Bridge rectifier

Discussion in 'General Electronics Chat' started by electronewb, Apr 30, 2012.

  1. electronewb

    Thread Starter Member

    Apr 24, 2012
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    oK I'm on to my next project!!! Building a bridge rectifier!! Instead of and AC source can I use a frequency generator?
     
  2. #12

    Expert

    Nov 30, 2010
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    A frequency generator IS an AC source, but it has a bit higher impedance than a small power transformer.
     
  3. electronewb

    Thread Starter Member

    Apr 24, 2012
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    3
    Would this setup work for a bridge rectifier? AC goes to 9 O'clock and 3 O'clock (wave generator with sine wave) and DC should be on 12 O'clock and 6 O'clock reading with my oscilloscope?

    [​IMG]
     
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    Looks OK to me with one caveat if you are using a function generator for the AC input. If the function generator output common lead is earthed and the CRO common lead is also earthed then one of the diodes would be shorted. Check whether the function generator output is floating or not.
     
  5. electronewb

    Thread Starter Member

    Apr 24, 2012
    260
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    It's not a floating ground!!! I have a 120VAC to 7VAC step down transformer That might give me a better result!!
     
  6. #12

    Expert

    Nov 30, 2010
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    Valuable lesson here. The oscilloscope can cause major disasters with a signal generator! When you attach the cable for external sweep, the scope and signal generator share a ground that is incompatible with rectifiers. You must remove the sweep cable and make sure the two do not share a case ground through the third prong of the power cord or by touching each other mechanically.
     
  7. electronewb

    Thread Starter Member

    Apr 24, 2012
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    What do you mean by major disaster? Would lifting the ground on the signal generator help? That might be why I was getting some really funky readings
     
  8. #12

    Expert

    Nov 30, 2010
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    By major disaster, I mean exactly what T N K said in post #4. If both pieces of equipment have a case ground through the third prong of the power cord, the 'scope will short out some of your projects.

    Later, if you try to measure power line voltages or wave forms, the earth connection on the 'scope wil pop the circuit breaker if you connect it to the power side of the line.
     
  9. wayneh

    Expert

    Sep 9, 2010
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    Been there, done it. Ground loops are a pain.

    Also, be aware that your source signal will suffer two diode voltage drops, ~1.4 volts. If the signal is not larger than this, you won't see it.
     
  10. electronewb

    Thread Starter Member

    Apr 24, 2012
    260
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    So what's the best way to setup a signal generator in scope in a shop? 2 separate outlets?
     
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