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Please Help Me I Need A Timer Cecuit

  1. Jun 5, 2004 #1

    XP

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    Hi

    Can You Help Me
    I Need A Timers Cercuit

    @ 1 Hour
    @ 2 Hour
    @ 10 Hour


    Please Help Me
     
  2. jcsd
  3. Jun 5, 2004 #2

    AKG

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    What exactly do you need? Do you mean something like a circuit that does something after 1 hour, 2 hours, and/or 10 hours? I only have experience with simply circuits with 555-timers, but you'd need some huge resistors/capacitors to get a time constant large enough to be 1hr, and at that point you probably won't get something too precise. You could try to create a clock, and add something that would alarm or whatever after an hour (as it changes the value of the hour).
     
  4. Jun 6, 2004 #3

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    thanks for your reply
    exactly i have a light working with 9 volt
    i want to open this light with a simple circuit after
    @ 1 hour
    @ 2 hour
    @ 10 hour

    i am not very good in electronics
    i can do this circuit <but i dont no how to design it
    please help me i need the circuits after one week


    about the huge resistor
    we can connect to resistar or more in series

    not problem if the circuits is not very precise
    i want it precise 95 % or less to 90 %

    thanks
     
  5. Jun 6, 2004 #4

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    it working on a batterys
     
  6. Jun 6, 2004 #5

    dlgoff

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    Use the 555 timer chip (time constant=RC). Using large resistor values (with small caps) will be physically smaller than choosing large capacitor values (with small resistors).

    regards
     
  7. Jun 6, 2004 #6

    enigma

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    Are do you have any experience with (or are you allowed to use) PIC chips?

    You could program one of them to increment a counter based on input from the 555. For example, increment with the 555 set at 1 hour. Once it increments to 10, turn on the light. That way, you could have large times without the elephant sized resistors/capacitors.

    The alternative which would be more difficult to program would be to have a chip with its own internal timers provide all the counting.
     
  8. Jun 6, 2004 #7

    chroot

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    You could always wire up a large ripple counter out of AND gates, use a very slow clock, and wait for a particular code to occur.

    - Warren
     
  9. Jun 6, 2004 #8
    First off, I'd recommend picking up a book called the TTL cookbook. That book has a lot of info about what you need. Secondly, do you know how to program in any language? If so, then learning how to program a PIC would be easy. If you don't know how to program then you can cruise the net and find a prewritten timer algorithm. Third, if you use a PIC or Atmel AVR(I prefer AVR's personally) microcontroller you can build an entire working circuit that draws less current (ie saves battery life) than by using a 555 timer.

    If you do use a 555 timer you're not going to be able to get a stable frequency below 10Hz IMO (super long RC time-constants are difficult to produce accuretly do to leakage and variations in temperature). So, your stuck with a higher frequency and cascaded counters. Set the frequency for the 555 timer to 60Hz and send the 555 timer output to the clock pin to a modulo-60 counter like the maxim ICM7217B. Go through another modulo-6 counter and then a dual decade counter. Cascade one timer from the dual decate to the second. The second counter in the dual decade can then be used to pull any hour increment you want:

    36000 seconds/10 hours
    36000/modulo-60 counter=600
    600/modulo-6 counter=100
    100/decade counter=10
    10/second decade counter=1. Thus, you can pull hour increments form the second decade counter. A little glue logic(and/or gates that turn on at the desired decade counter increment).

    Finally you might want to include a monostable to produce a pulse at the desired time event rather than an hour long on-time.

    Simple projects are never simple but PIC's and AVR's can reduce the overall complexity. With an MCU you could build the entire project using 1 chip, 1 7805 voltage regulator, and one tantalum .1uF decoupling capicitor. A short program and you'd be set.

    Another option would be a ripple counter with built in oscillator http://www.semiconductors.philips.com/acrobat/datasheets/74HC_HCT4060_CNV_2.pdf . You'd still have to set up a cascaded counter array to derive the desired timing events, but using a counter w/ built in oscillator would elliminate at lease 1 external counter chip.

    Good luck.
     
    Last edited: Jun 6, 2004
  10. Jun 8, 2004 #9

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    i have not A time to learn all that
    i need the circuit after 4 day :frown:
    please give me the three circuit diagram that i need
    i need a ready circuit diagram
    and i am going to learn how to design a timer circuit after one week
    please any one help me :frown:
     
  11. Jun 8, 2004 #10

    chroot

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    Sounds like you really need to go visit your professor at his office hours, XP. Begging for someone to do your homework for you is not going to work well here.

    - Warren
     
  12. Jun 8, 2004 #11

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    i dont have a professor
    :confused:
    i am learning on the net
     
  13. Jun 8, 2004 #12

    Cliff_J

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    XP its simple. The 555 can create regular pulses. A modulo-counter divides those pulses down to a smaller number. You can then invert this number (1/n) and then find how long a period of time that number represents.

    Its that simple. Faust9 gave a good example, re-read it.

    Cliff
     
  14. Jun 9, 2004 #13

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    can you draw the circuit for me please :frown:

    thanks for your reply :smile:
     
  15. Jun 9, 2004 #14

    Cliff_J

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    If you need someone to draw the circuit that is an indication.

    We all start out knowing nothing. There are steps we all take in acquiring more knowledge and understanding however gradual or dramatic. I know I have maybe 5% of the knowledge I'd like to have and probably never will as I find more things to learn about with each new discovery. Its like the more you know, the more you know about what you don't know yet.

    If you are not quite to the level where you can design your own circuit, there are many avenues to pursue instead. Many ready-to-assemble kits and circuits with full circuit board plans exist. Start there. Then start breadboarding your own circuits, start reading the datasheets.

    We all want to start with a something massively impressive like a F16 or Forumla 1 race car or space travel vehicle as our first step. But its far more productive to start with small appropriate sized goals and work our way to those destinations.

    Start with some already designed circuits. Learn them inside and out. Improve them piece by piece, add auxillary functions. Then design simple ones from scratch. You could do this as fast as you want, but there is a progression there. Asking someone to do all the work for you is not a step. But a question about how to do something or why something didn't work is good, very good. I hope you understand the distinction.

    Good luck.
    Cliff
     
  16. Jun 9, 2004 #15

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    i am going to learn how to design the circuit
    put i need the circuit after 3 day to four day
    i cant learn all that in 3 day :cry:
    i need the circuit diagram for my product
    i need your help now
     
  17. Jun 9, 2004 #16

    enigma

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    Seriously. You've been given all you need.

    There is this wonderful invention called "www.google.com". If you're not familiar with it, you really shouldn't be taking an online course.

    Plugging in "555 timer diagram", and the very first hit gives you this website.

    It details the innards of a 555 chip. It details standard wiring techniques and how they work. It even lets you input the resistance and capacitance values and it outputs the time of the output pulse.

    Forum Rules: You must at least try the problem first. We will not do the problem for you. That is called cheating. It's also just shooting yourself in the foot because you aren't learning it. We've done the problem already. Us doing it for you doesn't teach you anything.

    I'm bumping this thread to homework help.
     
    Last edited: Jun 9, 2004
  18. Jun 10, 2004 #17

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    thanks for the circuit ( that's what i need)
    thank you verymuch enigma :smile: :wink:
    ----------------------
    thank you all for your reply :wink:
     
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