car folding mirrors

Discussion in 'The Projects Forum' started by maff, Oct 29, 2007.

  1. maff

    Thread Starter New Member

    Oct 29, 2007
    4
    0
    Hi, i have recently got some electric folding mirrors, but really puzzled with how to wire them the way i would like them to operate.

    Each mirror has 2 wires, when wired to positive and negetive the mirror opens, when reversing polarity they close.

    I would like them to open automatically when my alarm is disarmed (unlocked) and close when the alarm is armed (locked). However the alarm output is simply one wire which is a ground-when-armed output.

    Also, i would like a switch so that i can close the mirrors if i need to drive through a tight space.

    The mirror operation needs to be on a timed circuit to avoid burning the motors out.


    Here is a diagram i found on another site:


    http://img86.imageshack.us/img86/8883/pwrmirrorcntltk0.png

    I'm not sure if it will work, i need to change the unlock and lock input triggers shown (i could wire like the diagram, but wouldn't the mirrors fold in if a had to lock the doors while driving?). I will have just one neg when armed (lock) output from my alarm. how do i split this to go to the unlock and lock triggers in the diagram?

    and finally where/ how can i add a switch?


    Or, any better ideas would be very gratefully recieved.
    Thanks, Matt
     
  2. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    A transistor bridge is what I have in mind, or a relay bridge, as they are more reliable. 2 SPDT relays are enough for such bridge.
     
  3. maff

    Thread Starter New Member

    Oct 29, 2007
    4
    0
    i did a search and came up with H bridge relays, is this what you meant?
    sorry my electrical knowledge is really poor, but i'm have fun trying to learn.

    To make my single ground-when-armed wire split into 2, that one wire will have ground-when-armed and the other wire will have ground-when-disarmed, what do i need to do?

    thanks

    I'm going down to the local scrap yard to see if i grab loads of relays, switches etc, so i can start playing around. It's ok trying to see it work in my head, but i need to actually see how these things work together, i'll learn better then (hopefully!).
     
  4. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    Yes, I meant H bridge. I was trying to remember the name. An accurate term would be a DPDT (double pole, double trow) relay. You can ose one of these relays as an inverter. It replaces the two SPDT relays I mentioned after. Since I don't fill like using Visio I'll post an hand drawing.

    Edit:
    Here it is.
    scan.jpg
     
  5. maff

    Thread Starter New Member

    Oct 29, 2007
    4
    0
    thanks! i'll give that a try on the weekend :)
     
  6. maff

    Thread Starter New Member

    Oct 29, 2007
    4
    0
    Hi, i couldn't get hold of a DPDT relay, so ended up getting 2 SPST? ones instead. I thought i could make it work, but it didn't. Here is what i did...
    http://www.box.net/shared/qqopq8e52z

    I thought that with the coil energised it would move the motor one way, then when they are not energised the relays would switch and motor would reverse. Currently it will only go one way, energised or not.

    What am i doing wrong?
    Also, when testing the mirrors, it seems that they don't have limit switches in them. So i think i need to time the motor movement so they don't burn out. I was looking at using this kind of module:
    http://www.maplin.co.uk/module.aspx?ITAG=FAQ&ModuleNo=220009&doy=28m10#faq
    What do you think?

    Thanks!
     
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