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  1. Minder

    Stepper motor or Servo?

    I have found the slot detector type much more accurate than the retro-reflective which are OK for rpm detection. But once you get to 17 S.S. sensors then you have to read them all separately without the advantage of series wired that you can achieve with mechanical type, micro switch, reed relay...
  2. Minder

    Stepper motor or Servo?

    You may want to look at as much hardwired and relay logic as possible, you can get micro switches which have the repeatably that you require at that rpm, another advantage is that they can all be wired in series which does get tricky to do with S.S. switches where any more than 4 or 5 outputs in...
  3. Minder

    Stepper motor or Servo?

    With that type of reduction I would not expect to see any over run or back feed. The sensors typically consist of a slot that the 'flag' would travel through and break the beam, a LED emitter one side with a photo transistor the other side. The part number I mentioned earlier has a fairly wide...
  4. Minder

    Stepper motor or Servo?

    Agree, I have used these slot optos recently, Should work for you if needed. http://www.sharpsma.com/webfm_send/1371 Avail from Digikey. If you have access in UK. M.
  5. Minder

    Stepper motor or Servo?

    Things to consider, a stepper motor operates to fixed increments, a servo motor with its PID requirement, could require too much involvement, programably speaking. If you find a DC motor with the maximum reduction that will still give you the required rpm, then this may be a good choice, you can...
  6. Minder

    Stepper motor or Servo?

    I just remembered one method I have used in the past quite successfully to bring power out of a slow turning wheel, was to use a 1/4" phone plug and jack, the jack was mounted to the base and the 1/4" mono plug was used as a pivot on the wheel. . M.
  7. Minder

    Stepper motor or Servo?

    Do you need to keep it in position, IOW is there any load imposed that may make it turn off posn? Although a stepper motor has a natural indent, without gearing it indexes 1.8° a small DC motor with a fairly high gearbox ratio would have quite high resistance to back feeding at rest. One down...
  8. Minder

    PWM Controller Troubles

    If this is one of the $5.00 PWM controllers on ebay, they are typically 555 based and use a Mosfet for the PWM drive, you most likely have blown this, one source of replacements would be Digikey. M.
  9. Minder

    Transformer question

    The transformer is very easy to test and run for a period to see if there is significant heat with no load. The VA is usually determined by the core size which the winding gauge has to conform to. Just from the Pic I would consider a 50va a suitable replacement. M.
  10. Minder

    thyristor vs triac

    A Triac If used on DC has to be commutated off, they are just as readily used in AC such as SCR bridge for one etc.? Also SCR used back to back for AC use to simulate a triac. I guess those that develop them, get to name them.;) M.
  11. Minder

    thyristor vs triac

    GE were the first developer of the Triac after the SCR development (patent 3,275,909), and they termed it a Bidirectional Triode Thyristor. I have the 6th edition of the GE SCR manual, 1st edition 1st pub. 1958. They refer throughout to SCR's and Triacs as thyristors devices.;) M.
  12. Minder

    thyristor vs triac

    Both the GE SCR manual and the RCA manuals both refer to Triacs (bidirectional triode thyristor) and SCR's as part of the Thyristor family of semiconductors. M.
  13. Minder

    Controlling power levels of house electronics

    So you want an alternative to ON or Standby, what other state do you suggest? M.
  14. Minder

    Need help identifying switch

    Although it appears to be 4 posn with off & 1-2-3 posn's LED iluminated? M.
  15. Minder

    Problems with transistor on test circuit (beginner)

    Where did you get the circuit from, BTW? M.
  16. Minder

    Help with controlling a treadmill dc motor controller please.

    I only go by my personal experience and so far have not had a real problem with the Johnson T.M motor in a CNC spindle applications, using pic based PWM controller and rpm feedback. https://www.johnsonfit.com/blog/treadmill_drive_motors_and_the_question_of_horsepower M.
  17. Minder

    Diode bridge

    I am not talking about the BEMF of a device such as a relay or solenoid where when switched off the BEMF is of the opposite polarity, this is a DC motor (other motors also) where when supplied with a Steady DC voltage, as the motor rpm increases it will reach an rpm where the (self) generated...
  18. Minder

    Help with controlling a treadmill dc motor controller please.

    No.1, Johnson are a nice DC motor, in spite of being Chinese. I think I recognize your post from other forums where it was posted. If you cannot decifer the connections still, then a KB controller would work, either the cheaper SCR or the better PWM version. M.
  19. Minder

    Diode bridge

    The inrush current will be very momentary, as soon as the motor turns the BEMF voltage generated opposes the supply voltage until the motor reaches its operating speed where the current will then be minimum and eventually the opposing voltage will almost equal the supply, at which point the any...
  20. Minder

    120 AC to 120 DC

    The I1 & I2 if connected during a stop or reversal, allows the speed pot to remain at a certain level without taking it to zero first, the drive will come up to speed through the set acceleration setting. M.
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