Need a little help please

Discussion in 'General Electronics Chat' started by rootuser, Mar 23, 2009.

  1. rootuser

    Thread Starter New Member

    Mar 22, 2009
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    Hello all,

    I am designing a children's game, and I have almost everything working, however, I am stuck on one part (this is entirely an analog set up)

    What I want to do is create a section where if you unplug the wrong wire from a quick connector (single wire) a piezo buzzer goes off. Thus if you cut the circuit, the buzzer sounds letting you know you made a mistake and then if you plug it back it in, the buzzer shuts off.

    I'm not really sure where to start on this one so any help would be appreciated.

    Thank you in advance.
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,344
    Hello,

    Where does the other end of the wire go ?
    Can you make a drawing of you idea ?

    Greetings,
    Bertus
     
  3. recca02

    Senior Member

    Apr 2, 2007
    1,211
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    A Relay might be help.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,638
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    Hello,

    Some more questions.
    How many leads are there ?
    Does every (if more than one) needs to be in a special place ?

    Greetings,
    Bertus
     
  5. PRS

    Well-Known Member

    Aug 24, 2008
    989
    35
    Try using a 2-input AND gate with one input connected to 5 Volts and the output driving a buzzer that has one end already connected to ground. The other input is connected to ground but there is a pull up resister to 5 volts right at the gate input. Then disconnecting that wire will bring both inputs to 5 volts and the alarm goes off until you put the wire back.

    Incidently, what are you making? Sounds like a bomb diffusion game ! :)
     
  6. rootuser

    Thread Starter New Member

    Mar 22, 2009
    4
    0
    Thanks for the ideas.

    Unfortunately I don't have a drawing because I am not quite sure how to do it!

    As for what I am building it is kind of like a bomb defusion game kinda, but in this case you are trying to stop a run away train, and you are changing track switches etc. The buzzer is actually a faux "collision alarm". Its kind of a puzzle. Hard to explain without giving away too much. I am just trying to build a fully working prototype at this point.

    To make it more clear, I have a 9-volt circuit (could be change to anything from 3V to 15V, doesn't matter it's a seperate circuit)d and all this circuit needs to do is sound an alarm if you unplug the wrong wire. If you unplug the correct one, the red collision light shuts off and you go to the next part of the game.

    To answer some of the questions asked:

    Under to covers this is all plugged in to a Euro-block so I can re-arrange as needed.

    Right now there will only be 3 connections. 1 that does nothing, 1 that turns on the buzzer when unplugged and the other that turns off the red light when unplugged. It's really simple at this point. The plan is to get more complex, however I'm stuck at this point so I don't want to venture more in to it until I understand more.


    Can you please elaborate on the 2-input AND gate idea? I'm not sure I really understand the gate portion (yes it's a diode but can you explain further). I did think about a pull up resister or capacitor of some type that would dump charge when the line is disconnected, however I am just not understanding how to make it work, or even exactly what parts I will need.

    I am an engineer so you'd think I'd have a grip on this but apparently I have hit a complete mental block. Any further elaboration spelt out for my newbieness would be great.

    Thanks so much.
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,344
    Hello,

    There are three connections.
    Are all connections plugs with wires ?
    Can the plugs be placed at other connections ?
    You could use three wires with different voltages.
    On the connections there can be window comparators.

    Greetings,
    Bertus
     
  8. PRS

    Well-Known Member

    Aug 24, 2008
    989
    35
    rootuser, I'd like to draw a circuit, but I have no way to do that. I can, however, point you to an invaluable source that will get you thinking more clearly on what it is you need to buy and utilize:

    Getting Started in Electornics by Forest Mimms III. It's an easy-to-read and understand guide for beginners. It's full of circuits that show you how to make the kind of thing you're doing. Cost me 2.5 dollars at Radio Shack. Can't say how much it cost now; this one is quite old, but Radio Shack still stocks them.

    Your need is a very simple logic problem easily solved with off the shelf stuff you can get at Radio Shack. I'm not a representative for RS, don't like to buy from them, but for beginners they're a good place to start. Perhaps someone else in this forum who has the means can draw you a circuit will do so. Good luck.
     
  9. rootuser

    Thread Starter New Member

    Mar 22, 2009
    4
    0
    Thanks for the input. I think at this point I have a direction to head in terms of the AND gate with the two inputs. I can explore that further but it makes sense. Thank you for the help thus far.

    Right now, the connections are all unique and cannot be switched between each other, although that may change.
     
  10. PRS

    Well-Known Member

    Aug 24, 2008
    989
    35
    rootuser, if the AND gate makes sense, you must have a familiarity with logic gates. I'm intrigued by your game design. I wanted to make a better CLUE game and I wrote a computer program to do so, but I had no experience in graphics and let it go. This was about 10 years ago. It's all about graphics with computer games these days.

    At any rate, I'll help you in any way I can. If you use TTL gates -- the 74xx family -- just knock down the 9 volts to 5 volts with a zener diode. Otherwise use CMOS.

    But, again, here is the idea. With an AND gate the output goes high (turning on your buzzer) only when both inputs are high. Just connect one input to high (5V) and the other (the wire that has to stay connected else alarm sounds) to ground, but right at the input of the gate (where pulling the wire away wont be of any significance) put a pull up resistor (1K?). So when the wire is pulled away, that input to the gate goes up to 5 volts and the alarm goes off.

    If you're familiar with basic logic gates you should be able to work out the details of further elaborations. Hope this helped. :)
     
  11. rootuser

    Thread Starter New Member

    Mar 22, 2009
    4
    0
    I think I get it, I am vaguely familiar with the TI 7400 but it's been years and years, I'll have to give myself a refresher course.

    I'll probably look to stick with the TTL unless there is a compelling reason to use CMOS.

    According to what you said:

    With an AND gate the output goes high (turning on your buzzer) only when both inputs are high. -- Makes sense. So for example let's say Pins 4 and 5. That means Pin 6 is for the output and goes to the buzzer and will sound if the output goes high pushing 5 volts. Unless pins 4 and 5 both get +5 volts, the output will remain at 0.

    Just connect one input to high (5V) -- A wire that cannot be unplugged, this will be a constant 5V. Let's say Pin 4.

    and the other (the wire that has to stay connected else alarm sounds) to ground, but right at the input of the gate (where pulling the wire away wont be of any significance) -- Here is where I am lost. You said right at the input of the gate, so in our example do you mean at pin 5? And I assume the other end goes to ground (usually pin 7 I think).

    put a pull up resistor (1K?). So when the wire is pulled away, that input to the gate goes up to 5 volts and the alarm goes off -- Understood here I think, both pins 4 and 5 would have +5 volts and thus sound the buzzer. Pin 4 has a constant 5V and if the other wire is unplugged the pull up resistor will try to make up the loss and output 5V to pin 5 causing the voltage to flow out of pin 6 (sounding the buzzer).

    Am I on track here?
     
    Last edited: Mar 23, 2009
  12. PRS

    Well-Known Member

    Aug 24, 2008
    989
    35
    You've got it. And, yes, put the pull-up resistor between pin 5 and 5 volts. The pull away wire is connected to ground at one end and pin 5 at the other end. Pulling away either end will turn the gate on.

    It's too bad that someone with the software didn't give you a diagram. Perhaps someone will.
     
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