How can I replace a watch alarm with a motor?

Discussion in 'The Projects Forum' started by JC531, Dec 28, 2014.

  1. JC531

    Thread Starter New Member

    Dec 28, 2014
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    Hey guys! New member to AAC. Currently I am working on a project for my application to WPI in Worcester where I am discussing a project and plan for a vibrating watch for use during tests.

    Because I can only currently keep the experiment for the watch as a prospective one, I decided that I should also supply a base design and ideas for how to make a simple prototype.

    The goal right now, how would I replace the alarm of a watch with a vibration motor? I get that it probably wouldn't fit that's why its only for prototype testing purposes. But the issue comes with the fact that this must be more complicated than just wiring positives and negatives.

    Say the speaker does work off positive and negative leads, if the motor requires more power than those two leads can supply how could I make sure it gets it? Would something like an external power source (battery) be in place for that part of the circuit? Is that possible?

    I'm an absolute noob with circuitry (I shouldn't be with the number of projects I've done) but I don't know how to plan a circuit and whatnot. Lol I haven't gotten there in AP Physics yet!

    Thanks in advance AAC!
     
  2. blocco a spirale

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    Jun 18, 2008
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    You should first ask yourself;

    a)What type of signal is driving the speaker?
    b)What type of signal does the motor require?
     
  3. JC531

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    Dec 28, 2014
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    What do you mean by signal?

    (Apologies in advance for my inexperience)

    Do you mean how they are powered? If so, the watch I have been looking inside of has a speaker (cannister/motor looking thing) that is connected to two leads. The vibration motors I used to have also were like this.
     
  4. blocco a spirale

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    Yes, what type of signal i.e what is driving them exactly? i.e. voltage, current, frequency....
     
  5. JC531

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    Dec 28, 2014
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    Ah, I see. That, I do not know. Currently I guess you could say the design is a little abstract in a sense due to not having a functional motor with me and the watch itself ceased function (I had it out open for a while and I'm guessing this led to the alarm not going off ever again. It has been about a month give or take that it was disassembled).
     
  6. blocco a spirale

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    Well, you gotta know these things in order to interface the two. However, even at this stage it is possible to make certain assumptions about what types of signals are involved.
     
  7. JC531

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    Dec 28, 2014
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    Awesome. How so?

    Thanks again by the way!
     
  8. blocco a spirale

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    This comes back to the questions in #2.

    What do you think?
     
  9. blocco a spirale

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    Just help out;

    What type of signal does the speaker require AC or DC? What sort of voltage is likely to be available? What sort of current is it likely to be available?

    What type of drive does the motor require AC or DC? What voltage is it likely to be? What sort of current is it likely to require?
     
  10. JC531

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    Dec 28, 2014
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    Hmm, well. I would say DC for both knowing that AC is (to my knowledge) used for power plants and DC due to sending power directly to one place. In terms of voltage, I would say it would have to be less than 5v assuming a usb amount of power to be to large for the seemingly simple processes of the watch. As for the motor, yes DC due to the instant current being what activates it. Also less than 5v for the motor, surely a small motor such as one in a smartphone would not use that much power.
     
  11. MikeML

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    Almost certainly, the watch is not using a "speaker". More likely, it is using a piezo sounder:
    [​IMG]

    Also, the watch electronics generates a square-wave drive signal of about 2-3KHz. You need an Oscilloscope to find out.
     
  12. blocco a spirale

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    So, you're saying that the speaker/ piezo sounder (thanks Mike) requires DC? Does this make sense to you? What does DC sound like?
     
  13. JC531

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    Dec 28, 2014
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    Yes, DC makes sense, especially since the current would only go to the sounder, I don't see why it would need to send energy in reverse (as I believe AC to do). And since there is only one tone that is played from the alarm, DC's sound would be the same wouldn't it? In terms of like a signal on/off that gives it its "tune" (the set of beeps).
     
  14. blocco a spirale

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    Generally speaking; in electronics, DC voltage is an unmodulated constant value, it does not change. Any signal that is modulated in any way, regardless of whether it switches polarity, is usually considered AC. You can also have a mixture of both. To drive a sounder you require AC.
     
  15. JC531

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    Dec 28, 2014
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    Ahh. Ok. This is so cool!

    So then, the sounder is AC, and the motor, would that be AC as well? Since it's speed could be changed? The speed change being a result if change in...voltage?
     
  16. MrChips

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    DC and AC. Boy, you have a lot to learn yet. Don't take this personally. Welcome to AAC! Stick around. Read the tutorials on AAC and ask a lot of questions. You'll get it right eventually.
     
  17. JC531

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    Dec 28, 2014
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    Lol, I won't. Hahaha thank you!
     
  18. MrChips

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    So let's get a few things straight.

    1) The comments made in the previous posts are right on track. You need to know the type of signal, AC or DC, voltage and current for the devices in question.

    2) AC is not just for sending energy from power plants. AC and DC are not restricted to any given application. There are AC power lines and there are DC power lines.
    There are AC motors and there are DC motors. There are AC transducers and there are DC transducers.

    AC is sometimes considered as a reversal of voltage or current but does not have to be. ON and OFF DC is also considered AC.

    3) Know your current and voltage specifications and limitations. What battery is in the wristwatch? What is the voltage? How much instantaneous and average current can it supply? What is the voltage and current requirement of the transducer? What is the voltage and current requirement of the motor you wish to drive instead of the transducer?

    So, electronics is not simply connecting one component to another. Electronics is an engineering discipline. You have to the climb the knowledge curve before you can call yourself an electronics engineer or specialist.
     
  19. MikeML

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    No, not DC. I say again: "Also, the watch electronics generates a square-wave drive signal of about 2-3KHz. You need an Oscilloscope to find out."
     
  20. MrChips

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    I was going to get to that. Just waiting for the TS to respond.
     
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