
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    I drew up two circuits to work off of your microswitch. This is the simplest of the two. Let me know if you have any questions.
     
    Last edited: May 20, 2011
  15. billkater

    Thread Starter New Member

    Apr 28, 2011
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    Does this have a reset switch on it of any type. I dont see one in the diagram.

    Also, I would prefer to just use the signal to the original Sonalert to trip the new light/Sonalert. That way all I would have to do is install a jack of some type in the case of the monitor allowing me to just plug in the new alarm as needed without modifying the wiring in the original monitor. (just pig tailing off the Sonalert leads)
     
  16. CDRIVE

    Senior Member

    Jul 1, 2008
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    Oops, I forgot it! I replaced that schematic with reset added. Refer to that post. I'm also appending a previous schematic that taps into your existing Piezo. I will post it soon.
     
  17. CDRIVE

    Senior Member

    Jul 1, 2008
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    OK, here's an updated (includes parts list) schematic of an earlier post. This circuit is connected across the existing Sonalert.
     
  18. billkater

    Thread Starter New Member

    Apr 28, 2011
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    Looks good. Instead of the single LED could I use a LED light from a trailer. The ones I am looking at has around 10 LEDs in it. What is the max amp draw at the LEDs?
     
  19. CDRIVE

    Senior Member

    Jul 1, 2008
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    I believe the relay I chose in that circuit can handle 2 Amps. Measure your LED trailer light current. I believe the limiting resistor (or active limiter) will be built in. By the way, I like your idea! ;)

    NOTE!! Be careful when placing a multimeter in current (Amps) mode. This is where most people pop things! Start on the highest scale and work your way down for a good reading.
     
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