Help please on a reverse polarity circuit without switches (Car speakers that popup)

Discussion in 'The Projects Forum' started by muzchap, Oct 20, 2015.

  1. muzchap

    Thread Starter New Member

    Oct 20, 2015
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    Hi,

    Firstly, it's been about 25+ years since I last undertook a 'proper' electrical project (and that was at school!)

    I have some B&O speakers from an Audi that I'm trying to retrofit in another car - they are probably controlled by the Amp (which I don't have)

    Putting 5v on to the motor extends the speakers out, reversing the polarity brings it down. There are 3 wires (well 5 - 2 are speakers) going to the device, Pins 1+2 (pin 1 + pin2 - ) cause it to extend and (pin 1 - pin 2 +) cause it to retract. I have tried bridging between pins 1+3 and pins 2+3 to see if that would prompt anything (with pin 1+ and pin2 -)

    I believe the motor has a cut-off built in as it doesn't sound like it's straining at the end of travel.

    Ideally, what I'd like to happen using the P-con wire from the headunit is - ignition on - energise the speaker UP, on ignition off, energise the speaker down.

    Now I'm only using 5v - I have tried increasing the voltage but 5v gives the smoothest action on the motor and mechanism.

    So I would also need to drop the 12v down to 5v

    ---

    My rambling idea...

    I think I will need a permanent feed to two relays and the ignition switched power to the relay so that when the ignition is on Pin 1+ and Pin 2-, when ignition is off, I need the relays to switch to Pin1- and Pin2+. I hope that makes sense. I have googled around and I have seen diagrams showing something similar with switches - I guess I just need the P-con wire from the headunit to be the pseudo switch.

    I can post photo's if needed and happy to shout anybody willing to help some beer tokens via PayPal :)
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Sounds like a single DPDT relay would do the direction switching.

    You might want to add a 5V power supply that turns on when the headunit is turned on, and it delays about 10sec turning off after the headunit looses power, either because it was switched off, or because the ignition key was turned off. The delay would give the speakers time to retract after the ignition key was turned off as the car is parked.
     
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  3. muzchap

    Thread Starter New Member

    Oct 20, 2015
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    Hi Mike,

    Many thanks for your answer :)

    In terms of supplying the 5v - I was thinking of re-using one of the many old phone car chargers I have laying around as they have a MC34063 regulator, which would be more efficient and less risky than a pure resistor. I was hoping to tap into the interior lights as they tend to do exactly what you suggest - stay on for x seconds after ignition off. However the vehicle is canbus - so will have to be careful where I do this.

    In terms of the DPDT relay - I don't suppose I could trouble you further for some wiring up tips?

    I have wired normal 4 pin relays in (again because of canbus) for a reversing camera - in the old cars, you could tap off the power of the 12v rail when the reverse light was engaged, but due to Canbus, that is no longer sufficient, so I had to run a permanent live and use the reverse light to switch the relay, so the camera received the true 12volts.

    But - unfortunately, that's pretty much the limitations of my relay wiring experience :(


    My assumptions here - are I will need 2 power inputs:

    1) Live as discussed above with a delay
    2) Live from the headunit on power on (again running through a phone charger)
    3) Earth (obviously)

    Now it's the switching over I can't quite get my head around :(

    I also found this relay:

    http://www.maplin.co.uk/p/10a-dpdt-miniature-relay-12vdc-n08aw

    Looks like it could be fine for my intended use?

    I'll google some wiring diagrams now - see if I can make sense of them

    I found this:

    http://www.learningaboutelectronics...a-double-pole-double-throw-relay-in-a-circuit

    So in theory - I'm fine feeding 12v into the relay from the car electronics - it's just on the NO/NC rails I would need to drop the voltage down to 5v using my repurposed phone charger electronics :)
     
    Last edited: Oct 20, 2015
  4. muzchap

    Thread Starter New Member

    Oct 20, 2015
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    Hmm - I've been looking further and is it really this simple? I don't think it can be :(

    COIL 12v feed from Head Unit +
    COIL 12v feed from Dimming Light + (Time delayed)
    COM Earth
    COM Earth
    NO Speaker Motor + (with dropdown to 5v)
    NO Speaker Motor -
    NC Speaker Motor -
    NC Speaker Motor + (with dropdown to 5v)
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
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  6. muzchap

    Thread Starter New Member

    Oct 20, 2015
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    Hi Mike,

    It really is a tiny little motor - I think the power supply I am currently using one of those variable 1.5v - 12v things only kicks out about 700ma.

    I have attached some pics - as they should help - please keep clicking and zooming in - as you'll see the text notes I have made on them.

    Cheers :)

    [​IMG]

    [​IMG]

    [​IMG]
     
  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Here is how I would do it: Using a LM7805 to make the 5V, has a delay circuit that produces 5V for about 10sec after the Head-end signal goes away, either because you turn off the Head-end, or you turned off the key. Speakers pop out only after Head-end is turned on. The limit switches inside the motor are reached before the timer times out.

    The circuit has input from the battery so that it can retract the speakers after key is turned off. Steady-state, key-off battery drain is ~1ua of leakage.

    131.gif
     
  8. muzchap

    Thread Starter New Member

    Oct 20, 2015
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    0
    Mike

    Looks great Thank you so much - will sit down and work out that diagram as it's a bit over my head at the min :)

    Will do some research - build it and report back :)
     
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