speed

Discussion in 'Programmer's Corner' started by wes, Feb 3, 2008.

  1. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
    2
    hey i need to know how fast something like a basic stamp can excute a program. I need to it to be able to do it about every 1-10 milisec. is that possible and how fast could something like a pc with a intel pentium 4 3Ghz do it, it's for a motor and i need the program to read a sensor and then turn a electromagnet on when the sensor is on
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Can you tell us more details on what you are planning to do with the electromagnet?

    It sounds like you want to control the strength of the magnetic field as a function of a sensor. If that interpretation of your question is correct then I think you may want to consider the use of PWM control over the magnetic field strength.

    hgmjr
     
  3. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
    2
    Hi, the EM is supposed to go from a high power mode to a lower power mode and the reason is because when you turn a EM off when using DC it creates a back spike kinda like a inductor when power is turned off and so i thought that if you just dont turn it off completly and still have it on but in a low power mode then maybe you wouldnt have that back spike. (if i am wrong then please tell me) . the EM is going to be used in a motor idea i have.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The EM will have a self-induced reverse voltage when the driven field collapses. To keep the high voltage spike out of the drive circuitry, you can put a diode across the EM coil, so it conducts and shorts the reverse voltage. Or you can use a snubber, which is a capacitor and resistor in series across the coil. The diode is probably the easiest to use.
     
  5. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
    2
    hey i'm am a little confused about the part of the magnetic field collapseing, for example, now if instead of turning the power off, you just lower the voltage or which i was going to do was increase the resistance to decrease the current but never completly turn it it off, so the EM would have something like 1- 10 milli amps flowing, would you still have a back- emf or is it just the fact of lowering the power from the orignal which creates the back-emf, so it doesnt matter whether you turn it off or not ????

    :confused:
     
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