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Thread: Steering wheel buttons

  1. #1
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    Jan 2009
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    Steering wheel buttons

    I need to do something a little different. I need my steering wheel buttons to control relays - one button / one relay. What component do I need?

    The buttons send the signal over a single wire. I am pretty sure that it is digital. Would it be easier if it were analog (each button different resistence)?

    thanks, I can't find the answer anywhere...

  2. #2
    Variable Bitrate
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    Jan 2006
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    Hi Jarda, welcome

    How have you determined that the signal is digital?

    It might be easier if it was analog because there are circuits you can buy premade that can interpret those resistances. You can then programme a function for each resistance. I'm not sure how you would do it if the signal is digital, but it is something worth looking into, because in future the steering wheel signals may all be digital.

    Regarding the relays, I've noticed in many cars, if not all, that the headlights (or sometimes only the high beams) are controlled by a relay. When you turn the light switch, you might hear a click from your fuse box/relay box, and you'll also hear it when you turn the lights off. If you can work out how that circuit is connected, you may be able to replicate it for your steering wheel controls. I'm not sure how the digital signal would fit in here, though.

  3. #3
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    Hello,
    I think the signal is digital, because I have disassembled the buttons and there is a board with a microcontroller underneath them.

    If the signal is really digital, I need to create my own board with a microcontroller and a voltage regulator. The press of a button will then send a digital command to my microcontroller, and the microcontroller will determine the right output pin and route the impulse to this pin. The voltage regulator will then convert it to 12V and that's it.

    So there's a solution for my first question, I did some research in the past days and this is what I came up with.

    My second question was - if the signal from the steering wheel was in fact analogue - would the converting to separate 12V lines be easier? Without the need for a microcontroller?

  4. #4
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    Further research shows, that the connection between the steering wheel buttons and the MFL unit is indeed digital.
    It uses a U6050b unit described in detail at http://www.datasheetcatalog.org/data...c/mXyzurtr.pdf

  5. #5
    Variable Bitrate
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    Which microcontroller do you plan on using to decode your digital signal?

    Are you going to use a pre-made voltage regulator or are you going to make your own?

  6. #6
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    The best and easiest way to decode would be using a U6052B demultiplexer described in the document. Its purpose is to decode the signals sent by the U6050B and operate separate relays for each button, which is exactly what I need.

    The problem is, that these parts are very hard to find. I found a couple on eBay, but the prices are high and I would have to pay for shipping to Europe.

    If I don't find the demultiplexer, I have two options
    a) program my own microcontroller
    b) disassemble the MFL unit and take the parts from there

    The problem with b) is that the U6052B in the MFL unit is an SMD part. I would need professional tools to disassemble the board and reuse it. This option still seems to be the easiest, so I will have to talk to somebody more experienced about it.

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