Filter capacitors

Discussion in 'General Electronics Chat' started by hang glider, May 27, 2009.

  1. hang glider

    Thread Starter New Member

    May 27, 2009
    Reviving old thread, hoping to acquire some assistance -
    Same problem, I need to determine the size of a smoothing capacitor.

    I have no electrical experience, (other than wiring a couple of houses) but I have recently picked up a 130V DC gearmotor that I need to use.

    A full-wave bridge rectifier (Radio Shac) should convert 120 house current, but to smooth the output, I'm trying to calculate the size capacitor. Motor draws .91 amps

    If ripple voltage is 10% average, would this work?
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Buddy . Please start a new thread and we will answer. it's not nice to impose you know. :)
    And that capacitor will go pooooooooooooooooooooooof! :D
    and will emit smoke. cause the DC Voltage when when rectified by 120 VAC mains will give you 170V DC approx. and if you are driving motors I suggest you get the capacitance value above 1000uf
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    We prefer to have a new thread started, rather than reviving an old one. This is the original thread -

    Working with line voltage without an isolation transformer is lethally dangerous. There is absolutely no way to make the circuit safe. You must use some means to provide galvanic isolation from the line.

    Your motor would need a transformer with a secondary of about 90 volts to give the 130 VDC after rectification and filtering. Motors don't care much about smooth DC, so use a 250 volt rated capacitor of a 1000 uF capacity.

    You must use a step down transformer for safety.