TIP142 Stepper motor driver

Discussion in 'The Projects Forum' started by crazybuoy, Oct 3, 2010.

  1. crazybuoy

    Thread Starter Active Member

    Sep 19, 2010
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    Now, I have try this circuit with 24V DC, 1.7Amp power supply. But still the motor does take any step (forward or backward). I think the value of resister is very much big. What it should be?
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    I presume the -24 Volts in your schematic is a ground connection.
    Are you using Back-EMF diodes on the motor windings?
    If you are not using them the transistors may be dead by now.

    Bertus
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    What are you using to drive the inputs to the bases?

    If a logic level (say, 0v=0ff, 5v=on), then you need to calculate the base resistors using that lower voltage.

    Rbase = (Vin - 1.4v) / 10mA (this is specifically for the TIP14x with up to 5A collector current)
    Rbase = (5-1.4) / 0.01
    Rbase = 3.6/.01 = 360 Ohms.

    If you are switching the inputs using 24v, then:
    Rbase = (24-1.4)/10mA = 22.6/0.01 = 22.6k Ohms. You could use 22k or 23k.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Bertus,
    The TIP14x series have body diodes which would take care of the reverse EMF.

    However, using external reverse EMF diodes is a good idea, as it reduces the power dissipation in the transistor body.
     
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    @ SgtWookie,

    I see it in de datasheet that there are diodes in the transistors.
    What I also see is that the different manufacturers have different resistors accross the two bese emittor connections.

    [​IMG]

    Fairchild shows 120 Oms for R2.
    ST shows 60 Ohms for R2 and
    ON shows 40 Ohms for R2.

    Is this off influence of the base current?

    Bertus
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    Switching transistor aside, it would be interesting to know how and in what sequence the transistors get switched.
     
  7. crazybuoy

    Thread Starter Active Member

    Sep 19, 2010
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    0
    Thanks, then are there some good articles. Please provide me some links. I know, that I can also search but can not think which is batter one.
     
  8. crazybuoy

    Thread Starter Active Member

    Sep 19, 2010
    62
    0
    Now following stepper driver is successful to run the steps of motor. But there is a problem that the transistors turn hot very quickly. What is problem here. I think the resistor is small. Is it?
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    Darlingtons get hot because they have a high Vce(sat); the output transistor never truly saturates like individual bjt's do (bjt=bipolar junction transistor).

    Replacing the Darlingtons with logic-level MOSFETs would help the situation enormously.

    IRLZ24, IRLZ34, IRLZ44 N-ch power MOSFETs are pretty common.
     
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