Rotary motor remote control

Discussion in 'The Projects Forum' started by Flavio, Apr 13, 2009.

  1. Flavio

    Thread Starter New Member

    Apr 13, 2009
    I have built a magnetic loop antenna wich has a variable capacitor
    connected across the main loop. In order to move the capacitor CW or CCW
    to tune the antenna to resonance I use a small DC motor and a simple PWM 555 circuit with a DPDT switch to invert the polarity. Although it works I´d like to use two dc motors connected together positive to positive negative to negative, so I can spin the control motor by hand moving the other one on the variable capacitor. It works as long it has no load on it. The variable capacitor is quite heavy to spin using the very small current genereted by the control motor. Is it possible to somehow amplify both positive and negative currents with a simple circuit. The current used by the DC motor is about 300 ma (with load)

    Thank you in advance

    Last edited: Apr 13, 2009
  2. bertus


    Apr 5, 2008

    Did you think about a servo system?
    On the axis of the motor at the antenna there is also a potentiometer.
    This goes to a bridge with on the other side a reference potentiometer.
    The bridge is connected to an ampifier that will detect the difference in the two potentiometers and tries to correct the error.

    Something like in this link:

  3. Flavio

    Thread Starter New Member

    Apr 13, 2009
    Hi Bertus!

    Nice cat! I´m a cat lover too!
    Thank you for answering my question. I´ll take a look on it.

    73 de VE2ZFP