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Voltage help?

Discussion in 'General Electronics Discussion' started by 13th_Doctor, Jun 15, 2013.

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  1. 13th_Doctor

    13th_Doctor

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    Jun 15, 2013
    I'm modifying an alarm clock with a louder alarm I found, but the alarm takes 9v, and the clock runs on 3v. Any Ideas on how I can make this work?
     
  2. grim_reaper

    grim_reaper

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    Jun 15, 2013
    You'll need some kind of relay system. In order to drive the louder alarm, it needs the higher voltage supply, and to control it you need to interface to it using a relay or similar arrangement.
    Someone with more expertise might be able to suggest a way to push the 3v supply up to 9v, but I'm guessing it would be more trouble than it's worth.
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Generally speaking, the 3V alarm signal can turn on a transistor which then turns on 9V to the new alarm.

    It may not be that easy though. We'd need more details.

    Like... Does the alarm signal just turn on, or is it an AC signal for driving a transducer (for example)
     
  4. 13th_Doctor

    13th_Doctor

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    Jun 15, 2013
    The whole thing is DC, when the alarm turns on it's just switched on.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Then, dear Whovian, all you need is to use this voltage (via a 1k resistor perhaps) into the base of an NPN transistor like a BC548 with it's emitter tied to the 0V of the clock and your 9V source. The new load is placed between the +9V and the collector of the transistor.

    This assumes that the output is at 0V and rises to 3V when the alarm is going off.
     
  6. 13th_Doctor

    13th_Doctor

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    Jun 15, 2013
    Thanks!! It's working. My days of oversleeping are done with.
     
  7. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Ever wonder why we say that? I mean most of us do, even with oceans separating us. ;)
    I don't think I've ever heard a person say "Then the alarm went on". :D
    Chris
     
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