Help with Dogger food dispenser

Discussion in 'The Projects Forum' started by Dolk, Sep 24, 2007.

  1. Dolk

    Thread Starter Member

    Sep 24, 2007
    10
    0
    Background:
    For a class, my team and I are making a dog food dispenser. We are required to dispense food every 'Y' mins for 'X' seconds.

    The intervals
    00:00 - 03:00 IDLE
    03:00 -03:30 dispense 1
    03:30 - 06:00 IDLE
    06:00 - 06:30 dispense 2
    06:30 - 09:00 IDLE
    09:00 - 09:30 dispense 3

    I have been trying to find a timer, with or without a motor, that can be ran using up to 12VDC. So far I have not been able to find anything that will work. If any of you know of something that can be used I would really appreciate it. The timer can be on a circuit board or just anything.

    Thank you for your help.
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    I typed "electric timer" into Google and found oodles of timers that would work for you.
     
  3. Dolk

    Thread Starter Member

    Sep 24, 2007
    10
    0
    You see any that could be programmed for the intervals i have to use?

    BTW: Once the dog food dispenser is turned on, I can not touch it. So all the times have to be programmed before hand.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Most commercially available timers are over $20.

    But you could use NE555 single timer IC's or NE556 dual timer IC's to do what you're required.

    There are plenty of examples on how to use this IC in the datasheets, which are available all over the web - or you could go to the National Semiconductor site to get it. Google is your friend here.

    To turn on a motor to dispense the dog food (like a screw or similar) you could use the output of the 555/556 to energize a relay. Don't forget to use a diode across the relay's coil to block the spike when the relay de-energizes.
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    This could also be accomplished with a microcontroller or pic of some sort.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Most certainly.

    But it does take a bit more work to get such a thing going - for a first-timer. (pun intended)

    The OP (original poster) would have to learn the programming language, debug the code, build a programming interface, design the rest of the circuit - a bit much for a newbie.

    But with a 555/556 timer, one just has to be able to read the datasheet, and select the proper R/C values to wire in. You can buy everything for just a few bucks at a Radio Shack, if that's the only electronics-related store around.

    Once the OP gets the basics of timer circuits, they can go for the more advanced stuff.
     
  7. Voltboy

    Active Member

    Jan 10, 2007
    197
    0
    You could use a PICAXE microcontroller.
    Its cheap and would handle that code and its easy to program.
    Just search it in google




    -Yoda
     
  8. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    A 556 would work... One side of the chip could be configured as an astable with a period of 3 hours with a 17% duty cycle. The other side could be configured as a monostable, triggered by any 24 hour timer, with a period of more than 6.5 hours but less than 9 hours. Outputs could be ANDed together to achieve the required intervals.

    555s are not too stable with such long periods, but should suffice for a school project.


    Might actually be easier to make a low-voltage switch out of a thrift-store clock face... or use three thrift-store alarm clocks.
     
  9. Dolk

    Thread Starter Member

    Sep 24, 2007
    10
    0
    Thank you for all your help.

    Yes a I am a newb at all this, and I probably will not be able to figure out how to program the chip to do what I want to do. I have looked into this already and tried to find some boards that were already built and could be programmed but things just got to confusing for me.
    I am trying to not be such a big newb, but if someone could direct me to a board already built and easy to programm then that will help me so much. I'll try to find something, but with so little knowledge in this field, i'll have a difficult time.
     
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