switch off the power if the load increases ?

Discussion in 'General Electronics Chat' started by cheeseboy, Jun 7, 2010.

  1. cheeseboy

    Thread Starter New Member

    Jun 7, 2010
    2
    0
    Hi all,

    I'm new to electronics so forgive me if this is a stupid question.

    I have an electronic car aerial (from a scrapyard) which goes up and down correctly depending on the polarity which I'm switching using a DPDT switch.

    My problem is that the motor runs until the aerial is fully out and then continues to try to run making the motor very hot. Is there something that switches the power off if the motor is working too hard or something like that ?

    If so, can I just put it between the power and the motor and it'll handle the switch off ? Also, will it handle the switching polarity okay ?

    Thanks in advance for any advice you can give me.

    Thanks

    Cheeseboy.
     
  2. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    These motorized "aerials" or antennas are usually all run automatically from a stereos "remote" or "power antenna" output..... When it detects voltage on the blue wire it will automatically go up, and when this voltage is removed (stereo turned off) the antenna will automatically go back down.... and these antennas usually have all the switches and controls built in to it...... if the motor is not stopping when reached any of the limits, I would say the controls are defective....

    Motorized antenna.jpg

    B. Morse
     
  3. cheeseboy

    Thread Starter New Member

    Jun 7, 2010
    2
    0
    Hi, thanks for the reply. I realise that the aerial must at one time have worked in the way you describe, but no it doesn't so I agree that it's defective.

    What I was looking to do was replace the circuit board in the aerial with something which switches off the power if the motor starts working too hard. Is this possible and relatively simple ?

    Thanks again
     
  4. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    You will have to add a couple of limit switches so the motor shuts off when it gets to either position.... I believe sgtwookie has posted a schematic on these forums about controlling a motor with switches and relays....let me see if I can find it....



    ok here is the thread (atleast one of them....) http://forum.allaboutcircuits.com/showthread.php?t=31197
    he has posted many circuits regarding control of a dc motor with relays and switches, check them out and I can almost guarantee you will find what you need....

    B. Morse
     
    Last edited: Jun 7, 2010
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