Motor reversing device with timer

Discussion in 'The Projects Forum' started by pakun, Apr 9, 2008.

  1. pakun

    Thread Starter New Member

    Apr 8, 2008
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    I have a project that needs me to build a autonomous car. im trying to build a device or circuit that would make my motor run forward for a certain amount time , then runs in the opposite direction for certain time and stop without any switches involved. I need an idea of wat parts to use and how the circuit looks like.. ive thought of reverse polarity n stuffs but i have little knowledge about electronics.so any advice or suggestion would be helpfull....thank u
     
  2. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
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    If you want to get into autonomous stuff, you'll need some sort of intelligent and dynamic way to control your motor. I recommend looking into a microcontroller of some sort, personally, I use the PSoC from Cypress Microsystems. A lot of people use PIC though, some use AVR, etc.

    You would control a motor's direction by reversing current flow. This is commonly accomplished via a h-bridge circuit. Google it and you'll learn more about it.

    Steve
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    Wait - that's it?
    Just start up and run forwards for a while, then (perhaps) coast or brake to a stop, then back up for another period of time, and then stop - either coasting or braking?

    No steering involved or anything - just time delays between events?
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    For the forward and reverse trick, you'll want to study a circuit called an "H Bridge." Web pages on the subject abound, and a search should get you started learning quickly.

    For the timing trick, you'll want to study a circuit called a "monostable multivibrator." Again, an internet search on that exact term will yield a lot of helpful material.
     
  5. pakun

    Thread Starter New Member

    Apr 8, 2008
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    yea...i juz want my car to go forward for like 10 seconds...stop...go backwards for another 10 second and stop. all this action activated with only one button or flick. i wont wanna go into programming, so the H-bridge would probably do the job. i was juz wondering about the monostable multivibrator, is it a part of the h-bridge or a seperated circuit? is there any other simpler timer circuit which would do the job?
    thx guys..
     
  6. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    The monostable multivibrator generates an output state of controlled duration. It is about the most simple timing circuit there is. You can use one, triggered by your pushbutton, to make the H Bridge run one way for ten seconds. You can use the falling edge to trigger a second monostable making the H Bridge run the other way for ten seconds.

    Here is an example of a simple monostable multivibrator: http://www.antonine-education.co.uk...od2/topic_2_2/topic_2_monostable_circuits.htm
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    Attached is a timer circuit you could use.

    It's just two CMOS IC's with several potentiometers, resistors, diodes, and a capacitor or two. Note that you don't HAVE to use potentiometers to adjust the times; once you find the correct resistance for the time you want, you can substitute fixed resistors. For the diodes, you could use all 1N4148's or any small signal silicon diode.

    Power connections to the ICs are not shown. Note that you must also use bypass capacitors across each IC's power connections; 0.1uF ceramics or tantalum would work well.

    You could use the "spare" gates on the 4093 to control an H-bridge.
     
  8. pakun

    Thread Starter New Member

    Apr 8, 2008
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    ive done some research but still going no where for my project..im juz wandering for the timer circuit.. will a 555 timer circuit do the job? coz for that i can buy the whole timer circuit set from shops around.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    Did you look at the circuit I posted?

    For the 4093, you could substitute a 40106, or another Schmitt-input 4000 series CMOS device that had an inverting output.
     
  10. thingmaker3

    Retired Moderator

    May 16, 2005
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    A pair of 555s (or a 556) will work, but not by themselves.
     
  11. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
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    Wookie posted a perfect solution to your problem! You can either make an h-bridge from discrete parts using logic level FETs, since it is the easiest discrete method for you. You can get a fully integrated h-bridge that will work a bit nicer in a smaller package.

    People are too afraid of microcontrollers these days! Sadly, if you do not jump on the programming band-wagon, you'll find yourself unemployed as an electrical engineer, sad as it is...

    Steve
     
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