Bnc connector adapter with built in diode??

Discussion in 'General Electronics Chat' started by magnetman12003, Nov 12, 2009.

  1. magnetman12003

    Thread Starter Active Member

    May 10, 2008
    31
    0
    Hi All,

    I have a Function generator supplying square wave power to an experimental electric motor I am working on.

    The generator output can be damaged by the back EMF of the motors coils. So far that has not happened.

    The generator has BNC connectors. I have been using 1,000 volt diodes on the front of alligator clips to keep the motors back EMF spikes from damaging the generators output
    .
    Does anyone know if a BNC adapter is made that incorporates protection diodes within it? I can do away with clipped diodes this way.

    For sale I see small BNC coaxial adapters that protect against lightning strike surges??
    I just wonder if they are worth cosidering for my needs.

    Tom
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I haven't seen them, but no big deal to make them yourself.

    Just get a BNC "T" connector, and wire up a male or female solder-type BNC connector with an EMF suppression diode; and plug it in.
     
  3. magnetman12003

    Thread Starter Active Member

    May 10, 2008
    31
    0
    Someone suggested to place a "Series string" of twelve 2.5 volts in "parallel" with my function generator output. (My generator is capable of 30 volts peak to peak max.) Then another series but "REVERSED" string the same way as above.

    So we are looking at 24 WHITE 2.5 volt leds total.

    Claims that the back EMF from a coil powered from the generator will damage the generator output.-- Thats true. - BUT - If those lights are in place they will light up when any Back EMF voltage is OVER 30 volts. Thereby absorbing the Back EMF and changing it into light.

    The lights will never come on at any generator output lower than 30 volts??

    Is all of this true or nonsense? LEDs are dirt cheap.

    Tom
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    The Vf of LEDs varies with current applied. They are rated for a typical Vf at a specific current. However, they will provide some light at a lower Vf.

    You're better off using a Zener back to back with a standard rectifier diode; make two of those and wire them in opposite polarity but parallel. They'll do the snubbing for you.

    You could also add a low-voltage MOV in case the Zeners fail.
     
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