Using automatic car aerial not in a car

Discussion in 'The Projects Forum' started by Trickyone, Aug 11, 2009.

  1. Trickyone

    Thread Starter New Member

    Aug 11, 2009
    2
    0
    Hi guys,
    First, thanks for any help you can give. This is really appreciated.

    I am trying to use an automatic car aerial to create a gadget where a sign will rise when a button is pushed. I have the footswitch and the aerial but I am having trouble getting the aerial to work. Details of the aerial can be found here:
    http://www.maplin.co.uk/module.aspx?TabID=1&criteria=usb&ModuleNo=5141&C=SO&U=Strat15

    what I really need to know is:

    a) What powersource can I use and can I avoid having to buy a full car battery?
    b) should this be as simple as rigging the green wire to the negative and the red to the positive via a switch and fuse, or am I missing something

    Thanks again for any help you can give. I look forward to hearing your replies
     
    Last edited: Aug 11, 2009
  2. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    Yes, it should be a simple project. For a power source, you'll need to know the current draw of the motor. If this isn't specified on the packaging, you'll have to measure it with an ammeter. A cheap digital multimeter should be adequate for this. In the US, Harbor Freight sells a model for under $5.

    The power source can probably be a "wall-wart" that can supply the current you measured. It sounds like all you'll have to do is connect the power leads to the wall wart properly, then connect the positive lead through a normally open switch to the control line that raises and lowers the aerial.
     
  3. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    Its a simple circuit with a switch, a motor and a supply. What problem are you having? Also please indicate the current ratings for the aerial and whether you need to do anything for it to go down after raising it, like reversing polarity.
     
  4. Trickyone

    Thread Starter New Member

    Aug 11, 2009
    2
    0
    Thanks for your responses guys. The issue I am having is that the aerial has a circuit within it that controls the automated rise when a radio is switched on. This is achieved by attaching one wire from the aerial to the positive and the other wore to the on-off switch on the radio. That is according to the instructions. I can't see therefore how it will have any power to go in reverse when it is turned off. But my main issue is that it doesn't seem to tart at all when hooked up to batteries that supply 12v 5amps.
     
  5. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    It might have a battery wire to always supply it with 12v to do that.
     
  6. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    Did you follow the instructions given on the web site you gave? The red and black lines get +12 VDC and ground, respectively. The green wire will cause the aerial to go up when +12 V is put on it and go down when it is grounded (it might be the opposite; the site doesn't really say -- but it's easy to find out by experiment).
     
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