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  1. Minder

    Clamping circuit for PIC A/D

    Trying to keep a high impedance load to the source. 200μa! M.
  2. Minder

    What type of wire is copper wrapped around fluffy threads?

    I found that the heat from an iron melts the covering and burns off the 'tinsel' I repaired one that way just recently. M.
  3. Minder

    Clamping circuit for PIC A/D

    A schottky bridge followed by a 2n7000 with a input to a high speed opto with a output pulled up to 5v for input to the Picmicro. M.
  4. Minder

    Clamping circuit for PIC A/D

    If this is just a go/no-go situation, a 2n7000 and an opto isolator may do it. M.
  5. Minder

    Clamping circuit for PIC A/D

    So ~20v rms if it is a constant, at what frequency? What do you intend to do with the signal? A small ferrite transformer may do it depending on the frequency and small bridge rect.. M.
  6. Minder

    Current sensor for arduino

    Similarly the ACS712 is $1.50 on ebay with board and terminals. 112275500486 M.
  7. Minder

    I need a equivalent of an integrated circuit.

    If this is some kind of custom controller, you may have to re-engineer using a Pic or other micro. M.
  8. Minder

    Small dc motor speed control

    One method here for fixed speed, including code. https://www.romanblack.com/onesec/DCmotor_xtal.htm For feedback of a DC or BLDC motor you need something like this. M.
  9. Minder

    Zero Crossing Point Detector .....

    The BLDC servo drives I use only require the BLDC hall effect commutation devices or the equivalent on an encoder track. These are principally ±10vdc command type, they will run in open loop (variable speed) or velocity type drives but at low RPM cogging is evident due to the coarse commutation...
  10. Minder

    Zero Crossing Point Detector .....

    One popular method for industrial BLDC servo's etc is to initially exercise the motor and detect the location of rotor poles by BEMF, from then on the rotor is kept track of by a encoder on the motor shaft. The industrial drives I use that are H.V. (>200vdc) typically use Mosfet bridge...
  11. Minder

    Wanted: linear actuator 12/24V 6-7" extension 30-50lbs,fast 10mm/s

    I suspect you are going to need some degree of customization, a off the shelf solution may be hard to come by.! M..
  12. Minder

    Pottery Wheel refurbishment - updating components

    Would it be a Variac style controller? On this side of the pond, often KB drives or ex T.M. units are used, You could make a simple 555 based PWM unit with Mosfet output, or even use a Triac dimmer style ceiling fan control followed by a bridge rectifier. Wound Shunt field motor = 4 connections...
  13. Minder

    Pottery Wheel refurbishment - updating components

    That is a VERY small motor.! The O/L is only rated at 1amp. M.
  14. Minder

    Pottery Wheel refurbishment - updating components

    Yes you can pick up cheap Telemecanique contactors and O/L's on ebay. You just need to reverse engineer the function on the original O/L. That IS an old motor if it has a wound field. In some cases a field loss detector is used to avoid the motor taking off uncontrollably if it loses the field. M.
  15. Minder

    Looking for a component

    One suitable device would maybe a SmartRelay, they have a real time clock option. There are a few manufacturers, some just re-labeled. They are a miniature version of an industrial PLC. M.
  16. Minder

    Pottery Wheel refurbishment - updating components

    That appears to be a remote trip type, or at least an alarm contact output. That is a small motor, you could probabally either use a 2 terminal device or even a fuse. Do you have any circuit or schematic of the unit to indicate the aux function? M.
  17. Minder

    Alternative for a relay or switch, switching a 12V 23A motor?

    IGBT-Mosfet? M.
  18. Minder

    Relation between pwm frequency and motor speed

    And this is a pdf showing the relationship between the winding and the hall sensor, the motor is being back-fed (generating). This is what you need to do when aligning an encoder with hall tracks to the relative stator winding. It requires a D.B. 'scope. M.
  19. Minder

    Alternative for a relay or switch, switching a 12V 23A motor?

    You could also look at using a IGBT, most do not include the BEMF protection so a diode would be needed. How difficult would it be to switch the neg side? M.
  20. Minder

    Relation between pwm frequency and motor speed

    Couldn't open the XLS file. The BLDC motor is controlled very similar to the DC brushed, IOW to increase rpm, the degree of energy is increased to the armature. In the case of PWM you have a basic switching frequency, for a motor application the suggested minimum is 4.5Kh to 5Khz to avoid...
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