3 Month Countdown

Discussion in 'The Projects Forum' started by riksworld, Oct 25, 2012.

  1. riksworld

    Thread Starter New Member

    Oct 25, 2012
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    Hi All,

    I am looking at making a countdown timer that is set at 3 months to 0 to remind me to change my filter media.

    I did think about using a 555 timer, but over this time period it might prove to be inaccurate.

    The project will be powered by 2 aa or a 9v battery with 2 leds, 1 red and 1 green, the green led will stay on for 3 months, then go off and swop to the red led to indicate its time.

    Ive been searching on google, but its now showing much up, can anyone on here please point me in the right direction.

    Many thanks to all who replys.
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I would use three leds, one for less than month remaining, second for a week for example, and third for overdue. Two aa´s would be better than 9V.
    Lighting a LED for three months is not an easy task on batteries, so maybe the leds should just do short blink each 5 seconds or something, then the last led will stay lit.
     
    Last edited: Oct 25, 2012
  3. riksworld

    Thread Starter New Member

    Oct 25, 2012
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    Thanks for your response.

    The driver could be 12V dc rather then aa batterys if need be.

    Would you have any ideas on a schematic for this type of device?
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I would use somthing like an MSP430 microcontroller and a 32768hz crystal. I can help you with the program, it is pretty easy. And you can get free samples from TI :D
     
  5. riksworld

    Thread Starter New Member

    Oct 25, 2012
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    Thank Kubeek,

    What sort of programmer do you need to flash the MSP430 as I dont have any programmers.

    Whats the address of TI for a free sample
     
  6. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Look here, http://www.ti.com/product/msp430g2231#samplebuy and click on the one in PDIP 14 package. Make a login and pretend you´re some small company.
    Basically you need just a serial connection, do you have an rs232 port on your computer?
     
  7. riksworld

    Thread Starter New Member

    Oct 25, 2012
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    afraid not, all the computers in our house have no serial output, but I might be able to get access to one at work.
     
  8. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Then you just need some more parts and you´re ready.
     
  9. riksworld

    Thread Starter New Member

    Oct 25, 2012
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    I have ordered a free sample and its on its way.

    Could please advise on what other parts are required?
     
  10. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    You need a max3232, 5x 100nF caps, some 3.3 LDO regulator, then the leds and 150ohm resistors to them.
     
  11. riksworld

    Thread Starter New Member

    Oct 25, 2012
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    Could you provide a rough schematic on how to put it together and the software needed please
     
  12. takao21203

    Distinguished Member

    Apr 28, 2012
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    I have never used free samples. I have for instance ordered 50x 16F54, 50x 16f57, 100x 16f1503, 100x 16f1503. And many other PICs. Some were actually resold, so I got money back.

    It's just another way to get "free" components, involving some extra work, and to wait months or even a year or two.

    But maybe, if your "free sample" circuit works, you'd buy other things from them. This is the hope why they offer these samples.
     
  13. takao21203

    Distinguished Member

    Apr 28, 2012
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    You have to make sure the power supply is not interrupted during these 3 months. This will often occur if you use wall adapter.

    1. Use batteries.
    2. Alternatively, use an RTC IC (Real Time Clock IC). Some can be programmed for alarm, but this is not neccessary, the controller can do this.

    You need to look up I2C protocol, and search for "RTC IC" or "I2C RTC".
    Some controller chips have I2C library already included to compiler (under examples).

    For the software if you never used C, you need to learn it. It is quite an empty language, not much to learn. Many compilers will include a set of sample sources, which you can use as a starting point.

    If you decide to use assembler you buy-in a lot of trouble.

    There are also BASIC compilers for some controllers. For your application, you might be able to use a demo version (since it will be a small program).

    The basics how to write the software for a simple microcontroller can be understood within a few hours. Simple controllers are better for this, while large chips can be more difficult to understand.

    You did not write which TI430 chip you are going to use.

    For the TI430 there exists a very cheap USB programmer/evalution kit somewher. One of their smaller controllers.
     
  14. takao21203

    Distinguished Member

    Apr 28, 2012
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