3 month countdown alarm (miniature circuit)

Discussion in 'Homework Help' started by MLD, Jul 9, 2015.

  1. MLD

    Thread Starter Member

    Dec 7, 2012
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    Hello Everyone,

    Im trying to build a 3 month countdown timer alarm in the smallest miniature form there possibly is using the smallest electronic components. Trying to use the smallest battery like a watch battery or smaller, I would like the timer countdown to start right after I apply power to the battery then sound a buzzer after the countdown has been completed. Id like the buzzer to be the smallest and very low consumption.

    If anyone can help me supply me a schematic diagram and the parts list it would be great that way I can go ahead and build it and test it.

    Thank You All.
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    OR, you could supply me with a block diagram and schematic of what you have so far, tell me if this can use a microcontroller or must be all discrete hardware, information about what accuracy you need, the type of display, any switches or controls, how the device will be packaged, what environment it will be used in, and basically everything I need to do all of the work for you.

    Based on your description, a PIC10F200T-I/OT will do this for 42 cents.

    ak
     
    Last edited: Jul 9, 2015
    Roderick Young likes this.
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    How do you propose to set the time period?
    Does it need to be adjustable?
     
  4. DickCappels

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    Aug 21, 2008
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    A long time ago I read an application note for this very thing. It was a timer to indicate when it is time to replace air filters in office buildings. The solution presented in the application note was a microcontroller with on-chip clock generator.
     
  5. AnalogKid

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    The PIC has an internal clock oscillator factory trimmed to 1%, so the period might be 89 or 91 days. For another 10 cents there's one with1/3 the operating current for even longer battery life. Scarey what you can get in a SOT-5 package. Is my memory conflating things or does someone make a 3-pin uC?

    ak
     
  6. MLD

    Thread Starter Member

    Dec 7, 2012
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    3 months is the time of the countdown. Not adjustable. Does not have to be exactly precise at 3 months but close. As small as miniature as possible. No switches, no displays. Simplicity. Smallest and most economical as possible. It will be at room temperature and normal atmosphere. It will not be exposed to rain or humidity.
     
  7. AnalogKid

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    BOM: Battery, decoupling cap, PIC, beeper.
    Have two of the PIC output drive a piezo beeper and there's nothing left to do but the firmware.

    ak
     
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  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    As I'm stuck in the past, I would use 2 SMT 4060's, buzzer driver, & a few R's & a C. First 4060, stage counts up to 24 hours, 2'nd counts to 2048, but to avoid decoding, tweek colck to give 2160 hours @ 12 th stage, which on resetting causes 13 th stage to go high, turning on buzzer. What turns buzzer off?? Guessing about 40 mA hr. for battery, excluding buzzer.
     
  9. Dodgydave

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    Jun 22, 2012
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    Here is a programme using a pic12f675 for three months, sets two outputs to go complimentary after time limit , then stops, use it to feed your buzzer.

    the pic is a 8 pin dil, works from 3-5V dc, i am sure you can modify it for other smaller pics if you want.
     
    Last edited: Jul 10, 2015
  10. AnalogKid

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    My first thoughts also. But some jobs cry out for a uC, and a 38 bit counter plus a beeper seemed to be one of them.

    ak
     
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  11. MLD

    Thread Starter Member

    Dec 7, 2012
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    AK, what will be the smallest parts to use PIC, CAP, BATTERY, BUZZER I usually buy my parts at digikey, can you supply me with a parts list from digikey? Can you provide me with the schematic diagram and the firmware, id like to build this and test it by the end of this month. THANKS
     
  12. MLD

    Thread Starter Member

    Dec 7, 2012
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    Dave,

    I have either the Top Max II or the Chip Max II programmer by EE tools, I have to check which is the one I have for sure, can I use that to program the PIC? Problem on my programmer I only have the DIP socket, is there a cheaper programmer I can buy online or ebay to program the smaller mini surface mount PIC?
    Thanks
     
  13. MLD

    Thread Starter Member

    Dec 7, 2012
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    Bernard,

    Im trying to use as least components as possible and the smallest there is. Forgot to ADD one thing WHAT TURNS THE BUZZER OFF. I might need to add a mini push or slide switch, didn't think of that.
     
  14. AnalogKid

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    What is this for?
     
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  15. GopherT

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    Very good question.
     
  16. MLD

    Thread Starter Member

    Dec 7, 2012
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    Its for a school project.
     
  17. DickCappels

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    Aug 21, 2008
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    We are curious about the purpose the timer will serve.
     
  18. Alec_t

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    How can you guarantee that anyone will be within audible range of a very small buzzer in 3 months time?
     
  19. Bernard

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    After 3 mo., battery might be hurting so maybe beep buzzer 5 sec every minute??
     
  20. MLD

    Thread Starter Member

    Dec 7, 2012
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    Just a school project for building miniture simple countdown timer thats all.
     
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