pls help me .......how it works....???

Discussion in 'The Projects Forum' started by JITHINSMMB, Mar 13, 2011.

  1. JITHINSMMB

    Thread Starter New Member

    May 17, 2010
    9
    1
    pls help me to find detailed working of the circuit below..........

    it is a circuit used to control the speed of the motor (that drive wiper) with rain intensity .....?

    pls help me ...how the circuit is achieved the motor speed control....
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    The 4017 is a decode counter, The outputs 0 through 9 step sequentially as the input is clocked. Everytime the button is pushed the next output goes high while the others go low. If the input 555 were an oscillator instead of a monostable it would sequence through all the outputs and repeat, I use this effect a lot for light chasers.

    Since this is a rail to rail output (the output is either power supply voltage). Low is a true 0V and high is whatever the positive power supply is. The drive is very low though, you can not pull too much current (very little actually) before the rail to rail characteristic breaks down.

    Since each output isolated via diode, and is feeding a resistor that is part of a frequency select resistor of the second 555 you can vary the speed digitally.

    How much do you know about 555s?

    The 555 Projects

    LEDs, 555s, Flashers, and Light Chasers
     
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  3. JITHINSMMB

    Thread Starter New Member

    May 17, 2010
    9
    1
    pls give me the working of ic3(NE 555) how it controls motor speed
     
  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    He gave you everything you are asking for.

    ???
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    Look at VR1 through VR10. Only one is selected at a time, and is actually part of the second 555 circuit. By varying the resistance on that point of the 555 oscillator you vary the width of the pulse. This is actually a form of PWM, which is very good for controlling motor speeds.

    The 555 circuit is based off this fundimental 555 circuit, which is found in every datasheet I've ever looked at for the 555.

    My Cookbook

    [​IMG]

    For more information how PWM works here is an article I wrote for the AAC book.

    Pulse Width Modulation

    I'm betting this was a school assignment. Hope this information helps.
     
  6. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The very old circuit you found on that website in India does not control the speed of the motor. Instead it controls the duration the wiper motor runs from nearly no time to about 10 seconds selected by the CD4017 trimpot that it stops its sequence on. The off time for each cycle is about 3 seconds. It turns on and off for as long as it runs.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    I didn't do the math for the second 555, it is a very slow oscillator.
     
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